Liqiu Zhang

Ozonation catalyzed by the raw bauxite for the degradation of 2,4,6-trichloroanisole in drinking water.

A kind of inexpensive and environmental friendly mineral, the raw bauxite has been used successfully as a catalyst combined with ozonation in the degradation of 2,4,6-trichloroanisole (TCA). The catalyst was characterized by using various analytical techniques. X-ray powder diffraction (XRD) characterization showed that the raw bauxite containing boehmite (gamma-AlOOH), kaolinite (Al(2)Si(2)O(5)(OH)(4)) and quartz (SiO(2)), and gamma-AlOOH was the major composition. The catalytic ozonation removal effectiveness of TCA was investigated under various physicochemical conditions. Both the adsorption and the single ozonation were not effective for the degradation of TCA, and the presence of the raw bauxite in ozonation enhanced the TCA removal effectiveness. Both the hydroxyl radicals (OH) scavenging experiment and R(ct) characterization confirmed that the generation of OH was accounted for the enhancement of the degradation of TCA. The generation of OH was inhibited faintly by the presence of both natural organic matters (NOMs) and alkalinity in the natural water during catalyzed ozonation with the raw bauxite. The increasing of both the bauxite dosage and the ozone dosage enhanced the removal effectiveness of TCA. The raw bauxite was an efficient green catalyst for TCA degradation in drinking water.

Construction of a technique plan repository and evaluation system based on AHP group decision-making for emergency treatment and disposal in chemical pollution accidents.

The environmental pollution resulting from chemical accidents has caused increasingly serious concerns. Therefore, it is very important to be able to determine in advance the appropriate emergency treatment and disposal technology for different types of chemical accidents. However, the formulation of an emergency plan for chemical pollution accidents is considerably difficult due to the substantial uncertainty and complexity of such accidents. This paper explains how the event tree method was used to create 54 different scenarios for chemical pollution accidents, based on the polluted medium, dangerous characteristics and properties of chemicals involved. For each type of chemical accident, feasible emergency treatment and disposal technology schemes were established, considering the areas of pollution source control, pollutant non-proliferation, contaminant elimination and waste disposal. Meanwhile, in order to obtain the optimum emergency disposal technology schemes as soon as the chemical pollution accident occurs from the plan repository, the technique evaluation index system was developed based on group decision-improved analytical hierarchy process (AHP), and has been tested by using a sudden aniline pollution accident that occurred in a river in December 2012.

Reaction kinetics and transformation of antipyrine chlorination with free chlorine

Chlorine has been documented that it can effectively remove some pharmaceuticals. Recently, new active oxidants chlorine monoxide and molecular chlorine, which exist as free active chlorine in solution, were reported during pharmaceuticals chlorination. In this study, reaction kinetics, active oxidants, and transformation products during antipyrine chlorination were investigated with batch experiments. The reaction orders in [chlorine] were determined at various pH (6.53-7.62) and ranged from 1.13 ± 0.15 to 1.59 ± 0.08, which indicated that antipyrine chlorination is the concurrent existence of reactions appearing first-order and second-order in [chlorine]. The results by varying solution conditions (solution pH, chloride, ionic strength, and buffer concentration) show that chlorine monoxide and molecular chlorine play significant roles during the process of antipyrine chlorination. With kinetics modeling, the second-order rate constants for hypochlorous acid, chlorine monoxide, and molecular chlorine were obtained at 25 ± 2 °C (units: M(-1) s(-1)): kHOCl = 3.23 × 10(3), kCL2 = 2.86 × 10(7), kCL2O= 8.38 × 10(9) (R(2) = 0.9801). At pH 7, hypochlorous acid and chlorine monoxide are the main contributors to the degradation of antipyrine, about 80% and 20%, respectively (calculated by kHOCl, kCL2 and kCL2O. By applying these rate constants to predict the antipyrine elimination in real water matrixes (surface water, ground water), a good agreement was obtained, particularly in ground water. Moreover, liquid chromatography-tandems mass spectrometry (LC-MS/MS) and gas chromatograph-mass spectrometry (GC-MS) were used for products identification. Two main intermediate products and three stable products were observed during the process of antipyrine chlorination. The possible routes for antipyrine chlorination were proposed, which mainly consisted of halogenations, dealkylations and hydroxylations.

Efficiency and products investigations on the ozonation of 2-methylisoborneol in drinking water.

2-Methylisobomeol (MIB) is a terpenoid produced as a secondary metabolite by some cyanobacteria and actinomycetes and thus can be present in some drinking water source waters. The removal efficiency, products, and degradation pathway of MIB in drinking water by ozonation were studied. The results showed that ozone is efficient in removing MIB from an aqueous solution, regardless of the initial MIB concentration. Hydroxyl radicals (OH) scavenger experiments indicated that hydroxyl radicals are involved in MIB degradation. The degradation products of MIB were identified by gas chromatography-mass spectrometry. Camphor was identified as a primary degradation product, which was further oxidized to form other degradation intermediates, such as aldehydes, ketones, and carboxylic acids. A possible degradation pathway for the ozonation of MIB was proposed. Qualitative and quantitative analysis of the formation of aldehydes was carried out. It was found that six aldehydes are the main aldehydes products of ozonation of MIB, namely formaldehyde, acetaldehyde, propanal, butanal, glyoxal, and methyl glyoxal.

Degradation of clofibric acid in UV/chlorine disinfection process: kinetics, reactive species contribution and pathways

As a potential endocrine disruptor, clofibric acid (CA) was investigated in this study for its degradation kinetics and pathways in UV/chlorine process. The results showed that CA in both UV photolysis and UV/chlorine processes could be degraded via pseudo-first-order kinetics, while it almost could not be degraded in the dark chlorination process. The observed rate constant (kobs) in UV photolysis was 0.0078 min−1, and increased to 0.0107 min−1 combining with 0.1 mM chlorine. The kobs increased to 0.0447 min−1 with further increasing the chlorine dosage from 0.1 to 1.0 mM, and reached a plateau at higher dosage (greater than 1.0 mM). The higher kobs was obtained at acid solution rather than basic solution. Moreover, the calculated contributions of radical species to kobs indicated that the HO• contributed significantly to CA degradation in acidic conditions, while the reactive chlorine species and UV direct photolysis dominated in neutral and basic solution. The degradation of CA was slightly inhibited in the presence of HCO3− (1 ∼ 50 mM), barely affected by the presence of Cl− (1 ∼ 200 mM) and greatly suppressed by humic acid (0 ∼ 5 mg l−1). Thirteen main degradation intermediates and three degradation pathways of CA were identified during UV/chlorine process.

Comparison of varying operating parameters on heavy metals ecological risk during anaerobic co-digestion of chicken manure and corn stover

In this study, the potential ecological risk of heavy metals (Mn, Zn, Cu, Ni, As, Cd, Pb, Cr) accumulation from anaerobic co-digestion of chicken manure (CM) and corn stover (CS) was evaluated by comparing different initial substrate concentrations, digestion temperatures, and mixture ratios. Results showed that the highest volumetric methane yield of 20.3±1.4L/L reactor was achieved with a CS:CM ratio of 3:1 (on volatile solid basis) in mesophilic solid state anaerobic digestion (SS-AD). Although co-digestion increased the concentrations of all tested heavy metals and the direct toxicity of some heavy metals, the potential ecological risk index indicated that the digestates were all classified as low ecological risk. The biogasification and risk variation of heavy metals were affected by the operating parameters. These results are significant and should be taken into consideration when optimizing co-digestion of animal manure and crop residues during full-scale projects.

Application of Novel Biochars from Maize Straw Mixed with Fermentation Wastewater for Soil Health

Recently more and more researches have focused on the preparation of novel biochars for specific use in soil amendment. A series of novel biochars (MS) produced by maize straw mixed with different fermentation wastewater are introduced for their preparation and application for soil health. Preparation methods of novel biochars include physical activation, chemical activation, and blending modification. Physical activations are more efficient than chemical activations in enhancing pristine biochar’s surface structure, while the chemical activations are more capable in creating special functional groups. Blending modification method, mixing different kinds of additives with waste biomass together before pyrolysis, is usually used to increase the nutrient contents. The modified novel biochars have excellent properties such as high surface area and pore volume, rich functional groups, and high nutrient contents. The application of novel biochars to soil can improve soil fertility, promote plant growth, and increase crop yield. After the application of the novel MS biochars in soil, the contents of soil organic carbon and nitrogen were significantly increased. The addition of 5% novel biochar to soil showed the best performance for ryegrass growth and H2O2 enzymatic activity enhancement.