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Fe3O4 nanospheres (Fe3O4-S) synthesized via a facile one-pot solvothermal method were used for H2O2 activation and tetracycline (TC) elimination from aqueous solutions. It can be found that more than 80% of TC was degraded in the Fe3O4-S/H2O2 system. Besides, batch experiments were conducted to investigate the effects of different parameters such as catalyst dosages, H2O2 concentration, pH values and temperature on the degradation of TC, and these experimental results were also described by the pseudo-first-order model. Radical quenching experiments and an electron paramagnetic resonance (EPR) technique revealed that ˙OH and ˙O2−/˙HO2 were involved and ˙OH generated on the surface of Fe3O4-S played a main role in TC degradation. The XPS observations demonstrated that the surface FeII participated in the H2O2 activation through the redox reactions. Moreover, thirteen intermediate products were monitored by the LC–MS and possible degradation pathways of TC were accordingly proposed. The Fe3O4-S catalyst exhibited good reusability and the catalytic performance of it did not show any significant decrease even after five trials. It was worth noting that the optimal pH for TC degradation was expanded to neutral pH conditions by using the Fe3O4-S/H2O2 system. Additionally, Fe3O4-S was easily separated from the reaction solutions by virtue of its magnetism (66.8 emu g−1), which is beneficial for reuse of the catalysts. [ABSTRACT FROM AUTHOR]

Removing heavy metals from aqueous solutions has drawn more and more attentions these years because of their serious global health challenge to human society. To develop an adsorbent with low-cost and high-efficiency for removal of heavy metals (HMs), β-cyclodextrin (β-CD) polymers crosslinked with rigid aromatic groups were prepared and used for lead (Pb), copper (Cu) and cadmium (Cd) removal for the first time. The negatively charged β-CD polymers with large BET surface area were suitable to be used in HMs adsorption. The adsorption process completed in 5 min was well fit by Freundlich isotherm model and pseudo-second-order model. The intraparticle diffusion model was also appropriate to describe the adsorption of Pb, Cu and Cd on β-CD polymer. The maximum of adsorption capacities at 25 °C for Pb, Cu and Cd were 196.42, 164.43 and 136.43 mg/g when the initial concentration was 200 mg/L. The HMs adsorption process on the surface of β-CD polymer was an endothermic and spontaneous process. Both of the electrostatic interaction and distribution of Pb, Cu and Cd species influenced the adsorption process at different pH values. The order of removal efficiencies in multi-component adsorption for the three metal ions were Pb > Cu > Cd. The adsorption mechanisms were H + ions on hydroxyl groups exchanged with heavy metal ions and electrostatic interactions. This study indicated that β-CD polymers could be developed into effective adsorbents for rapid removal of heavy metals. [ABSTRACT FROM AUTHOR]

Consumption of water having excessive arsenic (As) contamination can cause adverse health effects on human beings. In this study, novel ultra-large zirconium oxide (ZrO 2 ) nanosheets were successfully synthesized using graphene oxide (GO) templates and their adsorption-ability was studied for arsenite (As(III)). Owing to higher values of surface area, numbers of available hydroxyl groups and strong chemisorption binding affinity towards As(III), the synthesized novel ultra-large ZrO 2 nanosheets showed high adsorption-ability for As(III) over a wide pH range. Experimental results demonstrated that the maximum adsorption-ability of the ZrO 2 nanosheets for As(III) reached to 74.9 mg/g at pH 6. BET, zeta potential, effect of initial pH, FTIR and XPS have been used to analyze the As(III) adsorption process on the ZrO 2 nanosheets. The experiments for effects of co-existing ions indicated that ZrO 2 nanosheets possessed good anti-interference ability towards co-existing ions. Furthermore, the ZrO 2 nanosheets demonstrated very fast and excellent treatment of simulated real As(III) polluted water, consequently the effluent concentration met the standard regulated by World Health Organization. This study suggested that the as-prepared ZrO 2 nanosheets could be potentially applied in practical drinking water treatment., (Copyright © 2018 Elsevier Inc. All rights reserved.)

A novel graphitic carbon nitride (g-C 3 N 4 ) nanosheet adsorbent with a large surface area, remarkable hydrophilicity and high adsorption capacity, was presented for the removal of cadmium ions (Cd 2+ ) and methylene blue (MB) from aqueous solution. Adsorption measurements were conducted systematically to study the influences of the contact time, initial concentrations of Cd 2+ and MB, temperature, and pH value. The maximum adsorption capacities of g-C 3 N 4 towards Cd 2+ and MB were 94.4 and 42.1 mg g -1 , respectively, at 318.5 K when the initial concentrations of Cd 2+ and MB were 200 and 20 mg L -1 , respectively. The adsorption kinetics fit a pseudo-second-order model. The high adsorption performance of the g-C 3 N 4 adsorbent can be attributed to the multiple adsorption sites on g-C 3 N 4 , including the π-π conjugate interactions and electrostatic attractions with pollutants in water. In addition, it is significant to achieve high adsorption performance of g-C 3 N 4 nanosheets by efficiently exposing the adsorption sites by adjusting the microstructure surface properties and dispersity in solution., (Copyright © 2016 Elsevier Ltd. All rights reserved.)