Nansheng Deng

Landfill leachate treatment by a coagulation–photooxidation process

This experimental study was conducted to investigate the effect of treatment of landfill leachate by a coagulation-photooxidation process. The effects of different dosages of coagulant and different pH values on the coagulation processes were compared. The effect of different concentrations of sodium oxalate (Na(2)C(2)O(4)) on the treatment process was also studied after the coagulation was performed using FeCl(3).6H(2)O. The experimental results show that in the pH range of 3-8, the lower the pH value, the higher the efficiency of the treatment. A 24% removal of COD (chemical oxygen demand, mg(O(2)) x l(-1)) can be attained by the addition of 1000 mg x l(-1) FeCl(3). A 31% removal of COD can be attained after 4h of irradiation alone, and a 64% removal of COD can be attained after 4h irradiation at pH 3 with the addition of 500 mg x l(-1) FeCl(3).6H(2)O.

UV-light induced photodegradation of 17α-ethynylestradiol in aqueous solutions

Abstract The photodegradation of 17α-ethynylestradiol (EE2) in aqueous solutions induced by UV-light was preliminarily studied in this paper by means of fluorescence, UV and infrared spectra. The result suggested that EE2 in aqueous solutions underwent photodegradation under irradiation with UV disinfection lamp (λ=254xa0nm, 30xa0W), but the photodegradation was not observed under high pressure mercury lamp (λ≥365xa0nm, 250xa0W). The photodegradation of 1.6–20.0xa0mg/l EE2 in aqueous solutions at a given initial pH value of 6.8 was pseudo-first order reaction. Increasing the initial concentration of EE2 lowered the photodegradation rate. The photodegradation rate of EE2 reached the lowest value at pH about 5.0, higher pH values of 6.0–8.0 benefited the photodegradation. Ferric ions can promote the photodegradation of EE2 in aqueous solutions at pH value of 2.0–5.0.

Photoproduction and determination of hydroxyl radicals in aqueous solutions of Fe(III)–tartrate complexes: a quantitative assessment

Benzene has been used as a probe to determine the photogeneration of ·OH radicals in aqueous solutions containing Fe(III) and tartrate (Tar) when they are irradiated (λu2009≥u2009313u2009nm, 250u2009W). Products were determined by HPLC. Results show that tartrate has a positive effect on the photogeneration of ·OH. The influence of pH, temperature, and concentrations of Fe(III) and Tar were systematically investigated. Production of ·OH radicals was greatest at pH 3.0. Concentrations of ·OH increased with increasing Fe(III) and tartrate concentrations, but at a certain ratio they decreased. The quantum yield of ·OH radicals at 328u2009K was nearly twice that at 298u2009K.

Degradation of atrazine photoinduced by Fe(III)-pyruvate complexes in the aqueous solution.

The composition and photochemical properties of the Fe(III)-Pyr complexes in the aqueous solution was studied in this work. Fe(III) was complexed by Pyr in the ratio of 1:3. The photochemical processes occurred in the Fe(III)-Pyr system was studied in detail. Fe(II) was the main intermediate product. DMPO was used as scavenger to determine the active radicals, such as *OH, CO3*-, CO2*-, H and RCO2* by ESR. Photodegradation of atrazine induced by the photolysis of Fe(III)-Pyr was studied and the reaction kinetics fitted the first order reaction. Parameters such as pH, the initial concentrations of Fe(III), pyruvate (Pyr) and atrazine were all investigated. Photoproducts were detected by the LC-MS and the photodegradation scheme was proposed. *OH radical was the main pathway of atrazine degradation.

Fe(III)-pyruvate and Fe(III)-citrate induced photodegradation of glyphosate in aqueous solutions

The photolysis of Fe(III)-pyruvate and Fe(III)-citrate complexes in water produces hydroxyl radicals in the presence of dissolved oxygen, and can promote the oxidation of organic compounds. The photodegradation of glyphosate with Fe(III)-pyruvate and Fe(III)-citrate complexes was investigated under irradiation at λu2009≥u2009365u2009nm. The effect of initial concentration of glyphosate, the initial pH value, and the Fe(III)/carboxylate ratio were examined. Upon irradiation of glyphosate aqueous solution with the complexes in the acidic range of natural waters, the bioavailable orthophosphate could be released from degradation of glyphosate. The amount of orthophosphate increased with increasing Fe(III)/carboxylate ratio.