- Email: [email protected]
Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design
Journal of Environmental Management xxx (2017) 1e6
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Research article
Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design Andreea Gabor, Corneliu Mircea Davidescu, Adina Negrea, Mihaela Ciopec**, Ion Grozav, Petru Negrea, Narcis Duteanu* Politehnica University of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, 2 Piata Victoriei, RO 300006 Timisoara, Romania
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 October 2016 Received in revised form 17 January 2017 Accepted 20 January 2017 Available online xxx
The rare metals' potential to pollute air, water, soil, and especially groundwater has received lot of attention recently. One of the most common rare earth group elements, lanthanum, is used in many industrial branches, and due to its toxicity, it needs to be eliminated from all residual aqueous solutions. The goal of this study was to evaluate the control of the adsorption process for lanthanum removal from aqueous solutions, using cellulose, a known biomaterial with high adsorbent properties, cheap, and environment friendly. The cellulose was chemically modified by functionalization with sodium b-glycerophosphate. The experimental results obtained after factorial design indicate optimum adsorption parameters as pH 6, contact time 60 min, and temperature 298 K, when the equilibrium concentration of lanthanum was 250 mg L1, and the experimental adsorption capacity obtained was 31.58 mg g1. Further refinement of the optimization of the adsorption process by response surface design indicates that at pH 6 and the initial concentration of 256 mg L1, the adsorption capacity has maximum values between 30.87 and 36.73 mg g1. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Adsorption Biomaterial Chemical modified cellulose Factorial design Lanthanum
1. Introduction Lanthanum is an important member of the rare earth elements (REEs), which appears in different aqueous radioactive waste streams and its effects have attracted much attention (Abdel Moamen et al., 2015; Hu et al., 2002). Pure metallic lanthanum has no commercial uses, but its alloys are used (Sui et al., 2014; Unal Yesiller et al., 2013) for superconductors, ceramics (Hirano and Suzuki, 1996) micro-fertilizer (Hu et al., 2002; Liang et al., 2005), metallurgical industry, medical application, in “flints” for cigarette lighters, studio lighting and cinema projection, or in optical glasses, while lanthanum salts are used in catalysts for petroleum refining. Lanthanum is disposed or stored in the environment in different locations. During long-term exposure, lanthanum is very dangerous, especially in the working environment, due to the gasses that can be inhaled with air. Lanthanum can also cause cancer (Hirano and Suzuki, 1996).
* Coresponding author. ** Corresponding author. E-mail addresses: [email protected] (M. Ciopec), [email protected] (N. Duteanu).
In soil and ground water, lanthanum will be gradually bioaccumulated and this will eventually lead, in time, to a concentration increase in human and animal bodies (Barry and Meehan, 2000). Lanthanum causes damage to cell membranes, which has several negative influences on reproduction and on the functions of the nervous system. It also strongly accumulates in muscles (Hirano and Suzuki, 1996). In the past, many techniques were proposed to remove lanthanum ions from wastewater with significant risks to human health and the environment, in general (Abdel Moamen et al., 2015). The most used techniques for lanthanum removal are precipitation, ion exchange and evaporation (Abdel Moamen et al., 2015; He and Loh, 2000; Hu et al., 2002). These methods differ in their efficiency and cost (Hokkanen et al., 2016). Another method for lanthanum removal is adsorption, an advanced method for treatment of wastewater with REEs, because it presents several advantages such as: high efficiency, high adsorption capacity, the possibility of regeneration and utilization in multiple adsorptions-desorption cycles, and selectivity (Dobre et al., 2014; Gabor et al., 2016; Ion et al., 2015a). There are many types of materials, natural or synthetic, all featuring economic or efficiency related advantages or disadvantages. Some of these materials, which show adsorption properties
http://dx.doi.org/10.1016/j.jenvman.2017.01.046 0301-4797/© 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
2
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
are used for lanthanum removal from aqueous solutions, are graphite activated carbon, synthetic or natural inorganic and organic polymers, composite materials, ions exchangers, etc (Ciopec et al., 2012). Cellulose is the most abundant biopolymer in nature and it has a low environmental impact. Among all the natural polymers, cellulose has good economic potential because of its abundance and its low cost. It can also be used as an adsorbent material, being an attractive alternative to synthetic adsorbents (Cortina and Warshawsky, 1997; Gabor et al., 2016; Ion et al., 2015a). Cellulose has adsorbent properties, but after surface treatment with chemical modifiers it is reported to be more effective in the removal and recovery of metals ions (Barud et al., 2008; Chen et al., 2011; Cheng et al., 2011; Dobre et al., 2014; Filho et al., 2000; Yang et al., 2014). The most used surface modifier are glycidyl methacrylate (GMA) (Hokkanen et al., 2016; Navarro et al., 1996; O'Connell et al., 2006a; O'Connell et al., 2006b, c), acrylonitrile (AN), hydroxylamine (Amidoxime) (Hokkanen et al., 2016; Kubota and Shigehisa, 1995; Kubota and Suzuki, 1995), glycidylmethacrylate (GMA)- graftedtitanium dioxide (Anirudhan et al., 2013; Hokkanen et al., 2016), N,N-methylenebis (acrylamide) (Hokkanen et al., 2016; Zheng et al., 2010), carboxyl anionic groups (Hokkanen et al., 2016; Liu et al., 2001) and acrylic acid with acrylamide (Bao-Xiu et al., 2006; Hokkanen et al., 2016). The main goal of our study was to control the adsorption process for the lanthanum removal from aqueous solution, using the factorial design and response surface methodology (Can and Yildiz, 2006; Ion et al., 2015b; Zhao et al., 2009), known for its advantages: improved process, reduced development time and overall costs (Ciopec et al., 2012; Montgomery, 2013). The novelty of our approach is the method by which the material was obtained, and the fact that the precursor used for obtaining the adsorbent is “green”, cheap and environmental friendly. The results of this study show the effect of modifying the cellulose surface with phosphate groups (sodium b-glycerophosphate) for lanthanum removal from aqueous solution, and the influence of initial pH, contact time, temperature, and initial concentrations of lanthanum on the materials adsorption capacity.
2. Materials and methods 2.1. Chemical products and instruments Cellulose microcrystalline, Avicel PH-101, supplied by SigmaAldrich, Germany, with ~50 mm particle size was used as solid support. Sodium b-glycerophosphate, Na-b-Gly-P, 99% purity, supplied by Merck, Darmstadt, Germany, was used as modifying agent. To dissolve the Na-b-Gly-P, absolute ethanol, 99.2% purity supplied by SC PAM Corporation SRL, Romania was used. To prepare the lanthanum solutions, lanthanum salt, LaCl3 7H2O, Merck, Darmstadt, Germany, was used. Distilled water was used in all experiments. The pH of solutions was measured using CRISON MultiMeter MM41 with a glass electrode, which has been calibrated using various buffer solutions. Lanthanum adsorption on the modified material was performed using a JULABO SW 23 shaker at 200 rpm. The concentration of lanthanum in aqueous phase was measured with an Inductive Coupled Plasma Atomic Mass Spectrometer (ICP-MS), using an ICPMS BRUKER aurora M90 Model. The operating conditions of the ICP-MS are presented in Table 1 from supplementary materials. The drying of the modified material was carried out in an NITECH oven at 323 K. The drying of the modified material was carried out in an NITECH oven at 323 K.
2.2. Modified cellulose preparation Modified cellulose was prepared using the dry method by placing one gram of cellulose for 24 h at ambient temperature (298 K) in ethanol containing 0,1 g of Na-b-Gly-P modifying agent. After 24 h modified cellulose was washed with deionised water and dried in a oven at 323 K for 24 h.
2.3. Lanthanum batch adsorption studies The influence of several parameters (pH, time, initial concentration, and temperature) on the lanthanum adsorption was studied in batch experiments. In order to establish the effect of the pH, samples of 0.1 g modified cellulose were mixed with 25 mL of a 50 mg L1 La (III) ion solution at several pH values (2, 4, 6 and 8). The pH value was adjusted using 0.05e2M HNO3 or 0.05e2M NaOH solutions. To study the influence of temperature and contact time on the adsorption process, the experiments were carried out using 0.1 g modified cellulose in 25 mL of a 50 mg L1 La (III) ion solution for different contact times (15, 30, 45 and 60 min) and at three different temperatures (298 K, 308 K and 318 K). Similar experiments were performed at 298 K temperature for 60 min, to study the influence of the initial concentration of La (III) ions, at different initial concentrations: 10, 50, 100, 150, 200, 250, 300, 350 and 400 mg L1. All the suspensions were stirred at 200 rpm. After stirring, the samples were filtered and the residual concentration of lanthanum was determined by inductively coupled plasma-mass spectroscopy. The adsorption capacities are defined by equation (1).
q¼
ðCi Cf Þ$V m
(1)
Where: q e adsorption capacity of modified cellulose, mg g1; Ci e initial concentration of La (III) in solution, mg L1; Cf e residual concentration of La (III) after adsorption process, mg L1; V e volume of the aqueous solutions with La (III) content, L; m e mass of the studied adsorbent, g.
2.4. Experimental design The experiment was made in two stages: Stage 1. Factorial design. The objectives of this stage are: Determining the variables which have significant influence on the adsorption process Determining where to set the controllable factors in the first stage, to obtain a maximum adsorption capacity. Stage 2. Response Surface Design. The objective of this stage was to refine the optimization process, in order to increase the maximum value for the adsorption capacity. At this stage, the setting of the important controllable factors that lead to the maximum value for adsorption capacity was determined. For both stages the software MINITAB 17.1.0 Statistical Software (2010) (Minitab, 2010) was used for planning the Factorial Design and Response Surface design.
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
3
Table 1 Response optimization from MINITAB for factorial design (Stage 1)Response Optimization Stage 1: Adsorption capacity [mg g1]. Response
Goal
Lower
Target
Upper
Weight
Importance
Ads Capac. [mg g1] Global Solution Solution 1
Maximum
1.23571
15.625
e
1
1
pH 8
Time [min] 60
Temp [C] 25
InitConc [mg L1] 250
AdsCapac. 15.625
Composite Desirability 1
3. Results and discussion 3.1. The effect of initial pH on lanthanum adsorption It is known that the pH is an essential parameter in optimizing chemical processes, in particular, for removing metal ions from aqueous solutions, as it affects the charging adsorbent surface and the degree of ionization. To determine the optimum pH range for the adsorption of La (III) ions onto modified cellulose, the pH was varied within the range 2e8, and the experimental results of these experiments are presented in Fig. 1 from supplementary materials. As was expected and also as seen from this picture, the adsorption capacity gets better with increasing the pH and the adsorption capacity reaches a plateau at pH ¼ 6, and remained constant after that. It may therefore be concluded that the optimum initial pH for the adsorption of La (III) ions onto modified cellulose is 6, when it reaches the maximum adsorption capacity of lanthanum at approximately 12 mg g1. As a consequence, this pH value was chosen for subsequent experiments in this study, also because at higher pH values lanthanum might precipitate. 3.2. The effect of temperature and contact time on lanthanum adsorption process To decide the adsorption equilibrium time, experimental results
regarding the effect of the contact time on the adsorption capacity of La (III) ions at three studied temperatures are shown in Fig. 2 from supplementary materials. It can be observed that the adsorption capacity reached the equilibrium after 60 min at all three temperatures studied. After this contact time, the increase was insignificant. The amount of La (III) ions adsorbed increased slightly when the temperature was increased from 298 K to 318 K. In conclusion, the increasing temperature has an insignificant effect on the adsorption capacity of La (III). The contact time of 60 min was selected for the following experiments. 3.3. The effect of the initial lanthanum concentration The influence of the initial lanthanum concentration on the adsorption capacity of the modified cellulose was determined by measuring the final equilibrium concentration of lanthanum ions in solution. The experimental results regarding the effect of the initial La (III) ion concentration on the adsorption capacity of La (III) ions are presented in Fig. 3 from supplementary materials. It can be seen that the adsorption capacity of La (III) grows with increasing the initial La (III) ion concentration. At higher concentrations than 250 mg L1 La (III), the adsorption capacity reached a constant value of q ¼ 31.58 mg g1, representing the maximum adsorption capacity of La (III) ions onto the modified cellulose.
Fig. 1. Interactions of the controllable factors: pH, time and initial concentration.
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
4
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
Fig. 2. Optimization plot for factorial design.
Fig. 3. Main effects for Central Composite with Face Centered (CCFC) design.
3.4. Factorial and response surface design for the adsorption process Factorial and response surface design methodology allows to study the effect of each factor on the response variable, as well as the effects of interactions between factors on the response variable. This methodology is a set of advanced design of experiments techniques that help to better understand and optimize the response variable. The response surface design methodology is often used to refine models after factorial designs have been used to determine the most important factors that influence. The vast majority of experimental designs are performed in two stages. 3.4.1. Stage 1. full factorial design In the first stage a full Factorial Design with 4 controllable factors (pH, time, temperature and initial concentration) was created, which needs a total of 16 runs (24). The results of the experiment were analyzed with MINITAB and the Pareto chart of the effects was obtained. The Pareto chart shows that only the initial concentration (D),
pH (A), and the interaction (AD) between pH and initial concentration have a significant influence upon the adsorption capacity (AdsCap). From factorial design was conclude that the pH and initial concentration have a strong positive significant influence, while time and temperature do not have a statistically significant influence upon adsorption capacity. In the following experiments we focused only on these two factors, and the interaction among controllable factors was analyzed as presented in Fig. 1. Fig. 1 highlights a significant interaction between pH and initial concentration, which is able to change the main effect of the controllable factors. The same figure shows that only the pH and the initial concentration have significant influence. From contour plot was observed that the pH and initial concentration have a nonlinear influence upon the adsorption capacity. It can be also seen that the maximum values for adsorption capacity appear at higher values of pH and initial concentration. However, although it is tempting to increase the values for pH, it is known that for pH values greater than 6 and higher concentrations the lanthanum can precipitate, interfering with the adsorption process. The optimization response from MINITAB for factorial design is presented in Table 1 and the plot of optimization in the case of factorial design is presented Fig. 2. The maximization process starts from lower value and the result of maximization is Target value (for maximization is not allocating Upper value). The weight and Importance of the response was selected equal to 1. The weight defines the shape of the desirability function for response. The optimization values for controllable factors are presented in Global Solution. The factorial design plot shows that the maximum for adsorption capacity is obtained for high values of pH, initial concentration and time. Only for temperature small values are needed. As time and temperature have a very small effect upon the adsorption capacity, for our next experiments these factors were excluded from the factorial design.
3.4.2. Stage 2. response surface design In the second stage of experiments, a response surface design for two controllable factors pH ¼ [4, 6] and initial concentration ¼ [250, 290] mg L1 La (III) was created. The chosen response surface design was one of Central Composite with Face
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
5
Table 2 ANOVA results for the central composite design. Source
Degree of freedom, df
Sum of squares
Mean Square
F-value
p-value
Model Linear pH Initial concentration [mg L1] Square pH∙pH InitConc∙ InitConc [mg L1] 2-way Interaction pH∙InitConc Error Lack-of-Fit Pure Error Total
5 2 1 1 2 1 1 1 1 8 3 5 13
120.155 44.377 42.150 2.228 19.049 0.118 14.534 56.728 56.728 23.606 21.662 1.944 143.761
24.0310 22.1887 42.1498 2.2277 9.5245 0.1177 14.5344 56.7282 56.7282 2.9508 7.2207 0.3889
8.14 7.52 14.28 0.75 3.23 0.04 4.93 19.22 19.22
0.005 0.015 0.015 0.410 0.094 0.847 0.057 0.002 0.02
18.57
0.004
Fig. 4. Interaction plot for Central Composite with Face Centered (CCFC) design.
Centered (CCFC) type. This design needs 14 runs. The analysis of variance (ANOVA) results for this CCFC design are presented in Table 2. The ANOVA results show that pH (p ¼ 0.015, p < 5%) and the initial concentration (InitConc∙*InitConc [mg L1] has p ¼ 0,057, p y 5%) have a significant influence upon adsorption capacity, that was obvious also in first stage experiment (see Fig. 5 and Fig. 6 from supplementary material). The second order interaction pH initial concentration has also a significant influence (p ¼ 0.02, p < 5%). This means that the optimum value indicated by this experiment must be verified, because the interaction can mask the main effect of the controlled factors. The main effect of the controlled factors is presented in Fig. 3. The pH factor has a linear positive effect, but the initial
concentration has a nonlinear effect, causing a maximum for adsorption capacity for its values between 270 and 275 mg L1 La (III). The interaction plot for CCFC design is presented in Fig. 4. The interaction pH - initial concentration has a variable effect. For lower values of initial concentration the interaction has a strong positive effect. For a value of initial concentration around 280 mg L1 La (III) the effect of interaction is close to zero and for values higher than 280 mg L1 La (III) the interaction effects are negative upon adsorption capacity. The adsorption capacity has a nonlinear behavior, having a maximum for pH ¼ 6 and initial concentration around a value of 270 mg L1 La (III). The optimal setting for pH and initial concentration, for a maximum value of adsorption capacity can be identified using the optimization facility, offered by MINITAB. This
Table 3 Response optimization from MINITAB for factorial design (Stage 2) Response Optimization Stage I: Ads Capac. [mg g1]. Response
Goal
Lower
Target
Upper
Weight
Importance
Ads Capac. [mg g1]
Maximum
22.8495
34.1481
e
1
1
Global Solution Solution 1 Response AdsCap [mg g1]
pH 6 Fit 33.80
InitConc [mg L1] 256.061 Standard Error Fit 1.27
AdsCapac. 33.8020 95% Confidence Interval (30.87; 36.73)
Composite Desirability 0.969367 95% Prediction Interval (28.87; 38.73)
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
6
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
optimization adsorption process response is presented in Table 3 and Fig. 5. The optimization adsorption process shows values of pH ¼ 6 and initial concentration of 256 mg L1 La (III), when the adsorption capacity has values between 30.87 mg g1 and 36.73 mg g1, having the confidence interval of 95%. Due to the interaction pH - initial concentration the optimum of adsorption capacity was verified making 10 runs with the following values for controlled factors: temperature ¼ 298 K, time ¼ 60 min, pH ¼ 6 and initial concentration ¼ 256 mg L1 La (III). The results of these ten runs are presented in Fig. 6. The distribution of the adsorption values is not normal, but the number of the runs is small. The adsorption capacity has a mean of 31 with 95% confidence interval for the means (30.35, 31.8), which is satisfactory. 4. Conclusions The present research reveals the possibility of removing lanthanum from aqueous solutions by adsorption on chemically modified cellulose by functionalization with Na-b-Gly-P, known as an environmentally friendly material and very cheap due to possible sources of cellulose. The values of experimentally determined optimum parameters are pH 6, contact time 60 min, temperature 298 K and an initial lanthanum concentration of 250 mg L1 La (III). The adsorption capacity obtained experimentally was 31.58 mg g1. The novelty of this approach is the method by which the material was obtained, and the fact that the precursor used for obtaining the adsorbent is “green”, cheap and environmental friendly. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jenvman.2017.01.046. References Abdel Moamen, O.A., Ismail, I.M., Abdelmonem, N., Abdel Rahman, R.O., 2015. Factorial design analysis for optimizing the removal of cesium and strontium ions on synthetic nano-sized zeolite. J. Taiwan Inst. Chem. Eng. 55, 133e144. Anirudhan, T.S., Nima, J., Divya, P.L., 2013. Adsorption of chromium(VI) from aqueous solutions by glycidylmethacrylate-grafted-densified cellulose with quaternary ammonium groups. Appl. Surf. Sci. 279, 441e449. Bao-Xiu, Z., Peng, W., Tong, Z., Chun-yun, C., Jing, S., 2006. Preparation and adsorption performance of a cellulosic-adsorbent resin for copper(II). J. Appl. Polym. Sci. 99, 2951e2956. Barry, M.J., Meehan, B.J., 2000. The acute and chronic toxicity of lanthanum to Daphnia carinata. Chemosphere 41, 1669e1674. Barud, H.S., de Araujo Junior, A.M., Santos, D.B., de Assuncao, R.M.N., Meireles, C.S., Cerqueira, D.A., Rodrigues Filho, G., Ribeiro, C.A., Messaddeq, Y., Ribeiro, S.J.L., 2008. Thermal behavior of cellulose acetate produced from homogeneous acetylation of bacterial cellulose. Thermochim. Acta 471, 61e69. Can, M.Y., Yildiz, E., 2006. Phosphate removal from water by fly ash: factorial experimental design. J. Hazard. Mater. 135, 165e170. Chen, X., Lam, K.F., Mak, S.F., Yeung, K.L., 2011. Precious metal recovery by selective adsorption using biosorbents. J. Hazard. Mater. 186, 902e910. Cheng, G., Varanasi, P., Li, C., Liu, H., Melnichenko, Y.B., Simmons, B.A., Kent, M.S., Singh, S., 2011. Transition of cellulose crystalline structure and surface morphology of biomass as a function of ionic liquid pretreatment and its relation to enzymatic hydrolysis. Biomacromolecules 12, 933e941. Ciopec, M., Davidescu, C.M., Negrea, A., Grozav, I., Lupa, L., Negrea, P., Popa, A., 2012.
Adsorption studies of Cr(III) ions from aqueous solutions by DEHPA impreg^V“ Factorial design analysis. Chem. Eng. Res. Des. nated onto Amberlite XAD7 a 90, 1660e1670. Cortina, J.L., Warshawsky, A., 1997. Developments in solid-liquid extraction by solvent-impregnated resins. In: Marinsky, J.A., Marcus, Y. (Eds.), Ion Exchage and Solvent Extraction. Marcel Dekker Inc., New York, pp. 195e293. Dobre, T., Parvulescu, O.C., Iavorschi, G., Stroescu, M., Stoica, A., 2014. Volatile organic compounds removal from gas streams by adsorption onto activated carbon. Ind. Eng. Chem. Res. 53, 3622e3628. Filho, G.R., da Cruz, S.F., Pasquini, D., Cerqueira, D.A., Prado, V.d.S., de Assuncao, R.M.N., 2000. Water flux through cellulose triacetate films produced from heterogeneous acetylation of sugar cane bagasse. J. Membr. Sci. 177, 225e231. Gabor, A.E., Davidescu, C.M., Negrea, A., Ciopec, M., Butnariu, M., Ianasi, C., Muntean, C., Negrea, P., 2016. Lanthanum separation from aqueous solutions using magnesium silicate functionalized with tetrabutylammonium dihydrogen phosphate. J. Chem. Eng. Data 61, 535e542. He, Y.-W., Loh, C.-S., 2000. Cerium and lanthanum promote floral initiation and reproductive growth of Arabidopsis thaliana. Plant Sci. 159, 117e124. Hirano, S., Suzuki, K.T., 1996. Exposure, metabolism, and toxicity of rare earths and related compounds. Environ. Health Perspect. 104, 85e95. Hokkanen, S., Bhatnagar, A., Sillanpaa, M., 2016. A review on modification methods to cellulose-based adsorbents to improve adsorption capacity. Water Res. 91, 156e173. Hu, X., Ding, Z., Wang, X., Chen, Y., Dai, L., 2002. Effects of lanthanum and cerium on the vegetable growth of wheat (Triticum aestivum L.) seedlings. Bull. Environ. Contam. Toxicol. 69, 0727e0733. Ion, V.A., Parvulescu, O.C., Dobre, T., 2015a. Volatile organic compounds adsorption onto neat and hybrid bacterial cellulose. Appl. Surf. Sci. 335, 137e146. Ion, V.A., Parvulescu, O.C., Dobre, T., Duteanu, N., Nitu, S.G., 2015b. Modelling of thermal desorption of volatile organic compounds from activated carbon. Rev. Chim. 66, 703e706. Kubota, H., Shigehisa, Y., 1995. Introduction of amidoxime groups into cellulose and its ability to adsorb metal ions. J. Appl. Polym. Sci. 56, 147e151. Kubota, H., Suzuki, S., 1995. Comparative examinations of reactivity of grafted celluloses prepared by u.v.- and ceric salt-initiated graftings. Eur. Polym. J. 31, 701e704. Liang, P., Liu, Y., Guo, L., 2005. Determination of trace rare earth elements by inductively coupled plasma atomic emission spectrometry after preconcentration with multiwalled carbon nanotubes. Spectrochim. Acta Part B 60, 125e129. Liu, M., Zhang, H., Zhang, X., Deng, Y., Liu, W., Zhan, H., 2001. Removal and recovery of chromium(III) from aqueous solutions by a spheroidal cellulose adsorbent. Water Environ. Res. 73, 322e328. Minitab 17 Statistical Software (2010). [Computer software]. Minitab, Inc. (www. minitab.com). Montgomery, D.C., 2013. Design and Analysis of Experiments, eighth ed. John Wiley and Sons, Inc. Navarro, R.R., Sumi, K., Fujii, N., Matsumura, M., 1996. Mercury removal from wastewater using porous cellulose carrier modified with polyethyleneimine. Water Res. 30, 2488e2494. O'Connell, D.W., Birkinshaw, C., O'Dwyer, T.F., 2006a. A chelating cellulose adsorbent for the removal of Cu(II) from aqueous solutions. J. Appl. Polym. Sci. 99, 2888e2897. O'Connell, D.W., Birkinshaw, C., O'Dwyer, T.F., 2006b. A modified cellulose adsorbent for the removal of nickel(II) from aqueous solutions. J. Chem. Technol. Biotechnol. 81, 1820e1828. O'Connell, D.W., Birkinshaw, C., O'Dwyer, T.F., 2006c. Removal of lead(II) ions from aqueous solutions using a modified cellulose adsorbent. Adsorpt. Sci. Technol. 24, 337e348. Sui, N., Huang, K., Lin, J., Li, X., Wang, X., Xiao, C., Liu, H., 2014. Removal of Al, Fe and Si from complex rare-earth leach solution: a three-liquid-phase partitioning approach. Sep. Purif. Technol. 127, 97e106. Unal Yesiller, S., Eroglu, A.E., Shahwan, T., 2013. Removal of aqueous rare earth elements (REEs) using nano-iron based materials. J. Ind. Eng. Chem. 19, 898e907. Yang, J., Kubota, F., Baba, Y., Kamiya, N., Goto, M., 2014. Application of cellulose acetate to the selective adsorption and recovery of Au(III). Carbohydr. Polym. 111, 768e774. Zhao, Y., Wang, J., Luan, Z., Peng, X., Liang, Z., Shi, L., 2009. Removal of phosphate from aqueous solution by red mud using a factorial design. J. Hazard. Mater. 165, 1193e1199. Zheng, L., Dang, Z., Yi, X., Zhang, H., 2010. Equilibrium and kinetic studies of adsorption of Cd(II) from aqueous solution using modified corn stalk. J. Hazard. Mater. 176, 650e656.
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Research article
Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design Andreea Gabor, Corneliu Mircea Davidescu, Adina Negrea, Mihaela Ciopec**, Ion Grozav, Petru Negrea, Narcis Duteanu* Politehnica University of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, 2 Piata Victoriei, RO 300006 Timisoara, Romania
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 October 2016 Received in revised form 17 January 2017 Accepted 20 January 2017 Available online xxx
The rare metals' potential to pollute air, water, soil, and especially groundwater has received lot of attention recently. One of the most common rare earth group elements, lanthanum, is used in many industrial branches, and due to its toxicity, it needs to be eliminated from all residual aqueous solutions. The goal of this study was to evaluate the control of the adsorption process for lanthanum removal from aqueous solutions, using cellulose, a known biomaterial with high adsorbent properties, cheap, and environment friendly. The cellulose was chemically modified by functionalization with sodium b-glycerophosphate. The experimental results obtained after factorial design indicate optimum adsorption parameters as pH 6, contact time 60 min, and temperature 298 K, when the equilibrium concentration of lanthanum was 250 mg L1, and the experimental adsorption capacity obtained was 31.58 mg g1. Further refinement of the optimization of the adsorption process by response surface design indicates that at pH 6 and the initial concentration of 256 mg L1, the adsorption capacity has maximum values between 30.87 and 36.73 mg g1. © 2017 Elsevier Ltd. All rights reserved.
Keywords: Adsorption Biomaterial Chemical modified cellulose Factorial design Lanthanum
1. Introduction Lanthanum is an important member of the rare earth elements (REEs), which appears in different aqueous radioactive waste streams and its effects have attracted much attention (Abdel Moamen et al., 2015; Hu et al., 2002). Pure metallic lanthanum has no commercial uses, but its alloys are used (Sui et al., 2014; Unal Yesiller et al., 2013) for superconductors, ceramics (Hirano and Suzuki, 1996) micro-fertilizer (Hu et al., 2002; Liang et al., 2005), metallurgical industry, medical application, in “flints” for cigarette lighters, studio lighting and cinema projection, or in optical glasses, while lanthanum salts are used in catalysts for petroleum refining. Lanthanum is disposed or stored in the environment in different locations. During long-term exposure, lanthanum is very dangerous, especially in the working environment, due to the gasses that can be inhaled with air. Lanthanum can also cause cancer (Hirano and Suzuki, 1996).
* Coresponding author. ** Corresponding author. E-mail addresses: [email protected] (M. Ciopec), [email protected] (N. Duteanu).
In soil and ground water, lanthanum will be gradually bioaccumulated and this will eventually lead, in time, to a concentration increase in human and animal bodies (Barry and Meehan, 2000). Lanthanum causes damage to cell membranes, which has several negative influences on reproduction and on the functions of the nervous system. It also strongly accumulates in muscles (Hirano and Suzuki, 1996). In the past, many techniques were proposed to remove lanthanum ions from wastewater with significant risks to human health and the environment, in general (Abdel Moamen et al., 2015). The most used techniques for lanthanum removal are precipitation, ion exchange and evaporation (Abdel Moamen et al., 2015; He and Loh, 2000; Hu et al., 2002). These methods differ in their efficiency and cost (Hokkanen et al., 2016). Another method for lanthanum removal is adsorption, an advanced method for treatment of wastewater with REEs, because it presents several advantages such as: high efficiency, high adsorption capacity, the possibility of regeneration and utilization in multiple adsorptions-desorption cycles, and selectivity (Dobre et al., 2014; Gabor et al., 2016; Ion et al., 2015a). There are many types of materials, natural or synthetic, all featuring economic or efficiency related advantages or disadvantages. Some of these materials, which show adsorption properties
http://dx.doi.org/10.1016/j.jenvman.2017.01.046 0301-4797/© 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
2
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
are used for lanthanum removal from aqueous solutions, are graphite activated carbon, synthetic or natural inorganic and organic polymers, composite materials, ions exchangers, etc (Ciopec et al., 2012). Cellulose is the most abundant biopolymer in nature and it has a low environmental impact. Among all the natural polymers, cellulose has good economic potential because of its abundance and its low cost. It can also be used as an adsorbent material, being an attractive alternative to synthetic adsorbents (Cortina and Warshawsky, 1997; Gabor et al., 2016; Ion et al., 2015a). Cellulose has adsorbent properties, but after surface treatment with chemical modifiers it is reported to be more effective in the removal and recovery of metals ions (Barud et al., 2008; Chen et al., 2011; Cheng et al., 2011; Dobre et al., 2014; Filho et al., 2000; Yang et al., 2014). The most used surface modifier are glycidyl methacrylate (GMA) (Hokkanen et al., 2016; Navarro et al., 1996; O'Connell et al., 2006a; O'Connell et al., 2006b, c), acrylonitrile (AN), hydroxylamine (Amidoxime) (Hokkanen et al., 2016; Kubota and Shigehisa, 1995; Kubota and Suzuki, 1995), glycidylmethacrylate (GMA)- graftedtitanium dioxide (Anirudhan et al., 2013; Hokkanen et al., 2016), N,N-methylenebis (acrylamide) (Hokkanen et al., 2016; Zheng et al., 2010), carboxyl anionic groups (Hokkanen et al., 2016; Liu et al., 2001) and acrylic acid with acrylamide (Bao-Xiu et al., 2006; Hokkanen et al., 2016). The main goal of our study was to control the adsorption process for the lanthanum removal from aqueous solution, using the factorial design and response surface methodology (Can and Yildiz, 2006; Ion et al., 2015b; Zhao et al., 2009), known for its advantages: improved process, reduced development time and overall costs (Ciopec et al., 2012; Montgomery, 2013). The novelty of our approach is the method by which the material was obtained, and the fact that the precursor used for obtaining the adsorbent is “green”, cheap and environmental friendly. The results of this study show the effect of modifying the cellulose surface with phosphate groups (sodium b-glycerophosphate) for lanthanum removal from aqueous solution, and the influence of initial pH, contact time, temperature, and initial concentrations of lanthanum on the materials adsorption capacity.
2. Materials and methods 2.1. Chemical products and instruments Cellulose microcrystalline, Avicel PH-101, supplied by SigmaAldrich, Germany, with ~50 mm particle size was used as solid support. Sodium b-glycerophosphate, Na-b-Gly-P, 99% purity, supplied by Merck, Darmstadt, Germany, was used as modifying agent. To dissolve the Na-b-Gly-P, absolute ethanol, 99.2% purity supplied by SC PAM Corporation SRL, Romania was used. To prepare the lanthanum solutions, lanthanum salt, LaCl3 7H2O, Merck, Darmstadt, Germany, was used. Distilled water was used in all experiments. The pH of solutions was measured using CRISON MultiMeter MM41 with a glass electrode, which has been calibrated using various buffer solutions. Lanthanum adsorption on the modified material was performed using a JULABO SW 23 shaker at 200 rpm. The concentration of lanthanum in aqueous phase was measured with an Inductive Coupled Plasma Atomic Mass Spectrometer (ICP-MS), using an ICPMS BRUKER aurora M90 Model. The operating conditions of the ICP-MS are presented in Table 1 from supplementary materials. The drying of the modified material was carried out in an NITECH oven at 323 K. The drying of the modified material was carried out in an NITECH oven at 323 K.
2.2. Modified cellulose preparation Modified cellulose was prepared using the dry method by placing one gram of cellulose for 24 h at ambient temperature (298 K) in ethanol containing 0,1 g of Na-b-Gly-P modifying agent. After 24 h modified cellulose was washed with deionised water and dried in a oven at 323 K for 24 h.
2.3. Lanthanum batch adsorption studies The influence of several parameters (pH, time, initial concentration, and temperature) on the lanthanum adsorption was studied in batch experiments. In order to establish the effect of the pH, samples of 0.1 g modified cellulose were mixed with 25 mL of a 50 mg L1 La (III) ion solution at several pH values (2, 4, 6 and 8). The pH value was adjusted using 0.05e2M HNO3 or 0.05e2M NaOH solutions. To study the influence of temperature and contact time on the adsorption process, the experiments were carried out using 0.1 g modified cellulose in 25 mL of a 50 mg L1 La (III) ion solution for different contact times (15, 30, 45 and 60 min) and at three different temperatures (298 K, 308 K and 318 K). Similar experiments were performed at 298 K temperature for 60 min, to study the influence of the initial concentration of La (III) ions, at different initial concentrations: 10, 50, 100, 150, 200, 250, 300, 350 and 400 mg L1. All the suspensions were stirred at 200 rpm. After stirring, the samples were filtered and the residual concentration of lanthanum was determined by inductively coupled plasma-mass spectroscopy. The adsorption capacities are defined by equation (1).
q¼
ðCi Cf Þ$V m
(1)
Where: q e adsorption capacity of modified cellulose, mg g1; Ci e initial concentration of La (III) in solution, mg L1; Cf e residual concentration of La (III) after adsorption process, mg L1; V e volume of the aqueous solutions with La (III) content, L; m e mass of the studied adsorbent, g.
2.4. Experimental design The experiment was made in two stages: Stage 1. Factorial design. The objectives of this stage are: Determining the variables which have significant influence on the adsorption process Determining where to set the controllable factors in the first stage, to obtain a maximum adsorption capacity. Stage 2. Response Surface Design. The objective of this stage was to refine the optimization process, in order to increase the maximum value for the adsorption capacity. At this stage, the setting of the important controllable factors that lead to the maximum value for adsorption capacity was determined. For both stages the software MINITAB 17.1.0 Statistical Software (2010) (Minitab, 2010) was used for planning the Factorial Design and Response Surface design.
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
3
Table 1 Response optimization from MINITAB for factorial design (Stage 1)Response Optimization Stage 1: Adsorption capacity [mg g1]. Response
Goal
Lower
Target
Upper
Weight
Importance
Ads Capac. [mg g1] Global Solution Solution 1
Maximum
1.23571
15.625
e
1
1
pH 8
Time [min] 60
Temp [C] 25
InitConc [mg L1] 250
AdsCapac. 15.625
Composite Desirability 1
3. Results and discussion 3.1. The effect of initial pH on lanthanum adsorption It is known that the pH is an essential parameter in optimizing chemical processes, in particular, for removing metal ions from aqueous solutions, as it affects the charging adsorbent surface and the degree of ionization. To determine the optimum pH range for the adsorption of La (III) ions onto modified cellulose, the pH was varied within the range 2e8, and the experimental results of these experiments are presented in Fig. 1 from supplementary materials. As was expected and also as seen from this picture, the adsorption capacity gets better with increasing the pH and the adsorption capacity reaches a plateau at pH ¼ 6, and remained constant after that. It may therefore be concluded that the optimum initial pH for the adsorption of La (III) ions onto modified cellulose is 6, when it reaches the maximum adsorption capacity of lanthanum at approximately 12 mg g1. As a consequence, this pH value was chosen for subsequent experiments in this study, also because at higher pH values lanthanum might precipitate. 3.2. The effect of temperature and contact time on lanthanum adsorption process To decide the adsorption equilibrium time, experimental results
regarding the effect of the contact time on the adsorption capacity of La (III) ions at three studied temperatures are shown in Fig. 2 from supplementary materials. It can be observed that the adsorption capacity reached the equilibrium after 60 min at all three temperatures studied. After this contact time, the increase was insignificant. The amount of La (III) ions adsorbed increased slightly when the temperature was increased from 298 K to 318 K. In conclusion, the increasing temperature has an insignificant effect on the adsorption capacity of La (III). The contact time of 60 min was selected for the following experiments. 3.3. The effect of the initial lanthanum concentration The influence of the initial lanthanum concentration on the adsorption capacity of the modified cellulose was determined by measuring the final equilibrium concentration of lanthanum ions in solution. The experimental results regarding the effect of the initial La (III) ion concentration on the adsorption capacity of La (III) ions are presented in Fig. 3 from supplementary materials. It can be seen that the adsorption capacity of La (III) grows with increasing the initial La (III) ion concentration. At higher concentrations than 250 mg L1 La (III), the adsorption capacity reached a constant value of q ¼ 31.58 mg g1, representing the maximum adsorption capacity of La (III) ions onto the modified cellulose.
Fig. 1. Interactions of the controllable factors: pH, time and initial concentration.
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
4
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
Fig. 2. Optimization plot for factorial design.
Fig. 3. Main effects for Central Composite with Face Centered (CCFC) design.
3.4. Factorial and response surface design for the adsorption process Factorial and response surface design methodology allows to study the effect of each factor on the response variable, as well as the effects of interactions between factors on the response variable. This methodology is a set of advanced design of experiments techniques that help to better understand and optimize the response variable. The response surface design methodology is often used to refine models after factorial designs have been used to determine the most important factors that influence. The vast majority of experimental designs are performed in two stages. 3.4.1. Stage 1. full factorial design In the first stage a full Factorial Design with 4 controllable factors (pH, time, temperature and initial concentration) was created, which needs a total of 16 runs (24). The results of the experiment were analyzed with MINITAB and the Pareto chart of the effects was obtained. The Pareto chart shows that only the initial concentration (D),
pH (A), and the interaction (AD) between pH and initial concentration have a significant influence upon the adsorption capacity (AdsCap). From factorial design was conclude that the pH and initial concentration have a strong positive significant influence, while time and temperature do not have a statistically significant influence upon adsorption capacity. In the following experiments we focused only on these two factors, and the interaction among controllable factors was analyzed as presented in Fig. 1. Fig. 1 highlights a significant interaction between pH and initial concentration, which is able to change the main effect of the controllable factors. The same figure shows that only the pH and the initial concentration have significant influence. From contour plot was observed that the pH and initial concentration have a nonlinear influence upon the adsorption capacity. It can be also seen that the maximum values for adsorption capacity appear at higher values of pH and initial concentration. However, although it is tempting to increase the values for pH, it is known that for pH values greater than 6 and higher concentrations the lanthanum can precipitate, interfering with the adsorption process. The optimization response from MINITAB for factorial design is presented in Table 1 and the plot of optimization in the case of factorial design is presented Fig. 2. The maximization process starts from lower value and the result of maximization is Target value (for maximization is not allocating Upper value). The weight and Importance of the response was selected equal to 1. The weight defines the shape of the desirability function for response. The optimization values for controllable factors are presented in Global Solution. The factorial design plot shows that the maximum for adsorption capacity is obtained for high values of pH, initial concentration and time. Only for temperature small values are needed. As time and temperature have a very small effect upon the adsorption capacity, for our next experiments these factors were excluded from the factorial design.
3.4.2. Stage 2. response surface design In the second stage of experiments, a response surface design for two controllable factors pH ¼ [4, 6] and initial concentration ¼ [250, 290] mg L1 La (III) was created. The chosen response surface design was one of Central Composite with Face
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
5
Table 2 ANOVA results for the central composite design. Source
Degree of freedom, df
Sum of squares
Mean Square
F-value
p-value
Model Linear pH Initial concentration [mg L1] Square pH∙pH InitConc∙ InitConc [mg L1] 2-way Interaction pH∙InitConc Error Lack-of-Fit Pure Error Total
5 2 1 1 2 1 1 1 1 8 3 5 13
120.155 44.377 42.150 2.228 19.049 0.118 14.534 56.728 56.728 23.606 21.662 1.944 143.761
24.0310 22.1887 42.1498 2.2277 9.5245 0.1177 14.5344 56.7282 56.7282 2.9508 7.2207 0.3889
8.14 7.52 14.28 0.75 3.23 0.04 4.93 19.22 19.22
0.005 0.015 0.015 0.410 0.094 0.847 0.057 0.002 0.02
18.57
0.004
Fig. 4. Interaction plot for Central Composite with Face Centered (CCFC) design.
Centered (CCFC) type. This design needs 14 runs. The analysis of variance (ANOVA) results for this CCFC design are presented in Table 2. The ANOVA results show that pH (p ¼ 0.015, p < 5%) and the initial concentration (InitConc∙*InitConc [mg L1] has p ¼ 0,057, p y 5%) have a significant influence upon adsorption capacity, that was obvious also in first stage experiment (see Fig. 5 and Fig. 6 from supplementary material). The second order interaction pH initial concentration has also a significant influence (p ¼ 0.02, p < 5%). This means that the optimum value indicated by this experiment must be verified, because the interaction can mask the main effect of the controlled factors. The main effect of the controlled factors is presented in Fig. 3. The pH factor has a linear positive effect, but the initial
concentration has a nonlinear effect, causing a maximum for adsorption capacity for its values between 270 and 275 mg L1 La (III). The interaction plot for CCFC design is presented in Fig. 4. The interaction pH - initial concentration has a variable effect. For lower values of initial concentration the interaction has a strong positive effect. For a value of initial concentration around 280 mg L1 La (III) the effect of interaction is close to zero and for values higher than 280 mg L1 La (III) the interaction effects are negative upon adsorption capacity. The adsorption capacity has a nonlinear behavior, having a maximum for pH ¼ 6 and initial concentration around a value of 270 mg L1 La (III). The optimal setting for pH and initial concentration, for a maximum value of adsorption capacity can be identified using the optimization facility, offered by MINITAB. This
Table 3 Response optimization from MINITAB for factorial design (Stage 2) Response Optimization Stage I: Ads Capac. [mg g1]. Response
Goal
Lower
Target
Upper
Weight
Importance
Ads Capac. [mg g1]
Maximum
22.8495
34.1481
e
1
1
Global Solution Solution 1 Response AdsCap [mg g1]
pH 6 Fit 33.80
InitConc [mg L1] 256.061 Standard Error Fit 1.27
AdsCapac. 33.8020 95% Confidence Interval (30.87; 36.73)
Composite Desirability 0.969367 95% Prediction Interval (28.87; 38.73)
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046
6
A. Gabor et al. / Journal of Environmental Management xxx (2017) 1e6
optimization adsorption process response is presented in Table 3 and Fig. 5. The optimization adsorption process shows values of pH ¼ 6 and initial concentration of 256 mg L1 La (III), when the adsorption capacity has values between 30.87 mg g1 and 36.73 mg g1, having the confidence interval of 95%. Due to the interaction pH - initial concentration the optimum of adsorption capacity was verified making 10 runs with the following values for controlled factors: temperature ¼ 298 K, time ¼ 60 min, pH ¼ 6 and initial concentration ¼ 256 mg L1 La (III). The results of these ten runs are presented in Fig. 6. The distribution of the adsorption values is not normal, but the number of the runs is small. The adsorption capacity has a mean of 31 with 95% confidence interval for the means (30.35, 31.8), which is satisfactory. 4. Conclusions The present research reveals the possibility of removing lanthanum from aqueous solutions by adsorption on chemically modified cellulose by functionalization with Na-b-Gly-P, known as an environmentally friendly material and very cheap due to possible sources of cellulose. The values of experimentally determined optimum parameters are pH 6, contact time 60 min, temperature 298 K and an initial lanthanum concentration of 250 mg L1 La (III). The adsorption capacity obtained experimentally was 31.58 mg g1. The novelty of this approach is the method by which the material was obtained, and the fact that the precursor used for obtaining the adsorbent is “green”, cheap and environmental friendly. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jenvman.2017.01.046. References Abdel Moamen, O.A., Ismail, I.M., Abdelmonem, N., Abdel Rahman, R.O., 2015. Factorial design analysis for optimizing the removal of cesium and strontium ions on synthetic nano-sized zeolite. J. Taiwan Inst. Chem. Eng. 55, 133e144. Anirudhan, T.S., Nima, J., Divya, P.L., 2013. Adsorption of chromium(VI) from aqueous solutions by glycidylmethacrylate-grafted-densified cellulose with quaternary ammonium groups. Appl. Surf. Sci. 279, 441e449. Bao-Xiu, Z., Peng, W., Tong, Z., Chun-yun, C., Jing, S., 2006. Preparation and adsorption performance of a cellulosic-adsorbent resin for copper(II). J. Appl. Polym. Sci. 99, 2951e2956. Barry, M.J., Meehan, B.J., 2000. The acute and chronic toxicity of lanthanum to Daphnia carinata. Chemosphere 41, 1669e1674. Barud, H.S., de Araujo Junior, A.M., Santos, D.B., de Assuncao, R.M.N., Meireles, C.S., Cerqueira, D.A., Rodrigues Filho, G., Ribeiro, C.A., Messaddeq, Y., Ribeiro, S.J.L., 2008. Thermal behavior of cellulose acetate produced from homogeneous acetylation of bacterial cellulose. Thermochim. Acta 471, 61e69. Can, M.Y., Yildiz, E., 2006. Phosphate removal from water by fly ash: factorial experimental design. J. Hazard. Mater. 135, 165e170. Chen, X., Lam, K.F., Mak, S.F., Yeung, K.L., 2011. Precious metal recovery by selective adsorption using biosorbents. J. Hazard. Mater. 186, 902e910. Cheng, G., Varanasi, P., Li, C., Liu, H., Melnichenko, Y.B., Simmons, B.A., Kent, M.S., Singh, S., 2011. Transition of cellulose crystalline structure and surface morphology of biomass as a function of ionic liquid pretreatment and its relation to enzymatic hydrolysis. Biomacromolecules 12, 933e941. Ciopec, M., Davidescu, C.M., Negrea, A., Grozav, I., Lupa, L., Negrea, P., Popa, A., 2012.
Adsorption studies of Cr(III) ions from aqueous solutions by DEHPA impreg^V“ Factorial design analysis. Chem. Eng. Res. Des. nated onto Amberlite XAD7 a 90, 1660e1670. Cortina, J.L., Warshawsky, A., 1997. Developments in solid-liquid extraction by solvent-impregnated resins. In: Marinsky, J.A., Marcus, Y. (Eds.), Ion Exchage and Solvent Extraction. Marcel Dekker Inc., New York, pp. 195e293. Dobre, T., Parvulescu, O.C., Iavorschi, G., Stroescu, M., Stoica, A., 2014. Volatile organic compounds removal from gas streams by adsorption onto activated carbon. Ind. Eng. Chem. Res. 53, 3622e3628. Filho, G.R., da Cruz, S.F., Pasquini, D., Cerqueira, D.A., Prado, V.d.S., de Assuncao, R.M.N., 2000. Water flux through cellulose triacetate films produced from heterogeneous acetylation of sugar cane bagasse. J. Membr. Sci. 177, 225e231. Gabor, A.E., Davidescu, C.M., Negrea, A., Ciopec, M., Butnariu, M., Ianasi, C., Muntean, C., Negrea, P., 2016. Lanthanum separation from aqueous solutions using magnesium silicate functionalized with tetrabutylammonium dihydrogen phosphate. J. Chem. Eng. Data 61, 535e542. He, Y.-W., Loh, C.-S., 2000. Cerium and lanthanum promote floral initiation and reproductive growth of Arabidopsis thaliana. Plant Sci. 159, 117e124. Hirano, S., Suzuki, K.T., 1996. Exposure, metabolism, and toxicity of rare earths and related compounds. Environ. Health Perspect. 104, 85e95. Hokkanen, S., Bhatnagar, A., Sillanpaa, M., 2016. A review on modification methods to cellulose-based adsorbents to improve adsorption capacity. Water Res. 91, 156e173. Hu, X., Ding, Z., Wang, X., Chen, Y., Dai, L., 2002. Effects of lanthanum and cerium on the vegetable growth of wheat (Triticum aestivum L.) seedlings. Bull. Environ. Contam. Toxicol. 69, 0727e0733. Ion, V.A., Parvulescu, O.C., Dobre, T., 2015a. Volatile organic compounds adsorption onto neat and hybrid bacterial cellulose. Appl. Surf. Sci. 335, 137e146. Ion, V.A., Parvulescu, O.C., Dobre, T., Duteanu, N., Nitu, S.G., 2015b. Modelling of thermal desorption of volatile organic compounds from activated carbon. Rev. Chim. 66, 703e706. Kubota, H., Shigehisa, Y., 1995. Introduction of amidoxime groups into cellulose and its ability to adsorb metal ions. J. Appl. Polym. Sci. 56, 147e151. Kubota, H., Suzuki, S., 1995. Comparative examinations of reactivity of grafted celluloses prepared by u.v.- and ceric salt-initiated graftings. Eur. Polym. J. 31, 701e704. Liang, P., Liu, Y., Guo, L., 2005. Determination of trace rare earth elements by inductively coupled plasma atomic emission spectrometry after preconcentration with multiwalled carbon nanotubes. Spectrochim. Acta Part B 60, 125e129. Liu, M., Zhang, H., Zhang, X., Deng, Y., Liu, W., Zhan, H., 2001. Removal and recovery of chromium(III) from aqueous solutions by a spheroidal cellulose adsorbent. Water Environ. Res. 73, 322e328. Minitab 17 Statistical Software (2010). [Computer software]. Minitab, Inc. (www. minitab.com). Montgomery, D.C., 2013. Design and Analysis of Experiments, eighth ed. John Wiley and Sons, Inc. Navarro, R.R., Sumi, K., Fujii, N., Matsumura, M., 1996. Mercury removal from wastewater using porous cellulose carrier modified with polyethyleneimine. Water Res. 30, 2488e2494. O'Connell, D.W., Birkinshaw, C., O'Dwyer, T.F., 2006a. A chelating cellulose adsorbent for the removal of Cu(II) from aqueous solutions. J. Appl. Polym. Sci. 99, 2888e2897. O'Connell, D.W., Birkinshaw, C., O'Dwyer, T.F., 2006b. A modified cellulose adsorbent for the removal of nickel(II) from aqueous solutions. J. Chem. Technol. Biotechnol. 81, 1820e1828. O'Connell, D.W., Birkinshaw, C., O'Dwyer, T.F., 2006c. Removal of lead(II) ions from aqueous solutions using a modified cellulose adsorbent. Adsorpt. Sci. Technol. 24, 337e348. Sui, N., Huang, K., Lin, J., Li, X., Wang, X., Xiao, C., Liu, H., 2014. Removal of Al, Fe and Si from complex rare-earth leach solution: a three-liquid-phase partitioning approach. Sep. Purif. Technol. 127, 97e106. Unal Yesiller, S., Eroglu, A.E., Shahwan, T., 2013. Removal of aqueous rare earth elements (REEs) using nano-iron based materials. J. Ind. Eng. Chem. 19, 898e907. Yang, J., Kubota, F., Baba, Y., Kamiya, N., Goto, M., 2014. Application of cellulose acetate to the selective adsorption and recovery of Au(III). Carbohydr. Polym. 111, 768e774. Zhao, Y., Wang, J., Luan, Z., Peng, X., Liang, Z., Shi, L., 2009. Removal of phosphate from aqueous solution by red mud using a factorial design. J. Hazard. Mater. 165, 1193e1199. Zheng, L., Dang, Z., Yi, X., Zhang, H., 2010. Equilibrium and kinetic studies of adsorption of Cd(II) from aqueous solution using modified corn stalk. J. Hazard. Mater. 176, 650e656.
Please cite this article in press as: Gabor, A., et al., Optimizing the lanthanum adsorption process onto chemically modified biomaterials using factorial and response surface design, Journal of Environmental Management (2017), http://dx.doi.org/10.1016/j.jenvman.2017.01.046