An overview of heavily polluted landfill leachate treatment using food waste as an alternative and renewable source of activated carbon

Accepted Manuscript Title: An overview of heavily polluted landfill leachate treatment using food waste as an alternative and renewable source of activated carbon Author: Areeb Shehzad Mohammed J.K. Bashir Sumathi Sethupathi Jun-Wei Lim PII: DOI: Reference:

S0957-5820(15)00167-6 http://dx.doi.org/doi:10.1016/j.psep.2015.09.005 PSEP 618

To appear in:

Process Safety and Environment Protection

Received date: Revised date: Accepted date:

24-3-2015 2-8-2015 5-9-2015

Please cite this article as: Shehzad, A., Bashir, M.J.K., Sethupathi, S., Lim, J.W.,An overview of heavily polluted landfill leachate treatment using food waste as an alternative and renewable source of activated carbon, Process Safety and Environment Protection (2015), http://dx.doi.org/10.1016/j.psep.2015.09.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Highlight for Review Food waste is a renewable source of AC. Activation conditions have a great effect on AC adsorbent characteristics. AC is a prominent in landfill leachate pollutants treatment. Converting waste into AC may overcome food waste disposal problem. Opportunities and challenges concerning AC productions and implementations.

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An overview of heavily polluted landfill leachate treatment using food waste as an alternative and renewable source of activated carbon Areeb Shehzad1, Mohammed J.K. Bashir 1,*, Sumathi Sethupathi1, Jun-Wei Lim2 1

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Department of Environmental Engineering, Faculty of Engineering and Green Technology (FEGT), University Tunku Abdul Rahman, 31900 Kampar, Perak, Malaysia. 2

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Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia

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*Corresponding Author: [email protected]; Tel: 605-4688888 ext: 4559; Fax: 6054667449

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Abstract

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Landfill leachate is a complicated refractory wastewater which contains huge amount of

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organic compounds and ammonia. Recently, the adsorption technology exploiting on activated carbon has gained promising importance in the treatment of landfill leachate due to its

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simplicity in design and low preparation cost of activated carbon in addition to high treatment efficiency. In this study, the physical and chemical characterizations of fabricated activated

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carbon derived from renewable sources such as food waste were highlighted to shed a brighter understanding on their performance in removing pollutants from landfill leachate. The impacts

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of activating conditions, such as carbonization temperature, retention time and impregnation

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ratio were thoroughly studied and compared between conventional and microwave heating

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methods. The significance of the produced food waste derivative-based activated carbon is expected to contribute towards a sustainable environment by overcoming the ramification of landfill leachate menace particularly via the removal of non-biodegradable organic compounds. Conclusively, the expansion of food waste in the field of adsorption science represents a potentially viable and powerful tool, leading to superior improvement of pollution control and environmental conservation.

Keywords: Landfill leachate; Adsorption; Activated carbon; Food waste; Microwave and conventional heating

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1.0 Introduction Owing to the ravage of uncontrolled pollution in the 21st century, environment is no longer a serene or stable but rather becoming much unrecognizable. Solid wastes, virtually defined as

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discarded solid materials generated from combined residential, industrial and commercial activities in a certain region, is directly interlocked with pollution calamities which seriously

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inflict the nature aesthetics. The poor indiscriminate management of solid waste continues to

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be a major predicament encountered by the world, particularly in the rapidly growing cities of the developing countries (Manaf et al., 2009; Ngoc et al., 2009). The setbacks soar due to the

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destitute of technical support, unhinged of financial stability and haphazard of institutional, economic, and social planning which constrain the development of effective solid waste

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management systems. Foo and Hameed (2009) indicated that the municipal solid waste is indeed the major problem of today, creating a paradox between the rate of production of

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industrial products and generation of waste quantities. There are many options available for

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handling of municipal solid waste, namely via open dumping, incineration, gasification, sanitary landfill, grinding and anaerobic digestion, etc. (Foo and Hameed, 2009).

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Conventionally, the world is more concerned about applying cost-effective methods for the disposal of solid waste. Historically, landfill measure had been the most popularly employed method for solid waste disposal and is still subsisting in many regions around the world. The long-standing problem associated with municipal landfill is the self-generation of highly contaminated leachate (Aziz et al., 2013; Abu Amr et al., 2013; Zhang et al., 2013). The landfill leachate properties continue to be dangerous and poisonous to the adjacent habitats over long period of time. And so, removal of contaminants has become an imperative concern in leachate treatment over recent decades (Rafizul and Alamgir, 2012; Zhang et al., 2013). Nevertheless, leachate generated from old landfill site is more complex as compared to that generated from new landfill site as it is practically impossible to be effectively treated via

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biological processes (Abu Amr et al., 2013; Mohajeri et al., 2010). Various methods, such as precipitation, adsorption, oxidation, evaporation, reverse osmosis and ion exchange have been exercised to remove diverse pollutants originated from old landfill leachate (Bashir et al.,

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2012&2013; Abu Amr et al., 2014). Adsorption process is one of the most effective methods used for the treatment of broad range of wastewaters (Halim et al., 2012; Bashir et al., 2014;

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Azmi et al, 2015). Adsorption using activated carbon (AC) is considered to be one of the most efficient technologies for the removal of color, nitrate, chemical oxygen demand (COD) and

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heavy metals. AC is a form of carbon processed to have small, low-volume pores that increase

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the surface area available for adsorption or various chemicals. AC illustrates significant adsorption efficiency in gas and liquid phases due to its high micropore volume, large specific

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surface area, favorable pore size distribution, thermal stability and capability for rapid adsorption and low acid/base reactivity (Bansal et al., 1988; Li et al., 2009). Hence, AC has a

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great capability to remove essential amount of organic compounds and inorganic compounds

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such as ammonium nitrogen and metal ions from the leachate (Foo and Hameed, 2009; Mojiri et al., 2014; Azmi et al., 2015).

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In light of the above-mentioned review, the present work serves to analyze and

evaluate the recent published literature mainly from year range of 2004 - 2014 associated with landfill leachate treatment via low cost adsorbent prepared from renewable resources, i.e, food waste. This study is not only focusing on the preparation conditions of AC, but also investigates on the optimum performance in terms of adsorption capacity and removal efficiency of the prepared AC in eliminating contaminants, such as chemical oxygen demand (COD), color, NH3-N and heavy metals from the leachate. The future opportunities and challenges concerning AC productions and implementations in adsorption process are as well discussed herein.

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2.0 Landfill leachate Characterization and Treatment

Municipal landfill leachate is a liquid that become polluted whilst percolating through the

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waste within the landfill site (Bashir et al., 2010). The liquid medium absorbs the nutrients and contaminants from the waste will crowd out as a leachate, capable of inflicting the adjacent

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environments. The composition of landfill leachate varies from region to region; however, depends mainly on nature of deposited wastes, soil characteristics, rainfall patterns and age of

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landfill (Visvanathan et al, 2004; Tsarpali et al., 2012). Generally, the quantity of leachate is

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direct linked with the external water volume that enters into the landfill site (Visvanathan et al, 2004). Bashir et al. (2012) asserted that the generation of highly contaminated leachate can

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seep into the ground and contaminate the groundwater, surface water, and soil. Elementary management tool is essential to conceive the leachate characteristics at a specific site. Figure 1

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clearly demonstrates the overall process of leachate formation. Landfill leachate has a lasting

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impact on environment as it continually produces leachate and releases biogas even after many years of closure (Primo et al., 2008). Typically, the leachate can be characterized into three

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major groups as shown in Table 1. These groups are mainly organic matters, inorganic matters and xenobiotic organic compounds (Lee et al., 2010; Renou et al., 2008; Kjeldsen et al., 2002). The characteristics of the landfill leachate can be best signified by the COD, color, NH3-N and heavy metals contents which serve as the main chemical features of environmental threats (Rafizul and Alamgir, 2012; Bashir et al., 2014). Bashir et al. (2013) reported that as the landfill aging, the biological decomposition of deposited waste will reduce and leachate will become more stable due to the present of bio-refractory compounds, viz., fulvic acid and humic acid. According to Kulikowska and Klimiuk (2008), the concentration of heavy metals in a landfill is generally higher at earlier stages because of higher metal solubility but it will decrease with the landfill age as the solubility of many metal ions decreases with the increase

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in pH. The heavy metals mainly present in leachate are Cu, Zn, Pb, Cd, Hg etc. Lead is the only heavy metal whose concentration increases with the increase in pH as it forms very stable complexes with the humic acids. The soaring concentrations of COD and NH3-N, resulted

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from the decomposition process of organic matters, are considered as the primary cause of acute toxicity to the living organisms (Bashir et al., 2014). In general, young leachate

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possesses high COD (>5000mg/L) and low NH3-N (<400mg/L) concentrations. In contrary to this, old leachate has greater concentrations of NH3-N as compared with COD (Visvanathan et

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al., 2004). Table 2 classifies three different types of leachate according to the landfill age

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(Alvarez et al., 2004; Irene and Lo, 1996; Chian and DeWalle, 1976). The concentration of COD is considerably higher in young landfill leachate as compared with old landfill leachate

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which primarily consists of non-biodegradable organic compounds. Accordingly, the biodegradable factor of leachate plummets as the age of landfill increases. Thus, the

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conventional biological treatment methods will have inconsequential impact on the

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decontamination of landfill leachate (Huang et al., 2008; Li et al., 2009). Nevertheless, the treatment of young leachate via biological techniques can yield a reasonable removals with

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respect to BOD, COD, NH3-N and heavy metals (Aziz et al., 2010 and 2012; Renou et al., 2008). On the flipside, when the treatment of stabilized leachate is considered, physicochemical approaches are found to be more suitable in removing refractory substances. With the continuous strengthening of the discharge standards in many countries and ageing of landfill sites producing increasingly stabilized leachates, the conventional treatments are insufficient to fulfill the level of discharge requirement. As a result, enormous efforts focus on solving these problem have been intensified, leading to the various leachate treatment techniques being documented in recent decade (Figure 2)

3.0 Adsorption Treatment Process

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Different processes have been used for the treatment of landfill leachate, e.g, chemical oxidation (Rivas et al., 2003), adsorption (Cecen et al., 2003), chemical precipitation, coagulation/flocculation (Rivas et al., 2004), dissolved air/flotation, air stripping, membrane

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filtration, microfiltration, ultrafiltration, nanofiltration and reverse osmosis (Bashir et al., 2013, 2014). Each of these processes and others has its own advantages and disadvantages.

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The combination of biological and physical–chemical processes is being recognized as the most effective technology for manipulation and management of high strength effluents (Renou

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et al., 2008; Bashir et al., 2014). The integrated process ameliorates the drawbacks of

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individual process thus, contributes to a higher efficacy of the overall treatment. In this viewpoint, adsorption process is extolled to be easily retrofitted into any integrated process

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with low cost involved.

Adsorption is a surface phenomenon in which a multi-components fluid (gas or liquid)

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mixture is attracted to the surface of a solid adsorbent to form attachments via physical or

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chemical bond (Sasaki et al., 2014). The material providing the solid surface is termed as adsorbent while material removed from the liquid phase is known as adsorbate. Tiny chemical

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particles suspended in another phase of matter, meaning in the air as a gas or in water as a liquid, are sometimes considered contaminants. These tiny particles can be separated from those phases via adsorption process, bonding onto solid phase (Lenntech, 2014). Thus, decontaminating the air and liquid phases. A noted rising trend of the usage of this technique in recent decade is due to the vast production of AC adsorbent. This type of adsorbents (AC) possesses high porous surface area, thermo-stability and superior ability to remove a wide variety of organic and inorganic pollutants dissolved in aqueous media (Foo and Hameed, 2009). The adsorption of pollutants onto AC in columns provides better reduction in COD levels than the chemical treatment methods. This has greatly enhanced the probability of using

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adsorption process in removing the high levels of organic compounds exist in leacate (Renou et al., 2008). However, in many cases adsorbent’s cost is one of the crucial and important criteria to

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peer in to check the economic feasibility of the treatment process. To top it off, numerous side factors are also responsible for the limited use of adoption technique such as precursor cost for

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preparing AC, the final material (sorbent) which include its availability, processing required, treatment conditions, and both recycling and lifetime issues (Bhatnagar et al., 2013). Other

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drawback is the need for frequent regeneration of columns or an equivalently high

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consumption of powdered activated carbon (PAC). Although reconciliation on several drawbacks had been done, yet this phenomenon is getting considerable important and certainly

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great progress is to be expected in the future. Moreover, the adsorption technique has surprisingly turned into a valuable tool in recent decade; from an alternative process by

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offering a numerous of advantages for the removal of various contaminants. In view of world

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human population growth, the production of food waste would presumably ascent proportionally. Therefore, the utilization of food waste as a feedstock could plausibly

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overcome the drawback due to cost.

4.0 Preparation of Activated Carbon (AC)

Typically, the activated carbon preparation is carried out via the following sequencing steps, i.e., pretreatment of the material, impregnation of material with activator, carbonization of the impregnated material and removal of the activator.

4.1 Material Pretreatment

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Prior to the carbonization process, pretreatment of the raw material is required. Preliminary treatment of crushing, milling and sieving for appropriate particle size are important for subsequent handling of the raw material (Alslaibi et al., 2013a). Appropriate particle size is

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crucial in the mixing and impregnation process with activator (Alslaibi et al., 2013a). The finer the particle size the greater it will be in studying the characterization and activation

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effect. Recent documented results have shown the effect of particle sizes on the activation process. Shalabay et al. (2006) examined the properties of apricot stones. Three particle size

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ranges were examined, namely 0.85 to 1.7 mm, 1.7 to 3.35 mm and 3.35 to 4.00 mm. The

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results showed the finest particle increased the density of micro-porosity. During the process of carbonization, the raw material will undergo thermal decomposition under the inert

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atmosphere through gasification by nitrogen gas. The carbonization process can be executed within the tubular furnaces, reactors, muffle furnaces and more recently in a glass reactors

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placed in a modified microwave oven (Lim et al., 2009). The process termed as pyrolysis

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which greatly removes hydrogen, nitrogen and oxygen elements from the material, leaving a simple carbon structure behind. The temperature, flow rate and heating rate are generally the

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fine-tuning factors in which the pyrolysis process is depended. Slow heating rate will generally turns the material into char residue while flash pyrolysis will give higher liquid production (Renou et al., 2008).

4.2 Activation Processes

Physical (oxidizing agents of CO2 or steam) and/or chemical (mineral salts) activation methods are frequently being used for the production of AC.

4.2.1 Physical Activation

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Physical activation is normally executed via carbonization followed by activation under partial or controlled gasification at high temperature. Activation completed through gasification using oxidizing agent or its mixtures at temperature ranging from 700 to 1100oC will produce high

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porosity (micropores and mesopores) carbonized material. The use of CO2 will yield narrow micropores, while steam will widen the initial micropores (Shalabay et al., 2006).

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Accordingly, CO2 helps to produce larger volume of narrow micropores while steam creates larger volume of mesopores and micropores. Table 3 presents the various activating agents

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used in various activation methods in the preparation of AC.

4.2.2 Chemical Activation

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Chemical Activation with Conventional Heating: During the chemical activation, the precursor is impregnated with an activating agent such as ZnCl2, H3PO4, KOH, H2SO4 or

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NaOH. And then, carbonized following conventional heating via an electrical furnace in an

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inert atmosphere at temperatures ranging from 400 to 800oC or alternatively carbonized with microwave heating (Demiral and Gunduzoglu, 2010). The impregnation ratio, activation

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temperature and activation time period were observed to be the vital factors in preparing AC from conventional heating. The impregnation ratio (defined as the ratio of the weights of chemical agent to precursor) is a variable that highly affects not only the pore size distribution of the resulting AC, but also the total surface area (Fierro et al., 2007). Table 4 illustrates the optimal conditions for preparing AC via conventional heating with the noted activation temperature and time fall in the ranges of 450 - 900 oC and 1 - 3 hr, respectively. To the best of our efforts in reviewing the literature, it was found that the impregnation with alkaline hydroxides (KOH and NaOH) would result in achievable of high specific surface area with the range of 2318–3500 m2/g (Tseng, 2006). To top it off, increasing the impregnation ratio would generally increase the total surface area. Nevertheless, the disadvantages of

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chemical activation approaches include high costs of activating agents and the need for an additional washing stage to remove the chemical agent. The total surface area was as well increasing with the spiral of activation temperature and retention time to the threshold levels

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of each and after which it decreased. Several authors had reported that ACs prepared under vacuum conditions produced slightly better results in terms of Brunauer–Emmett–Teller

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(BET) surface area and pore volume than those produced under N2 gas atmosphere (Tseng,

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2006).

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Chemical Activation with Microwave Heating: Typical carbon materials are generally good microwave absorbers. Thus, the demand of microwave technologies has been considerably

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amplified in the recent years particularly for AC preparation. This process is being exploited in the synthesis of different kinds of carbon materials, e.g., graphite, active carbons, polymers,

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etc. Due to their microwave-assisted thermal behavior, the produced carbon materials have

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very wide range of applications either in pilot plants or in industrial sectors. Table 5 shows the optimal conditions for preparing AC using microwave heating. Impregnation ratio, activation

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power and activation time frame were the primarily factors for consideration while preparing AC via microwave heating. It could be epitomized that the most common ranges of operational experimental conditions for the preparation of AC derived from food wastes by chemical activation with microwave heating were radiation power of 350 - 700 W and radiation time of 5 - 15 min. Microwave leads to the development of relatively higher surface areas of produced AC as compared with conventional heating for the same precursor used (Guo and Rockstraw, 2007). Due to rapid rise of radiation temperature, it shortens the time of activation which reduces the energy consumption. Chemical activation with microwave heating is easier to operate than the conventional heating and it also leads to the development

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of high surface area which enhances the rate of adsorption and removal efficiency of hazardous materials (Alslaibi et al., 2013b).

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5.0 Food Waste as a Renewable Source of AC Production for Leachate Treatment Undoubtedly, food waste can be used as a renewable source for the production of AC. The

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advantages of using the food waste may possibly minimize the land consumption for food waste disposal and to convert the waste into a value-added product (Azmi et al., 2015). Any

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low-cost material constitutes of high carbon and low in-organic contents can be used as a raw

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material for the production of AC. Food waste had been proved to be a promising raw material for the production of AC due to their ease of availability and capability to produce AC with

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high adsorption capacity, considerable mechanical strength, and low ash content (Savova et al., 2001). As being highlighted earlier, literature survey indicates that there have been many

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attempts to treat several types of wastewaters including leachate by using prepared low-cost

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AC or adsorbent derived from food waste sources such as wheat, corn straw, olive stones, pinecone, rapeseed, cotton residues, olive residues, sugarcane bagasse, almond shells, peach

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stones, grape seeds, straw, oat hulls, corn stover, apricot stones, cherry stones, peanut hull, nut shells, rice hulls, corn cob, corn hulls, hazelnut shells, pecan shells, rice husks, rice straw, banana peel, durian peel, coffee, tamarind, etc (Skodras et al., 2007). Landfill leachate treatment efficiencies for the removal of contaminants using adsorbents prepared from food waste are demonstrated in Table 6. The adsorption capacities and removal efficiencies of the contaminants (COD, color, NH3-N, and heavy metals) from landfill leachate are being experimented and recorded with respect to the leachate initial characteristics, adsorbent preparation conditions, treatment methods and operating conditions of treatment. The preparation of banana frond derived adsorbent was carried out using KOH as an activating agent and later treated using microwave heating. The resulted AC material was exploited to

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remove boron and iron metal ions from landfill leachate. The effects of adsorbent dosage, initial pH, contact time and temperature were identified to be the main influencing factors impinging the adsorption process (Foo et al., 2013a). The carbonization process was carried

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out at 700 oC and the resulted char was mixed and impregnated with KOH solution. The adsorbent dosage, initial pH, contact time and temperature factors were simultaneously

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optimized, leading to the maximum adsorption capacities of total boron and iron ions of 97.45% and 95.14%, respectively, by banana frond activated carbon (BFAC) (Foo et al.,

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2013a). Data revealed in Table 6 have proved that a low contact time of 10 min was sufficient

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for the adsorption process to reach the equilibrium state, which hinted its economical feasibility for real application (Foo et al., 2013a). However, the adsorption capacity and

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removal efficiency of heavy metals depend largely on the leachate initial characteristics and operating conditions of treatment.

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Coffee grounds waste was used to prepare AC for the removal of total iron and

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orthophosphate (PO4-P) from landfill leachate (Ching et al., 2011). The adsorption capacity of total iron increased with increasing of the adsorbent dosage. But for the PO4–P removal,

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fluctuation trend was observed due to the effect of foreign ions presented in the leachate. The prepared durian peel (DP) activated carbon demonstrated high surface area with welldeveloped porosity. Kamaruddin et al. (2011) substantiated that DP activated carbon could be utilized as the substitution of commercial activated carbon for semi-aerobic landfill leachate. Conventional heating activation was carried out and very high surface areas were attained thereafter. Generally, increasing the temperature and retention time of activation will enlarge the surface area. They found that almost 42% of COD and 40% of color could be removed under the conventional treatment method with activation time of 2.1 hr. Also, the maximum adsorption capacities of COD and color were determined as 61.72 mg/g, 100 Pt-Co/g, respectively (Kamaruddin et al., 2011).

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Palm shell activated carbon used as a media for visualizing the flow inside an adsorption column (Lim et al., 2009). The adsorption column was designed to see the occurrence of fluctuations COD removal. The effluent concentration never reached the influent COD

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concentration due to unification of solutes. This implied a possibility of biological activity in the column in which the activated carbon served as support media for the attachment of

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degrading bacteria from leachate. After monitoring carefully, empty bed contact time (EBCT) and pH had no influence on the turbidity of the leachate. The maximum adsorption capacity

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and removal efficiency of COD were 1460 mg/g and 50%, respectively (Lim et al., 2009).

Foo et al. (2013 b, c) examined the preparation methods of AC derived from tamarind fruit

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and sugarcane baggase. The effect of impregnation ratio with KOH impregnating chemical was studied. The N2 was used as an activating agent with induced microwave activation

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process. The activation time with microwave heating was confirmed to be relatively shorter

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than the conventional heating method and the yield of AC was high. The activation power and impregnation ratio of chemical were ascertained to exert the greatest effects on the yield of

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these food waste-based AC (Foo et al., 2013c). Also, their results revealed that both of these factors did strike the micro and mesopore volumes as well as the BET surface area which had good adsorption capacities for the removal of COD, color and NH3-N. The maximum removal efficiencies of NH3-N and COD by tamarind fruit-based AC were 91.23 and 79.93%, respectively (Foo et al., 2013b). The adsorption of NH3-N and orthophosphate onto sugarcane baggase was conveniently explained by their isothermal model with a monolayer adsorption capacity of 138.46 and 12.81 mg/g, respectively (Foo et al., 2013c). These findings demonstrated the applicability of tamarind fruit- and sugarcane baggase-based ACs for the adsorption treatment of landfill leachate.

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Azmi et al. (2015) studied the performance of sugarcane baggase-based ACs in treating landfill leachate. They reported that removal of color, COD, and NH3-N were well described by Langmuir isotherm model, with a maximum monolayer adsorption capacity of 555.56

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Pt/Co, 126.58, and 14.62 mg/g, respectively. The optimum experimental conditions resulted in 94.74, 83.61, and 46.65% removal of color, COD, and NH3-N, respectively.

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Xie et al. (2014) proposed Orange Peel AC to deal with effluent of landfill leachate after biochemical treatment. About 59.7 of Total organic carbon (TOC) was removed at the proper

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preparation conditions of Orange Peel AC (i.e., 550 oC reaction temperature, 3 IR, and 1hr

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reaction time). Halim et al. (2011) investigated the performance of a new composite adsorbent prepared from rice husk carbon waste (75 % w/w), commercial activated carbon (8.22% w/w),

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and ordinary Portland cement (16.78% w/w). The results indicated that percentage removals of

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COD and NH3-N were 27.61 and 51.0, respectively.

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The AC derived from food waste can remove significant amounts of organic compounds and NH3-N from leachate. However, the complexity of the leachate composition and variation in

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leachate characteristics from site to site makes it even more challenging to formulate general recommendation.

6.0 AC Production Capacity and Future challenges

World demand for AC is projected to rise 8.1% per year to 2.1 million metric tons in year 2018. North America will remain the largest AC market; however, the Asia-Pacific region will slightly outpace and overtake North America by year 2023. The global AC industry was estimated to be 1.1 million metric ton in 2013 (Freedonia, 2014). According to Freedonia (2014), nearly 80% of total AC is consumed by the liquid phase applications, i.e, wastewater

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treatment. A phenomenal increase in the demand of AC happened from the year 2003 to 2013. Figure 3 shows the amount of AC demand from 2005 and forecasted for year 2018 (Freedonia, 2014). The consumption of AC is higher in US and Japan which together consumes two to

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four times more than Europe and other Asian countries. As shown in Figure 4, the per capita consumption of AC per year is 0.5 kg in Japan, 0.4 kg in US, 0.2 kg in Europe and 0.03 kg in

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the rest of the world (Freedonia, 2014).

With reference to the above-mentioned, ACs are of interest to many industries. Roskill (2013)

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anticipated that the world consumption of AC would double in four years, i.e., from year 2013

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to 2017. Hence, sustainable production of AC throughout the world is necessary. Commercial AC is produced from various carbonaceous precursors such as lignite and coal (~ 42%), peat

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(~10%), wood (~33%) and coconut shell. It is inevitable that the usage of AC derived from food waste will be priority for many countries as it will reduce the landfill footprint earmarked

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for this waste material disposal. Thus, at the present time, the agricultural by-products and

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food waste are preferably used as feedstock for manufacturing AC. This is due to their abundance, commercial availability, low cost and low in inorganic composition, besides

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constituting high carbon content. Literature survey indicates that there have been tremendous efforts to fabricate low-cost AC or adsorbent from food waste. Unfortunately, AC production capacity from wastes cannot be identified due to a gap of information in literature vis-à-vis this issue (Ioannidou and Zabaniotou, 2007).

Concerning leachate treatment via adsorption process using AC derived from food waste, some works had been carried out. However, as indicated in Table 6, the numbers of published results are still relatively small, these results attained thus far are promising and there is undoubtedly a need for more details of systematic studies. Moreover, information on

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economic aspects related to the conversion of food waste to AC for the purpose of landfill leachate treatment is not much available and requires intense investigations.

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7.0 Conclusions The production of AC derived from food waste is important from both environmental and

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economical viewpoints. The processing and transformation of this waste into AC would lay a

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foundation to eliminate the problems of disposal and management of food waste materials, while providing a value-added end product for water and wastewater treatment that could

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potentially expand the carbon market. The type of food waste materials, activating agents and processing conditions play a vital role in determining the property of fabricated AC. The

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advantages of chemical activation with microwave heating application is greatly outweighing the conventional heating, demonstrated by low energy consumption, short preparation time

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and high removal efficiency of pollutants. Owing to the extreme consumption of AC,

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sustainable production of effective AC throughout the world is urgently required. Thus, the usage of AC derived from food waste should be admonished to reduce quantity of food waste

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disposed to landfill, while provide a renewable source of AC.

Conflict of Interest: The authors declare that they have no conflict of interest.

References:

Abu Amr, S.S., Aziz, H.A., Adlan, M.N., 2013. Optimization of stabilized leachate treatment using ozone/persulfate in the advanced oxidation process. Waste Manage. 33 (6), 14341441.

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Abu Amr, S.S., Aziz, H.A., Bashir, M.J.K. (2014) Application of response surface methodology (RSM) for optimization of semi-aerobic landfill leachate treatment using ozone. App. Water Sci. 4, 231-239.

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Alslaibi, T.M., Abustan, I., Ahmad, M.A., Foul, A.A., 2013a. Production of Activated Carbon from agriculture byproduct via conventional and microwave heating. A review. J. Chem

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Technol. Biotechnol. 88, 1183-1190

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Alslaibi, T.M., Abustan, I., Ahmad, M.A., Foul, A.A., 2013b. Application of response surface methodology (RSM) for optimization of Cu2+, Cd2+, Ni2+, Pb2+, Fe2+, and Zn2+ removal

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te

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d

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Aziz, S.Q., Aziz, H.A., Yusoff,M.S., Mojiri, A., Amr, S.S.A., 2012. Adsorption isotherms in landfill leachate treatment using powdered activated carbon augmented sequencing batch reactor technique: Statistical analysis by response surface methodology. Int. J. Chem.

ip t

Reactor Eng. 10, 1–21. Azmi, N.B., Bashir, M.J.K. Sethupathi, S., Ng, C.A., 2015. Anaerobic stabilized landfill

cr

leachate treatment using chemically activated sugarcane bagasse activated carbon:

us

kinetic and equilibrium study. Des. Water Treat. DOI: 10.1080/19443994.2014.988660. Bansode, R.R., Losso, J.N., Marshall, W.E., Rao, R.M., Portier, R., 2004. Pecan shell-based

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wastewater. Bioresour. Technol .94, 129-35.

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d

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te

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Ac ce p

exchange resins in different mobileion forms on semi-aerobic landfill leachate treatment, Water Sci. Technol. 63, 641–649.

Bashir, M.J.K., Aziz, H.A., Yusoff, M.S., Aziz, S.Q., 2012. Investigation of color and COD eliminations from mature semi-aerobic landfill leachate using anion-exchange resin: Equilibrium and kinetic study, Environ. Eng. Sci. 29, 297–305.

Bashir, M.J.K., Aziz, H.A., Aziz, S.Q.,Abu Amr, S.S., 2013. An overview of electro-oxidation processes performance in stabilized landfill leachate treatment. Des. Water Treat. 51, 2170–2184.

Page 20 of 41

Bashir, M.J.K., Aziz, H.A., Abu Amr, S.S., Sethupati, S., Ng, C.A., Lim, J.W., 2014. The competency of various applied strategies in treating tropical municipal landfill leachate. Des. Water Treat, DOI:10.1080/19443994.2014.901189

ip t

Bhatnagar, A., Hogland, W., Marques, M., Sillanpaa, M., 2013. An overview of the modification methods of activated carbon for its water treatment applications. Chem.

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Bonelli, P.R., Della Rocca, P.A., Cerrella, E.G.,Cukierman, A.L.,2001. Effect of pyrolysis

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temperature on composition, surface properties and thermal degradation rates of Brazil

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Bouchelta, C., Medjram, M.S., Bertrand, O., 2008. Preparation and characterization of activated carbon from date stones by physical activation with steam. J. Analyt. Appl

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.Pyrolysis 82, 70–77.

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Cao, Q., Xie, K.C., Lv,Y.K., Bao, W.R., 2006. Process effects on activated carbon with large

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specific surface area from corn cob. Bioresour. Technol. 97, 110-115 Caturla, F., Molina-Sabio, M., Rodriguez-Reinoso, F., 1991. Preparation of activated carbon by chemical activation with ZnCl2. Carbon. 29, 999-1007

Cecen, F., Erdincler, A., Kilic, E., 2003. Effect of powdered activated carbon addition on sludge dewaterability and substrate removal in landfill leachate treatment. Advances Environ. Res. 7, 707-713.

Chian, E.S.K., DeWalle, F.B., 1976. Sanitary landfill leachates and their treatment, J. Environ. Eng. Div. 411–431.

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Ching, S.L., Yusoff, M., Aziz, A., Umar, M., 2011. Influence of impregnation ratio on coffee ground activated carbon as landfill leachate adsorbent for removal of total iron and orthophosphate. Desalination. 279, 225-234.

ip t

Demiral, H., Gunduzoglu, G., 2010. Removal of nitrate from aqueous solutions by activated

cr

carbon prepared from sugar beet bagasse. Bioresour Technol.101, 1675–1680.

Din, M.A.T., Hameed, B., Ahmad, A.L., 2009. Batch adsorption of phenol onto

us

physiochemical-activated coconut shell. J. Hazard. Mater. 161, 1522–1529.

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Fierro, V., Torne-Fernandez, V., Celzard, A., 2007. Methodical study of the chemical activation of Kraft lignin with KOH and NaOH. Microp. Mesop. Mater. 101, 419-431

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Freedonia., 2014.World Activated Carbon Available at:www.Freedoniagroup.com/World Activated Carbon - [Accessed 17 Nov 2014].

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Foo, K., Hameed, B., 2009. An overview of landfill leachate treatment via activated carbon

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adsorption process, J. Hazard. Mater. 171, 54–60.

Ac ce p

Foo, K., Hameed, B.H., 2011. Factors affecting the carbon yield and adsorption capability of the orange peel activated carbon prepared by microwave assisted K2CO3 activation.

Chem. Eng. J. 180, 66–74.

Foo, K., Hameed, B., 2012. Coconut husk derived activated carbon via microwave induced activation: effects of activation agents, preparation parameters and adsorption performance. Chem. Eng. J. 184, 57–65 Foo, K., Lee, L.K., Hameed, B., 2013a. Preparation of banana frond activated carbon by microwave induced activation for the removal of boron and total iron from landfill leachate. Chem. Eng. J. 223, 604-610.

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Foo, K., Lee, L.K., Hameed, B., 2013b. Preparation of tamarind fruit seed activated carbon by microwave heating for the adsorptive treatment of landfill leachate: A laboratory column evaluation. Bioresour Technol. 133, 599-605.

ip t

Foo, K., Lee, L.K., Hameed, B., 2013c. Preparation of activated carbon from sugarcane bagasse by microwave assisted activation for the remediation of semi-aerobic landfill

cr

leachate. Bioresour Technol. 134, 166-172

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Ganan, J., Gonzalez, J., Gonzalez-Garcia, C., Ramiro, A., Sabio, E., Roman, S., 2006. Carbon dioxide-activated carbons from almond tree pruning: Preparation and characterization.

an

Appl. Surface. Sci. 252, 5993–5998.

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Girgis, B.S., Yunis, S.S., Soliman, A.M., 2002. Cereal Straw as a Resource for Sustainable Biomaterials and Biofuels. Mater. Lett. 7, 57- 164.

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Guo, Y., Rockstraw, R.A., 2007. Physicochemical properties of carbons from pecan shell by

te

phosphoric acid activation. Bioresour. Technol. 98, 1513–1521.

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Halim, A.A., Abidin, N.N.Z., Awang, N., Ithnin, A., Othman, M.S., Wahab, M.I., 2011. Ammonia and COD removal from synthetic leachate using rice husk composite absorbent. J. Urban & Env. Engg. 5, 24–31.

Halim, A.A., Aziz, H.A., Johari, M.A.M. Ariffin, K.S., Bashir M.J.K., 2012. Semi aerobic Landfill Leachate Treatment Using Carbon-Minerals Composite Adsorbent. Environ. Eng. Sci. 29 (5) 306-312

Huang, Q., Yang, Y., Pang, X., Wang, Q., 2008. Evolution on qualities of leachate and landfill gas in the semi-aerobic landfill, J. Environ. Sci. 20, 499–504.

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Ioannidou O, Zabaniotou A (2007). Agricultural residues as precursors for activated carbon production - A review. Renewable and Sustainable Energy Reviews 11: 1966-2005. Irene, M., Lo, C., 1996. Characteristics and treatment of leachates from domestic landfills.

ip t

Environ. Int. 4, 433–442.

cr

Kalderis, D., Koutoulakis, D., Paraskeva, P., Diamadopoulos, E., Otal, E., Olivares del Valle J, I., Fern´andez-Pereira, C., 2008. Adsorption of polluting substances on activated

us

carbons prepared from rice husk and sugarcane bagasse. Chem. Eng. J. 144, 42-50

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Kamaruddin, M.A., Yusoff, M.S., Ahmad, M.A., 2012.Treatment of semi-aerobic landfill leachate using durian peel-based activated carbon adsorption- Optimization of

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preparation conditions. Env. Eng. J. 3, 223-236

Kjeldsen, P., Barlaz, M., Rooker, A., Baun, A., Ledin, A, Christensen, T., 2002. Present and

te

Sci. Technol. 32(4), 297-336.

d

Long-Term Composition of MSW Landfill Leachate: A Review. Critical Rev. Environ.

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Kulikowska, D., Klimiuk,E., 2008. The effect of landfill age on municipal leachate composition. Bioresource Technol. 99, 5981-5985.

Lenntech., 2014. Water Treatment solution:

Adsorption / Active Carbon. Available at:

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Lee, A.H., Nikraz, H., Hung,Y.T., 2010. Influence of Waste Age on Landfill Leachate Quality. Int. J. Environ. Sci. Develop.1 (4),347-350 Li, H.S., Zhou, S.Q., Sun, Y.B., Feng, P., Li, J.D., 2009. Advanced treatment of landfill leachate by a new combination process in a full-scale plant, J. Hazard. Mater. 172, 408– 415

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Lim, Y.N., Ghazaly-Shaabana, M.D., Yinb, C.Y., 2009. Treatment of landfill leachate using palm shell-activated carbon column: Axial dispersion modeling and treatment profile. Chem. Eng. J. 209, 86-89

ip t

López de Letona Sánchez, M., Macías-García, A., Díaz-Díez, M.A., Cuerda-Correa, E.M., Gañán-Gómez, J., Nadal-Gisbert, A., 2006. Preparation of activated carbons previously

cr

treated with hydrogen peroxide: study of their porous texture. Appl. Surface. Sci. 252,

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Mohajeri, S., Aziz, H.A., Isa, M.H., Bashir, M.J.K., Mohajeri, L., 2010. Influence of fenton reagent oxidation on mineralization and decolorization of municipal landfill leachate, J.

d

Environ. Sci. Health A 45, 692–698.

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Mojiri, A., Aziz, H.A., Zaman, N.Q., Aziz S.Q., Zahed M.A., 2014. Metals removal from

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municipal landfill leachate and wastewater using adsorbents combined with biological method. Desalin Water Treat. 1-14

Nakagawa, Y., Molina-Sabio, M., Rodrıguez-Reinoso, F., 2007. Modification of the porous structure along the preparation of activated carbon monoliths with H3PO4 and ZnCl2.

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Ngoc, U.N., Schnitzer, H., 2009. Sustainable solutions for solid waste management in Southeast Asian countries. Waste Manage. 29, 1982-1995. Petrov, N., Budinova, T., Razvigorova, M., Parra, J., 2008. Conversion of olive wastes to volatiles and carbon adsorbents. Biomass Bioenergy 32, 1303–1310

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Primo, O., Rivero, I., Ortiz., 2008. Photo-Fenton process as an efficient alternative tothe treatment of landfill leachates. J. Hazard. Mater.153, 834–842. Rafizul, I.M., Alamgir, M., 2012. Characterization and tropical seasonal variation of leachate:

ip t

Results from landfill lysimeter studied. Waste Manage. 32, 2080-2095

cr

Renou, S., Givaudan, JG., Poulain, S., Dirassouyan, F., Moulin, P., 2008. Landfill leachate treatment: Review and opportunity, J. Hazard. Mater. 150, 468–493.

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leachate. J. Environ. Sci. Health., Part A, 38(2), 371-379.

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sequential coagulation-flocculation + chemical oxidation process. J Hazard Mater. 116(1-2), 95-102.

d

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715–720.

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development during CO2 and steam activation of olive stones. Fuel Process Technol. 89,

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Sasaki, T., Lizuka, A., Watanabe, M., Hongo, T.,Yamasaki, A., 2014. Preparation and performance of arsenate (V) adsorbents derived from concrete wastes. Waste Manage. 34, 1829-1835

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Salman, J., Hameed, B., 2010. Effect of preparation conditions of oil palm fronds activated carbon on adsorption of bentazon from aqueous solutions. J. Hazard. Mater. 175, 133– 137.

ip t

Shalaby, S.C., Artok, L., Sarici, C., 2006. Preparation and characterization of activated carbons by one-step steampyrolysis/activation from apricot stones. Micropor Mesopor

cr

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adsorption by oil palm fibre activated carbon. Chem. Eng. J. 127, 111–119.

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Visvanathan, C., Tränkler., J. Zhou G., 2004. State of the Art Review: Landfill Leachate Treatment, Asian Institute of Technology, Thailand &Tongji University, China, report. 14-93. Wu, F.C., Tseng, R.L., 2008. High adsorption capacity NaOH-activated carbon for dye removal from aqueous solution. J. Hazard. Mater. 152, 1256–1267.

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Xie, Z., Guan, W., Ji, F., Song, Z., Zhao, Y., 2014. Production of Biologically Activated Carbon from Orange Peel and Landfill Leachate Subsequent Treatment Technology. J. Chem.2014, Article ID 491912, 1-9.

ip t

Yagmur, E., Ozmak, M., Aktas, Z., 2008. A novel method for production of activated carbon

cr

from waste tea by chemical activation with microwave energy. Fuel 87, 3278–3285.

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in a two-stage process: Industrial improvement. Bioresour. Technol. 99, 320-326.

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Zhang, Q.Q., Tian, B.H., Zhang, X., Ghulan, A., Fang, C.R., He, R., 2013. Investigation on characteristics of leachate and concentrated leachate in three landfill leachate treatment

te

List of Figures:

d

M

plants. Waste Manage. 33(11), 2277-2286.

Ac ce p

Figure 1: Landfill leachate formation

Figure 2: Total number of documents published, concerning landfill leachate treatment from 2000-2014 (data extracted from Scopus) Figure 3: AC consumption trend in recent decade (Figure created based on data extracted from Freedonia, 2014).

Figure 4: Per Capita consumption of AC in Kg/ Yr in different regions (Figure created based on data extracted from Freedonia, 2014).

Page 28 of 41

List of Tables: Table 1: Type of pollutants in municipal landfill Leachate Table 2: Landfill Leachate classification with respect to operational year

cr

Table 5: Optimal conditions in preparing AC using conventional heating

ip t

Table 3: Activating agents used in various activation method in the preparation of AC

Table 4: Optimal conditions in preparing AC using microwave heating

Ac ce p

te

d

M

an

us

Table 6: Landfill leachate treatment efficiency using adsorbents prepared from food waste

Page 29 of 41

Components Acids, alcohols, aldehydes and o COD, BOD, DOC (Dissolved Organic Carbon), Volatile fatty acids, refractory compound (fulvic and humic compounds)

Inorganic matters

Sulfate, chloride, ammonium, calcium, magnesium, sodium, potassium ,hydrogen, carbonate, iron, manganese, heavy metal like lead, nickel, copper, cadmium ,chromium, zinc

(Lee et al., 2010; Renou et al., 2008)

Aromatic hydrocarbon, phenols, chlorinated aliphatics, pesticides and plastizers include PCB, Dioxin, etc

(Kjeldsen et al., 2002; Foo and Hameed, 2009)

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Xenobiotic organic compounds

References (Kjeldsen et al., 2002; Lee et al., 2010)

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Group of Pollutants Organic matters

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Table 1: Type of pollutants in municipal landfill leachate

Page 30 of 41

Table 2: Landfill leachate classification with respect to operational year (Alvarez et al., 2004; Renou et al., 2008; Irene and Lo, 1996;Chian and DeWalle., 1976)

Young

Intermediate

Stabilized

Age (years)

<5

5-10

>10

pH

<6-5

6-5-7-5

>7.5

COD (mg/ L)

>10 000

4000-10 000

<4000

BOD

>10000

200-10000

50-200

BOD5/COD

0.5-1

0.1-0.5

Color

<1000

NA

TOC/COD

<0.3

0.3-0.5

>0.5

NH3-N (mg/ L)

<400

NA

Heavy metal (mg/ L)

Low to medium

Important

Kjeldahl Nitrogen (g/L)

0.1-0.2

cr

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Low

Low

5-30% (VFA)

(HA)+(FA)

Medium

Low

NA

NA

te

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biodegradability

1,500-7,000

an

80% (VFA)

<0.1

>400

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Organic compound

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Parameters

Ac ce p

Note: Not available (NA);Volatile Fatty Acid (VFA); Humic Acid (HA); Fulvic Acid (FA).

Table 3: Activating agents used in various activation methods in the preparation of AC

Page 31 of 41

Activating agent

References

Physical activation

Steam Pure steam Steam(H2SO4 Pretreatment)

(Petrov et al., 2008) (Bouchelta et al., 2008) (López de Letona Sánchez et al., 2006) (Roman et al., 2008) (Ganan et al., 2006) (Bonelli et al., 2001)

ip t

Activation method

(Nakagawa et al., 2007) (Salman and Hameed, 2010) (Tan et al., 2007)

Phosphoric Acid (H3PO4) Sulphuric acid Potassium hydroxide (KOH) Potassium Carbonate (K2CO3) Sodium hydroxide (NaOH)

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Chemical activation

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Carbon dioxide (CO2) Steam/ CO2 CO2/N2

(Foo and Hameed, 2011b)

KOH/CO2

(Din et al., 2009)

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Physicochemical activation

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(Wu et al., 2008)

Page 32 of 41

1

3 4

Material

Impregnating Chemical

Temperature (C)

Time (hr)

Impregnation Ratio (IR)

Olive stones

KOH

900

4

NA

Olive kernels

KOH

900

4

4

2159

Hazel nuts

ZnCl2

750

10

0.3

793

Peanut hulls

H3PO4

500

3

1.6

1177

Peach stones

ZnCl2

850

7

2.5

Corn cobs

KOH

850

1

4

Olive waste

Seed

KOH

800

3

Oil palm fronds

KOH

850

1

Almonds shell

H3PO4

450

1

Sugarcane baggase

ZnCl2

700

Surface Area ( m2/g)

us

cr

Aygun et al. (2003) Girgis et al. (2002)

2700

Cao et al. (2006)

1690

Skodras (2007)

3.75

2700

Salman and Hameed (2010)

0.5

1340

Bansode (2004)

3

1826

Demiral and Gunduzoglu (2010)

an

Caturla (1991)

M

d

te

Zabaniotou et al. (2008)

1000

3

1.5

Stavropoulus and Zabaniotou (2005)

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NA

Reference

et

et

et

al.

al.

al.

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2

Table 4: Optimal conditions in preparing AC using conventional heating

Table 5: Optimal conditions in preparing AC using microwave heating

33 Page 33 of 41

Material

Impregnating Chemical

Power (W)

Time (hr)

Impregnation Surface Area (IR) m2/g) 0.85 1157

350

0.5

Orange Peel

K2CO3

600

0.10

NA 1104.45

Foo and Hameed (2011)

Coconut husk

KOH

600

0.10

1.25 1356.25

Foo and Hameed (2012)

Palm shell

LiCl2

700

0.245

NA NA

Rice husk

H3PO4

700

0.5

0.75 56

Sugarcane baggase

H3PO4

700

0.5

Banana Frond

KOH

700

Olive stone

KOH

565

cr

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Yagmur et al. (2008)

us

Lim et al. (2009)

an

Kalderis et al. (2008)

Kalderis et al., 2008)

0.155

1.75 847.66

Foo and Hameed (2013a)

0.116

1.87 1280.71

Alslaibi et al. (2013b)

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0.75 173

te Ac ce p

9

(

H3PO4

6

8

Reference

Waste tea

5

7

Ratio

Table 6: Landfill leachate treatment efficiency using adsorbents prepared from food waste

Raw material

Leachate Initial Characteristics

Preparation Conditions

Treatment Conditions

Surface Area ( m2/g)

Adsorption Capacity

Removal efficiency (%)

Ref.

Banana Frond

COD 2336 mg/L, NH3-N 2550 mg/L, Boron 7.50 mg/L, Iron 9.31mg/L

Act. Time 4 min, IR. 1.75 KOH, Act. Power 600W, microwave heating

Shaking speed 120rpm

847.66

Boron, 11.09 mg/g Iron, 26.15 mg/g

Boron 97.45 %, Total Iron 95.14%

Foo et al. (2013a)

Coffee ground

COD 1478 mg/L, color 2510 Pt-Co,

Act. Temp 600 oC, IR 0.50 H2SO4,

Shaking speed 300rpm,

146.1

NA

Iron 77%, PO4-P 84%

Ching et al. (2011)

34 Page 34 of 41

contact time 150 min,

COD 3100 mg/L, color 3286 Pt-Co

Act. Temp 800 oC, Act. Time 2.1 hr, conventional heating

COD 10800 mg/L, NH3-N 2900 mg/L, pH 7.7

Commercial Palm shellAC

Shaking speed 320rpm, contact time 180 min, NA

Tamarind Fruit Seed

COD 2336, color 5095, NH3-N 2550, pH 8.2

Act. Power 600W, IR 1:1.50 KOH, Act. Time 8 min, Microwave heating

Shaking speed 120rpm

Sugarcane Baggase

COD2700, NH3-N2550, PO4-P 285mg/L

Shaking speed 120rpm

Sugarcane Baggase

COD 1,490– 1,570 mg/L, color 3,300– 3,500 Pt-Co, NH3-N 1,860– 1,950

Act. Power 600W, IR 1:1.25 KOH, Act. Time 5 min, Microwave heating Act. Temp 700 oC, IR. 2.27 KOH, Act. Time 2.0 hr, Conventional heating

Orange Peel

Rice husk carbon Composite

TOC 430mg/L

7330– 9530COD mg/L, NH3-N 685–735mg/L

NA

COD 61.72 mg/g color 100 Pt-Co/g

COD 41.98%, color 39.68%

Kamaruddin et al. (2012)

COD 1460 mg/g

COD 50%

Lim et al. (2009)

us

1620.69

M

d

color 168.57 PtCo/g, COD 64.93 mg/g

color 91.23%, COD 79.93%

Foo et al. (2013b)

NH3-N 138.46 mg/g, 12.81 PO4P mg/g

NH3-N 79.63%, PO4-P 85.06 %

Foo et al. (2013c)

an

1090.01

Shaking speed 300rpm, contact time 180 min,

NA

color 555.56 Pt/Co/g, COD 126.58 mg/g, NH3N 14.62 mg/g

color 94.74 %, COD 83.61%, NH3-N 46.65%

Azmi et al. (2015)

Act. Temp 550 oC, IR. 3 zinc chloride, Act. Time 1.0 hr, Conventional heating

Shaking speed 120rpm

1104.45 m2/g

NA

TOC 59.7%

Xie et al. (2014)

Composite adsorbent prepared from rice husk carbon waste (75 % w/w), commercial AC (8.22% w/w), and

Shaking speed 200rpm; contact time 120 min,

COD 3.11 mg/g, NH3-N 12.9 mg/g

COD 27.61%, NH3-N 51.0%

Halim et al. (2011)

Ac ce p

Palm Shell

763.31

te

Durian Peel

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Act. Time 60 min, chemical activation

cr

NH3-N 3796.75 mg/L, pH 7.5, Iron 4.57 mg/L, PO4-P 260 mg/L

NA

35 Page 35 of 41

ordinary Portland cement (16.78% w/w).

ip t

10

Ac ce p

te

d

M

an

us

cr

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ip t Figure 1: Landfill leachate formation (Visvanathan et al., 2004)

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Figure 2: Total number of documents published, concerning landfill leachate treatment from 2000-2014 (data extracted from Scopus)

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Figure 3: AC consumption trend in recent decade (Figure created based on data extracted from Freedonia, 2014)

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Figure 4: Per Capita consumption of AC in Kg/ Yr in different regions (Figure created based on data extracted from Freedonia, 2014)

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Graphical Abstract (for review)

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