A sequential adsorption/photocatalytic regeneration process to remove tartrazine, an azo-dye in aqueous solution, has been investigated. The aim ofthis work was to compare the effectiveness of an adsorbent/photocatalyst composite-TiO2 deposited onto activated carbon (AC) - and a simple mixture of powders of TiO2 and AC in same proportion. The composite was an innovative material as the photocatalyst, TiO2, was deposited on the porous surface ofa microporous-AC using metal-organic chemical vapour deposition in fluidized bed. The sequential process was composed of two-batch step cycles: every cycle alternated a step of adsorption and a step of photocatalytic oxidation under ultra-violet (365 nm), at 25 degreeC and atmospheric pressure. Both steps, adsorption and photocatalytic oxidation, have been investigated during four cycles. For both materials, the cumulated amounts adsorbed during four cycles corresponded to nearly twice the maximum adsorption capacities qmax proving the photocatalytic oxidation to regenerate the adsorbent. Concerning photocatalytic oxidation, the degree of mineralization was higher with the TiO2/AC composite: for each cycle, the value of the total organic carbon removal was 25% higher than that obtained with the mixture powder. These better photocatalytic performances involved better regeneration than higher adsorbed amounts for cycles 2, 3 and 4. Better performances with this promising material - TiO2 deposited onto AC - compared with TiO2 powder could be explained by the vicinity of photocatalytic and AC adsorption sites.

Preparation of activated carbon from sewage sludge is a promising approach to produce cheap and efficient adsorbent for pollutants removal as well as to dispose of sewage sludge. The first objective of this study was to investigate the physical and chemical properties (BET surface area, ash and elemental content, surface functional groups by Boehm titration and weight loss by thermogravimetric analysis) of the sludge-based activated carbon (SBAC) so as to give a basic understanding of its structure and to compare to those of two commercial activated carbons, PICA S23 and F22. The second and main objective was to evaluate the performance of SBAC for single and competitive adsorption of four substituted phenols (p-nitrophenol, p-chlorophenol, p-hydroxy benzoic acid and phenol) from their aqueous solutions. The results indicated that, despite moderate micropore and mesopore surface areas, SBAC had remarkable adsorption capacity for phenols, though less than PICA carbons. Uptake of the phenolic compound was found to be dependent on both the porosity and surface chemistry of the carbons. Furthermore, the electronegativity and the hydrophobicity of the adsorbate have significant influence on the adsorption capacity. The Langmuir and Freundlich models were used for the mathematical description of the adsorption equilibrium for single-solute isotherms. Moreover, the Langmuir-Freundlich model gave satisfactory results for describing multicomponent system isotherms. The capacity of the studied activated carbons to adsorb phenols from a multi-solute system was in the following order: p-nitrophenol > p-chlorophenol > PHBA > phenol.

Environmental contamination is one of the important issues that the world is confronting today, and it is expanding with each passing year and leading to grave and harmful effect to the earth. At present, the air contains various pollutants like CO, chlorofluorocarbons, volatile organic compounds, hydrocarbons, and nitrogen oxides. Water and soil are also contaminated with organic and inorganic compounds, the major sources for water and soil contamination are sewage water, industrial effluents, random use of pesticides, fertilizers, and oil spills. In parallel, the rapid growth of nanotechnology has gained a great deal of interest in the applications of nanomaterials potential in improved systems for monitoring and cleanup including all the three phases of environment . It can develop the pollutants sensing and detection and help in the improvement of novel remediation technologies. Nanomaterials are excellent adsorbents, catalysts and sensors due to their large specific surface areas and high reactivates. This review firstly sheds the light on the definition of nanoparticles, and the nanotechnology concept, the fundamental properties, classification, and fields of nanotechnology applications. Then it focuses broadly on the application of nanotechnology in environmental fields, in particular, its application in air pollution monitoring and remediation and its future trend in this field.

Agricultural wastes such as rice straw, sugar beet, and sugarcane bagasse have become a critical environmental issue due to growing agriculture demand. This study aimed to investigate the valorization possibility of sugarcane bagasse waste for activated carbon preparation. It also aimed to fully characterize the prepared activated carbon (BET surface area) via scanning electron microscope (SEM) and in terms of surface functional groups to give a basic understanding of its structure and to study the adsorption capacity of the sugarcane bagasse-based activated carbon using aqueous methylene blue (MB). The second main objective was to evaluate the performance of sugarcane bagasse-based activated carbon for indoor volatile organic compounds removal using the formaldehyde gas (HCHO) as reference model in two potted plants chambers. The first chamber was labeled the polluted chamber (containing formaldehyde gas without activated carbon) and the second was taken as the treated chamber (containing formaldehyde gas with activated carbon). The results indicated that the sugarcane bagasse-based activated carbon has a moderate BET surface area (557 m 2 /g) with total mesoporous volume and microporous volume of 0.310 and 0.273 cm 3 /g, respectively. The prepared activated carbon had remarkable adsorption capacity for MB. Formaldehyde removal rate was then found to be more than 67% in the treated chamber with the sugarcane bagasse-based activated carbon. The plants' responses for this application as dry weight, chlorophyll contents, and protein concentration were also investigated.Implications: Preparation of activated carbon from sugarcane bagasse (SCBAC) is a promising approach to produce cheap and efficient adsorbent for gas pollutants removal. It may be also a solution for the agricultural wastes problems in big cities, particularly in Egypt. MB adsorption tests suggest that the SCBAC have high adsorption capacity. Formaldehyde gas removal in the plant chambers indicates that the SCBAC have potential to recover volatile gases. The results confirmed that the activated carbon produced from sugarcane bagasse waste raw materials can be used as an applicable adsorbent for treating a variety of gas pollutants from the indoor environment.

This paper describes a preliminary evaluation of the performance of carbonaceous materials prepared from sewage sludges (SBCMs) in a hybrid water treatment process based on adsorption and catalytic wet air oxidation; phenol was used as the model pollutant. Three different sewage sludges were treated by either carbonisation or steam activation, and the physico-chemical properties of the resultant carbonaceous materials (e.g. hardness, BET surface area, ash and elemental content, surface chemistry) were evaluated and compared with a commercial reference activated carbon (PICA F22). The adsorption capacity for phenol of the SBCMs was greater than suggested by their BET surface area, but less than F22; a steam activated, dewatered raw sludge (SA_DRAW) had the greatest adsorption capacity of the SBCMs in the investigated range of concentrations (<0.05 mol L(-1)). In batch oxidation tests, the SBCMs demonstrated catalytic behaviour arising from their substrate adsorptivity and metal content. Recycling of SA_DRAW in successive oxidations led to significant structural attrition and a hardened SA_DRAW was evaluated, but found to be unsatisfactory during the oxidation step. In a combined adsorption-oxidation sequence, both the PICA carbon and a selected SBCM showed deterioration in phenol adsorption after oxidative regeneration, but a steady state performance was reached after 2 or 3 cycles.