Xujin Gong

Removal of Cr(VI) from low-temperature micro-polluted surface water by tannic acid immobilized powdered activated carbon.

In this study, food-grade tannic acid-immobilized powdered activated carbon (TA-PAC) was prepared, and adsorption of Cr(VI) (0.500 mg/L) onto TA-PAC as a function of pH, contact time, adsorption capacities and adsorption isotherms at 280 K was investigated. The results indicated that the immobilization process introduced abundant acid functional groups. The adsorption capacity of TA-PAC was found to be pH-dependent, and the optimal pH value was found to be 4.0. The equilibrium time was 240 min for TA-PAC. Adsorption data for total chromium were modeled using both two-parameter and three-parameter isotherm models. Freundlich and linear forms of three-parameter models yielded the best results for all of the data. Desorption studies of immobilized material suggested that the immobilization of food-grade tannic acid is steady. The adsorption mechanism of Cr(VI) on TA-PAC was assumed to be a comprehensive process consisting of surface reduction of Cr(VI), esterification between catechol and chromate, and ion exchange.

Adsorption characteristics of arsenic from micro-polluted water by an innovative coal-based mesoporous activated carbon.

An innovative coal-based mesoporous activated carbon (NCPAC) was prepared by re-agglomeration, oxidation and two-step activation using coal-blending as precursor. Adsorption capacities of As(III) and As(V) ions (<0.5mg/L) onto NCPAC as a function of pH, adsorbent dose, initial arsenic concentrations, contact time, and adsorption isotherms at 7°C was investigated. The innovative methods promoted total pore volume (1.087cm(3)/g), mesoporosity (64.31%), iodine numbers (1104mg/g), methylene blue (251.8mg/g) and ash contents (15.26%). The adsorption capacities of NCPAC for As(III) and As(V) were found to be strongly dependent on pH and contact time. The optimal pH value was 6. The equilibrium time was 60min for adsorption of As(III) and As(V) by NCPAC. The Langmuir model fitted the experimental data well for both As(III) (R(2)=0.9980) and As(V) (R(2)=0.9988). Maximum adsorption capacities of As(III) and As(V) (C0=0.50mg/L) by NCPAC were 1.491 and 1.760mg/g, respectively.

Study of the adsorption of Cr(VI) by tannic acid immobilised powdered activated carbon from micro-polluted water in the presence of dissolved humic acid.

The adsorption of Cr(VI) (0.500 mg/L) onto food-grade tannic-acid immobilised powdered activated carbon (TA-PAC) in the presence of dissolved humic acid (DHA) was investigated at 280 K as a function of pH, along with the adsorption capacities and the adsorption isotherms for chromium ions. The results showed that the presence of DHA improved the adsorption capacities of Cr(VI) and its reduction product (Cr(III)) over a wide pH range (4.0-8.0). The main mechanism for metal-DHA complexation in the Cr(VI) system was the reduction of Cr(VI) followed by complexation between Cr(III) and DHA. The Freundlich isotherms yielded the best fits to all data (R(2)=0.9951, qm=5.639 mg/g) in the presence of DHA. The adsorption mechanisms of Cr(VI) onto TA-PAC in the presence of DHA were summarized into three categories: (i) binding by anion adsorption, (ii) Cr(VI) reduction followed by Cr(III) adsorption, and (iii) adsorption of Cr(III)-DHA complexes.

Optimization of the UV/chlorine process for ammonia removal and disinfection by-products reduction

AbstractIn this study, response surface methodology was used to investigate the efficiency of the UV/chlorine process for ammonia removal and disinfection by-products reduction. A five-level three-factorial central composite design was employed to study the interaction of three independent variables, including the Cl/N molar ratio, UV dose, and pH. Ammonia removal rate and trihalomethanes (THMs) formation rate were the target responses and two quadratic models were established. The optimum conditions of maximum ammonia removal and minimum THMs formation were: Cl/N molar ratio 0.99, UV dose 93.10 mJ cm−2, and pH value 7.88, respectively. Under these conditions, the predicted ammonia removal rate and THMs formation rate by the two quadratic models were 64.03 and 34.87%, which were consistent with the verification experimental results.

Draft Genome Sequences of Acinetobacter harbinensis Strain HITLi 7T, Isolated from River Water

Acinetobacter harbinensis HITLi strain 7(T), isolated from river water, has the ability to remove ammonium and organic chemicals at 2°C. The genome sequences might be useful for investigating the low-temperature adaptability and nitrogen or organic chemical metabolism.

Evaluation of the effect of a hydraulic impeller in a flocculation basin on hydrodynamic behavior using computational fluid dynamics

AbstractThis study investigates the hydraulic impeller in a flocculation basin, which is important to facilitate uniformity in the sedimentation basin and to improve sedimentation efficiency. The experiments were conducted in a Perspex vessel that is 100 × 100 × 700 mm (length × width × height), with an effective depth of 600 mm. A high resolution phase-resolved computational fluid dynamics (CFD) simulation technique was used. The mean velocity, root mean square velocity, and turbulent kinetic energy of different flow patterns were investigated. The commercial CFD software was used to process the data generated from the k–e model. The velocity of the flow pattern can be predicted by k–e model. The CFD software FLUENT was used to simulate the hydraulic impeller under various combinations. The turbulence kinetic energy k, the effective energy dissipation e, velocity gradient G, and pressure were used as criteria to evaluate flocculation effects, to interpret the complex phenomenon in the course of flocculat...

Preparation, characterization, and application of sludge with additive scrap iron-based activated carbons

AbstractActivated carbons were prepared using sewage sludge with additive scrap iron as precursor and ZnCl2 as activator by pyrolysis method. By examining the effects of pyrolysis temperature, pyrolysis time, impregnation ratio, and scrap iron dosage on the adsorption performance of the sludge with additive scrap iron-based activated carbon, the optimum preparation conditions were obtained as following: pyrolysis temperature of 550°C, pyrolysis time of 50 min, impregnation ratio of 3:1, and scrap iron dosage of 0.5 wt %. The physical and chemical characteristics of the activated carbons produced from sewage sludge with and without additive scrap iron were determined and compared. The results showed that adding scrap iron into sewage sludge could enhance the pyrolysis of sludge and significantly improve the formation of mesopores in the produced activated carbon. In the adsorption experiments applying the prepared activated carbons to the treatment of azo dye wastewater, the adsorption data fitted the Lang...