Guangshan Zhang

Polyacrylonitrile-based fiber modified with thiosemicarbazide by microwave irradiation and its adsorption behavior for Cd(II) and Pb(II).

A novel thiosemicarbazide modified adsorbent (PAN(MW)-TSC) based on polyacrylonitrile fiber was successfully synthesized under microwave irradiation, which was applied for the uptake of Cd(II) and Pb(II) from aqueous solution subsequently. Microwave irradiation method is a new approach to achieve the modification and it turns out that just a 30min process is enough for the anchoring of functional groups in the fiber matrix. The surface characterization was performed by fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) elemental analysis (EA) and thermogravimetric analysis (TGA), indicating that the modification was successfully accomplished. Batch adsorption experiments including equilibrium isotherms, kinetics and the effects of pH and temperature on the adsorption of Cd(II) and Pb(II) were systematically studied. Among three kinetic models, the pseudo-second-order kinetic model provides the best correlation for the process. The nonlinear resolution of the Langmuir isotherm equation has been found to show the closest fit to the equilibrium date. Thermodynamic parameters, involving △G, △H and △S were also calculated from graphical interpretation of the experimental data, which suggest that metal ions adsorption onto PAN(MW)-TSC fibers is spontaneous and exothermic. Regeneration of PAN(MW)-TSC fibers loaded with metal ions was efficiently done with 0.5M HNO3, by which the investigated adsorbent could be used reproductively for five times with a small decrease in sorption capacity. The feasible preparation of PAN(MW)-TSC fibers with high adsorption capacities opens a new perspective in the potential application for wastewater treatment.

Degradation of p-nitrophenol using CuO/Al2O3 as a Fenton-like catalyst under microwave irradiation

CuO/Al2O3 was synthesized successfully by the impregnation-deposition method and used as a heterogeneous catalyst in a microwave assisted Fenton-like process (MW/FL). The morphology and physico-chemical properties of the CuO/Al2O3 catalyst were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) analysis. The degradation of p-nitrophenol (PNP) was investigated by different processes, including microwave irradiation (MW) alone, hydrogen peroxide (H2O2) oxidation under microwave irradiation without the catalyst (MW/H2O2), a Fenton-like (FL) process, a MW/FL process and a thermally-assisted Fenton-like (TH/FL) process. The results showed that the CuO/Al2O3 catalyzed MW/FL could generate more hydroxyl radicals (˙OH) and remove PNP more effectively compared to other processes. The effects of initial pH, dosage of H2O2 and catalyst, microwave power and radiation time, and PNP concentration on the removal efficiency were also studied. The results showed that 93% removal efficiency of PNP was obtained within 6 min under optimized conditions. Moreover, the catalyst had a good stability and reusability, thus expanding the scope of non-iron based catalysts in the Fenton-like reactions.

Rapid and effective preparation of a HPEI modified biosorbent based on cellulose fiber with a microwave irradiation method for enhanced arsenic removal in water

Herein, we report a facile and rapid route for the preparation of hyperbranched polyethylenimine (HPEI) modified cellulose fiber (CellMW-HPEI) as an effective biosorbent for the removal of inorganic arsenic. Benefiting from microwave irradiation (MW), the grafting of this coating agent with a large molecular size was achieved efficiently according to FTIR, SEM and elemental analysis. The adsorption properties of the modified biosorbent including equilibrium isotherms, kinetics and the effects of pH and temperature were explored. The results revealed that the experimental data well fitted Langmuir and pseudo-second-order models. The high density of amine groups on the modified fiber surface is believed to enhance the adsorption of arsenic ions due to electrostatic attraction and surface complexation in the binding process. Compared with other biosorbents reported previously, CellMW-HPEI fibers could be promptly prepared and the uptake amounts for arsenic ions were enhanced, simultaneously. Thus, this work will help facilitate the research on novel biosorbents for the removal of arsenic from water.

Microwave-assisted synthesis of BiFeO3 nanoparticles with high catalytic performance in microwave-enhanced Fenton-like process

In this study, BiFeO3 (BFO) was successfully prepared by microwave-assisted hydrothermal synthesis (MAHS) and applied for the degradation of rhodamine B (RhB). The optimum experiment conditions for synthesizing BFOs using MAHS were obtained with the highest removal rate and degradation rate constant of RhB. Moreover, the synthesis time could be largely shortened through adopting microwave irradiation (MW). And then, in order to prove the superiority on BFO-MAHS, traditional hydrothermal method (THM) was used to compare with MAHS including the characterization analysis, the performances of produced hydroxyl radical (OH·) and the other advantages. The results reveal that BFO-MAHS has higher crystallinity, specific surface area and catalytic activity than BFO-THM due to a specific radiation effect and non-thermal effect of microwave during the BFO synthesis. These findings indicated that the feasible preparation of BFO-MAHS offers a new insight into the synthesis of high catalytic activity BFO which was applied in wastewater treatment.

Stability of BiFeO3 nanoparticles via microwave-assisted hydrothermal synthesis in Fenton-like process

Stable catalysts require high catalytic efficiency and repeated consecutive use, low mass loss, and metal leaching. This study investigated BiFeO3 (BFO) composite with high stability and reusability using a one step microwave-assisted hydrothermal method (MAHS) to decompose bisphenol A (BPA) used as the target contaminant. After six consecutive reaction cycles in microwave-enhanced Fenton-like process (MW-Fenton-like), the removal rate of BPA decreased from 94 to 87.4% with low metal leaching ratio and mass loss. The morphology, crystal, reaction kinetics, and hydroxyl radical (·OH) were used to demonstrate the high stability of BFO-MAHS. The results indicated that the benign stability and reusability of BFO-MAHS probably occurred because (1) the thermal-effect of MW improved heating rate, which led to the rapid formation stable cube structure and (2) MW mechanical vibrations existed in the preparation process, which further enhanced the cube structure. Therefore, MAHS could be used as a green and environmental friendly method to apply in catalysts synthesis, which could immensely shorten preparation time and enhance the catalytic performance with no waste production.

Adsorption and one-step degradation-regeneration of 4-amino-5-hydroxynaphthalene-2,7-disulfonic acid using biochar-based BiFeO3 nanocomposites

A microwave (MW)-assisted-H2O2 technique used to revise 4-amino-5-hydroxynaphthalene-2,7-disulfonic acid (H-acid)-saturated biochars (BCs) was investigated in detail. This method could simultaneously degrade the H-acid adsorbed in the BCs-based BiFeO3 (BFO) nanocomposites (BFO/BCs), in which BFO was used as dopant intercalated into BC, and activate the used BCs. Because H-acid could be decomposed by OH, which was generated in a coexistent system, including MW irradiation, H2O2, and BCs. Its worth noticing the adsorption capacity was (236.8mgg-1) 1.1-fold higher than that of unused BFO/BC (211.7mgg-1). It indicated that the surplus OH exhibited a cooperative effect with MW irradiation to restore H-acid-saturated BCs via the cleavage of CC bond, thereby forming carboxylic groups and the pyrolysis effect. Findings indicated that the one-step degradation-regeneration method could effectively promote the adsorption capacity of H-acid-saturated BCs in a few minutes and could thus be considered a potential technology in water treatment.