- Email: [email protected]
Photocatalysis
Solar Energy 77 (2004) 443–444 www.elsevier.com/locate/solener
Guest editorial
Photocatalysis
Human health is threatened by high concentrations of pesticides, heavy metals, hydrocarbons, chlorinated hydrocarbons, etc., present in the environment, usually dissolved in water as a result of low-to-medium contaminant concentrations (<500 mg/l) in industrial effluents. The treatment of such wastewater is based on various mechanical, biological, physical and chemical processes. After filtration and elimination of particles in suspension, biological treatment is ideal. Unfortunately, there are certain products, called bio-recalcitrant (non-biodegradable), for which much more effective reactive systems, such as air stripping, adsorption on granulated activated carbon, incineration, ozone and oxidation are required. The strong potential of Advanced Oxidation Processes (AOPs) for bio-recalcitrant wastewater treatment is universally recognized today and many researchers around the world are devoting their efforts to the development of these processes. Although they make use of different reaction systems, AOPs are all characterised by the same chemical feature, the production of OH radicals (OH). A useful attribute in pollution problems is that the attack selectivity of these radicals is very low. But, it is also well known that AOP operating costs for the total oxidation of hazardous organic compounds remain relatively high. Two catalytic AOP systems (TiO2 and photo-Fenton) are of special interest because they can be performed using sunlight, making the development of suitable technologies very attractive for practical applications. Solar energy technologies for water recycling applications is an important field of development in which the sun, as a versatile non-polluting energy source, can provide a significant environmental added value for sustainable water and hazardous waste management strategies. It has been shown that investment in these clean, energysaving technologies for wastewater treatment and nature conservation could contribute to higher employment rates, both through increased competitiveness of compa-
nies and an increasing demand for environmentally friendly products and services. Their future implementation could also provide additional job opportunities in underdeveloped regions, leading to more balanced social conditions. Cross contamination of water supply by hazardous chemical substances and microbiological pollutants is also an important problem with serious potential implications for human health, especially in many areas of developing countries (DC). Water disinfection is recognized by the WHO as one of the most important challenges for human health protection. Standard water treatment techniques are often too expensive, because of the high capital investment, operating and maintenance costs, to be used in DC. The use of solar energy as a primary alternative to chlorination and other conventional water treatment techniques could prove feasible in those countries where there is also abundant sunlight. Solar photocatalytic oxidation treatment could also be an efficient way to degrade organic matter in water, making it apt for human consumption, and a most promising technology for both disinfection and wastewater treatment in these countries. The main purpose of this Special Issue is to collect the most relevant efforts on the subject currently underway by leading research groups. The work presented here is an excellent review of state-of-the-art solar photocatalytic water treatment, presented in 21 papers from Argentina, Austria, Brazil, Canada, France, Germany, Greece, Ireland, Mexico, Japan, Poland, Portugal, Spain and Switzerland, covering solar wastewater treatment by TiO2 and by photo-Fenton in real applications (pesticides, surfactants, dyes, olive-mill wastewater, etc.), solar photocatalytic disinfection of E. coli, solar photocatalytic collector modelling, comparison and design, and use of immobilised photosensitizers. The quality and scope of these papers shows that the potential for commercially viable, economical processes
0038-092X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.solener.2004.09.001
444
Guest editorial / Solar Energy 77 (2004) 443–444
and applications is very high, clearly indicating that Solar Photocatalysis is at an advanced stage of development. We hope this publication will help to stimulate further research towards the goal of cost-effective solar detoxification and disinfection technologies. The future of the technology is very exciting, because there are many specific applications still awaiting practical solutions, especially in DC, where the need is acute, but where, fortunately, the sun shines brightly every day! The invited editors particularly appreciate the financial support of the ‘‘SOLWATER Project’’, (Contract No. ICA4-CT-2002-10001, http://www.psa.es/webeng/ solwater) and the ‘‘CADOX Project’’ (Contract No. EVK1-CT-2002-00122, http://www.psa.es/webeng/projects/cadox/index.html) for its financial assistance during the preparation of this Special Issue.
Sixto Malato Rodrı´guez Julia´n Blanco Ga´lvez Plataforma Solar de Almerı´a—CIEMAT Ctra. Sene´s Km. 4, Tabernas Almerı´a 04200, Spain Tel.: +34 950 387 940; fax: +34 950365015 E-mail addresses: [email protected] [email protected] Claudio A. Estrada Gasca Centro de Investigacio´n en Energı´a Universidad Nacional Auto´noma de Me´xico AP 34 Temixco Morelos 62580, Me´xico E-mail address: [email protected] Available online 11 September 2004
Guest editorial
Photocatalysis
Human health is threatened by high concentrations of pesticides, heavy metals, hydrocarbons, chlorinated hydrocarbons, etc., present in the environment, usually dissolved in water as a result of low-to-medium contaminant concentrations (<500 mg/l) in industrial effluents. The treatment of such wastewater is based on various mechanical, biological, physical and chemical processes. After filtration and elimination of particles in suspension, biological treatment is ideal. Unfortunately, there are certain products, called bio-recalcitrant (non-biodegradable), for which much more effective reactive systems, such as air stripping, adsorption on granulated activated carbon, incineration, ozone and oxidation are required. The strong potential of Advanced Oxidation Processes (AOPs) for bio-recalcitrant wastewater treatment is universally recognized today and many researchers around the world are devoting their efforts to the development of these processes. Although they make use of different reaction systems, AOPs are all characterised by the same chemical feature, the production of OH radicals (OH). A useful attribute in pollution problems is that the attack selectivity of these radicals is very low. But, it is also well known that AOP operating costs for the total oxidation of hazardous organic compounds remain relatively high. Two catalytic AOP systems (TiO2 and photo-Fenton) are of special interest because they can be performed using sunlight, making the development of suitable technologies very attractive for practical applications. Solar energy technologies for water recycling applications is an important field of development in which the sun, as a versatile non-polluting energy source, can provide a significant environmental added value for sustainable water and hazardous waste management strategies. It has been shown that investment in these clean, energysaving technologies for wastewater treatment and nature conservation could contribute to higher employment rates, both through increased competitiveness of compa-
nies and an increasing demand for environmentally friendly products and services. Their future implementation could also provide additional job opportunities in underdeveloped regions, leading to more balanced social conditions. Cross contamination of water supply by hazardous chemical substances and microbiological pollutants is also an important problem with serious potential implications for human health, especially in many areas of developing countries (DC). Water disinfection is recognized by the WHO as one of the most important challenges for human health protection. Standard water treatment techniques are often too expensive, because of the high capital investment, operating and maintenance costs, to be used in DC. The use of solar energy as a primary alternative to chlorination and other conventional water treatment techniques could prove feasible in those countries where there is also abundant sunlight. Solar photocatalytic oxidation treatment could also be an efficient way to degrade organic matter in water, making it apt for human consumption, and a most promising technology for both disinfection and wastewater treatment in these countries. The main purpose of this Special Issue is to collect the most relevant efforts on the subject currently underway by leading research groups. The work presented here is an excellent review of state-of-the-art solar photocatalytic water treatment, presented in 21 papers from Argentina, Austria, Brazil, Canada, France, Germany, Greece, Ireland, Mexico, Japan, Poland, Portugal, Spain and Switzerland, covering solar wastewater treatment by TiO2 and by photo-Fenton in real applications (pesticides, surfactants, dyes, olive-mill wastewater, etc.), solar photocatalytic disinfection of E. coli, solar photocatalytic collector modelling, comparison and design, and use of immobilised photosensitizers. The quality and scope of these papers shows that the potential for commercially viable, economical processes
0038-092X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.solener.2004.09.001
444
Guest editorial / Solar Energy 77 (2004) 443–444
and applications is very high, clearly indicating that Solar Photocatalysis is at an advanced stage of development. We hope this publication will help to stimulate further research towards the goal of cost-effective solar detoxification and disinfection technologies. The future of the technology is very exciting, because there are many specific applications still awaiting practical solutions, especially in DC, where the need is acute, but where, fortunately, the sun shines brightly every day! The invited editors particularly appreciate the financial support of the ‘‘SOLWATER Project’’, (Contract No. ICA4-CT-2002-10001, http://www.psa.es/webeng/ solwater) and the ‘‘CADOX Project’’ (Contract No. EVK1-CT-2002-00122, http://www.psa.es/webeng/projects/cadox/index.html) for its financial assistance during the preparation of this Special Issue.
Sixto Malato Rodrı´guez Julia´n Blanco Ga´lvez Plataforma Solar de Almerı´a—CIEMAT Ctra. Sene´s Km. 4, Tabernas Almerı´a 04200, Spain Tel.: +34 950 387 940; fax: +34 950365015 E-mail addresses: [email protected] [email protected] Claudio A. Estrada Gasca Centro de Investigacio´n en Energı´a Universidad Nacional Auto´noma de Me´xico AP 34 Temixco Morelos 62580, Me´xico E-mail address: [email protected] Available online 11 September 2004