(1) A TiO2–Cu2O photocatalyst composite was formed by the growth of Cu2O on a TiO2 nucleus. (2) A p–n heterojunction is formed at the junction of TiO2 and Cu2O and reduces the forbidden bandgap. (3) The degradation rate of 171.6 mg m−3 of gaseous toluene in visible light within 3 h is greatly improved by TiO2–Cu2O.
Treatment of azo dye effluents has received increasing concerns over the years due to their potential harms to natural environment and human health. The present study described the degrading ability of the as-synthesized crystalline Al-Cu alloys for removal of high-concentration Acid Scarlet 3R in alkaline aqueous solutions and its degradation mechanism. Al-Cu alloy particles with Al/Cu ratios 19:1 were successfully synthesized by high-energy mechanical milling. Characterization results showed that 10 h mechanical alloying process could lead to the formation of crystalline Al(Cu) solid solution. Batch experiment results confirmed the excellent ability of Al-Cu alloy particles for the degradation of 3R in aqueous solution. Under a certain condition ([Al-Cu]0 = 2 g/L, [3R]0 = 200 mg/L, [NaCl]0 = 25 g/L, initial pH = 10.9), the 3R could be completely degraded within only 3 min. It was also found that the degradation reaction followed zero-order kinetics model with respect to the initial dye concentration. The intermediate compounds were identified by UV-vis, FT-IR and HPLC-MS, and a pathway was proposed. Additionally, post-treatment Al-Cu alloy particles were characterized by SEM and TEM, and the results showed that the degradation might be attributed to the corrosion effect of Al-Cu alloys.
a b s t r a c tWater disinfection using chlorine is an important step in purification that prevents dissemination of pathogens in drinking water. However, water treatment has become a challenging operation these days as persistence of pathogens after final step of chlorination was evident in many cases. The mechanism of chlorine tolerance is not yet clear. The occurrence may be due to cellular modification of the pathogens. In the present study sensitivity of microorganisms towards chlorine and various antibiotics were determined to find whether chlorine resistance supports pathogen to attain antibiotics resistance or not. Staph. aureus, Micrococcus, Enterobacter, Morganella morganii, Hafnia alvei, Rahnella aquatilis, Klebsiella and Pseudomonas aeruginosa were isolated from chlorine treated water (p > 0.05) using Membrane Filter technique. In-vitro chlorine resistance and antibiotic resistance study reveals that chlorination at sub-optimal dosage (0.5 ≤ 1.5 ppm) greatly enhances survival ability of Pseudomonas aeruginosa and Enterobacter. Bacteria from chlorine treated water were found to be more resistant to residual free chlorine and to most of the antibiotics compared to isolates obtained from the un-chlorinated pond water, leading to a conclusion that chlorination might have induced some changes in bacterial cell that ended in acquisition of chlorine tolerance and antibiotics resistance.
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