Visible light photocatalytic degradation of methylene blue and rhodamine B over silver-doped titanium dioxide nanocomposites supported on Fuller's earth.

Silver-doped-titanium dioxide nanoparticles supported on Fuller's earth, prepared by the sol-gel method, were characterized with XRD, TGA, zeta potential, SEM, EDX, TEM, XPS, photoluminescence and UV-DRS measurements. The material, Ag-TiO2-Fuller's earth (AgTF), was tested for photocatalytic activity concerning the degradation of rhodamine B (RhB) and methylene blue (MB) in aqueous solution under visible light irradiation with pH, catalyst dosage, and dye concentration as the process variables. The degradation kinetics indicated pseudo-first-order kinetics with rate constant of (i) 0.55 min-1with 0.12 gL-1AgTF loading, 10-5 M MB at pH 9, and (ii) 0.53 min-1 with 0.08 g L-1 AgTF loading, 5 × 10-5 M RhB at pH 8. The methylene blue degradation was maximum (98.66%) for AgTF loading of 0.12 g L-1 while the maximum RhB degradation (96.34%) was attained with AgTF loading of 0.08 g L-1. With 5 × 10-6M MB concentration, the degradation achieved was 98% in 45 min and 100% in 60 min. One hundred per cent degradation of the dye, RhB (1 × 10-6 M) could be achieved in 30 min with 0.08 g L-1 AgTF at pH 8. The use of Fuller's earth, a cheap, abundant and large surface area support, increases the adsorbability of the dye on the catalyst surface and hence promotes the degradation. The catalyst could be removed easily from the reaction mixture and reused for up to five cycles without any significant decrease in activity. Scavengers such as triethanolamine (TEOA), p-benzoquinone (BQ) and isopropyl alcohol (IPA) were utilized to get some insight into the photocatalysis mechanism.

Treatment of crude oil contaminated wastewater via an electrochemical reaction.

A cost-effective and catalyst-free approach for the treatment of oil field formation water has been extensively explored in this work. ZnO NPs were synthesized via an electrochemical reaction using hydrogen peroxide as the electrolyte. The XRD and TEM analysis depicted the high purity and wurtzite hexagonal structure of ZnO NPs with an average size of 35 ± 5 nm. TGA data showed the thermal stability of the synthesized material up to 750 °C. The efficiency of the removal of hydrocarbons from formation water by the combination of electrochemical reaction and synthesized ZnO NPs was monitored by GC-MS and FTIR. GC-MS analysis revealed that out of 214 compounds (present in the untreated sample), a total of 131 compounds were adsorbed by ZnO NPs. Further, the absence of any compound in the chromatogram of the treated sample attests that the rest of the compounds were completely or partially degraded by electrochemical degradation reaction. Moreover, this technique overcomes some of the important drawbacks of the existing techniques in the area of electrochemical research, such as the generation of toxic byproducts, unwanted side reactions, and involvement of hazardous chemicals.