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The coal fly ash (CFA)/coal fly ash modified by sulfuric acid (MCFA)-conditioned sludge dewaterability was investigated in this study. Specific resistance of filtration (SRF) was used to assess the sludge dewaterability. Extracellular polymeric substance (EPS) was determined in attempt to explain sludge conditioning process. The results showed that SRF of the sludge significantly decreased with coal fly ash addition, and the MCFA showed much stronger conditioning capacity than the raw coal fly ash. Under a MCFA dosage of 36g.L-1, the SRF of the sludge decreased from 1.18×1012 to 6.47×1010 m.kg1, and EPS concentration of the sludge decreased from 32.64 to 17.55mg.L-1. The sludge conditioning mechanisms with MCFA mainly included improving adsorption bridging and providing the water transmitting passages by skeleton builder.

Coal fly ash (CFA) modified by sulfuric acid treatment was used as a low-cost adsorbent for removing natural organic matter (NOM) in an artificial lake. The specific surface areas and SEM images of modified coal fly ash (MCFA) and CFA were observed. Two equilibrium models were compared to evaluate NOM removal process with a better fitting using the Freundlich model. Kinetic studies were also carried out to fit the experimental data. The pseudo second-order provided the highest coefficients of determination.

Coal fly ash (CFA) was modified by hydrothermal treatment using NaOH solutions for zeolite synthesis. The XRD patterns of zeolite and coal fly ash are presented. The synthesized zeolite was investigated for adsorption of methylene blue（MB）in aqueous solution. It was shown that fly ash and the modified forms could effectively absorb MB. The adsorption isotherm could be described by Freundlich isotherm equations. The pseudo second-order kinetics would be better for fitting the dynamic adsorption of MB.

The present study investigated the removal of As(III) from low-arsenic water through adsorption on amorphous mesoporous TiO2. The mesoporous TiO2 adsorbent size was 3.92 nm as calculated by adsorption average pore width. The Brunauer–Emmett–Teller surface area was 205 m2/g. A 0.2 g adsorbent treatment during five hours resulted in less than 4 μg/L remaining As(III) in the water, and nearly 84% of As(III) in the solution were removed in only 20 min. The As(III) adsorption kinetics data were well described by the pseudo-second-order model. The maximum adsorption pH value of 9.3 coincided with the first pK 1 dissociation constant of H3AsO3 of 9.22. The Dubinin-Radushkevich and Langmuir isotherms provided maximum adsorption capacity of 4.57 and 4.79 mg/g, respectively, under low equilibrium concentration. These values possibly indicate the excellent capacity of amorphous mesoporous TiO2 on As(III) removal from low-arsenic water. Given by the b-value of Langmuir isotherm under different pH, the averag...

Coal fly ash (CFA) was modified by hydrothermal treatment using NaOH solutions for zeolite synthesis. The XRD patterns of zeolite and coal fly ash are presented. The synthesized zeolite was investigated for adsorption of heavy metal ions in aqueous solution. It was shown that fly ash and the modified forms could effectively absorb heavy metals. The adsorption isotherm could be described by Freundlich isotherm equations. The pseudo second-order kinetics would be better for fitting the dynamic adsorption of Cu2+ and Cd2+.

As(III) removal from low-arsenic concentration drinking water treated by coagulation with mixture titanium tetrachloride and titanium sulfate as coagulants were studied in this paper. Without any pre-oxidation process, the residual concentration of As(III) after treated by the coagulant (concentration of 25mg/L) was less than 4μg/L,which can be satisfied the most rigid guideline for arsenic maximum contaminant level (MCL) proposed by WHO or USEPA. Operated with rapid water dynamics will get the better efficiency for As(III) removal. In the pH range of 3-6 the variation of As(III) removal efficiency was minimal, but the As(III) removal declined gradually with the increase of pH while in the alkaline range. Ferrous salts can significantly increase the efficiency of As(III) removal by coagulation treatment with mixed titanium salts as coagulant.

Nitrogen doped TiO2 (N/TiO2) photocatalysts were prepared using a mechanochemica1 method with raw amorphous TiO2 as precursors and various nitrogenous compounds doses (NH4F, NH4HCO3, NH3·H2O, NH4COOCH3, and CH4N2O). The photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflection spectra (UV-Vis-DRS). Their photocatalytical activities were evaluated with the degradation of p-nitrophenol and methyl orange under UV or sunlight irradiation. The catalysts had a strong visible light absorption which corresponding to doped nitrogen and consequent oxygen deficient. Concentration of the nitrogen substances also affected the visible light adsorption of the TiO2. The XPS results indicated the doped nitrogen in the TiO2 may exist in the formation of O2Ti−N−H and/or O2Ti−N, nitrogen was in form of interstitial atom. The results of photocatalytic activity showed the visible light adsorption mechanisms, as the doped nitrogen species gave rise to a mid-gap level slightly above the top of the (O-2p) valence band, but not from the mixed band gap of the N-2p and O-2p electronic levels.

The photochemical degradation mechanisms of an azo dye Direct Red 4BS and Methyl Orange on hematite in the presence of H2O2 were investigated. The decolorization of azo dyes was attributed to the forming surface complex between specific bond of the dyes and hematite, which facilitate the electron transfer from hematite to azo bond. No mineralization of azo dyes occurred in the presence of visible irradiation, only chromogenic group destroyed in the photo-chemical reaction process. Surface complex between azo dyes and hematite will be destroyed under alkaline solution which suggested the active site or the formed surface complex had been destroyed by OH–. Chemical adsorption of the azo dyes on hematite was critical factor which affect the decolorization efficiency of the photoreaction.