Yi Xiaofeng,Yang Meixia,Mo Liuda,Xu Wenkai,Wang Shuai,He Jiarui,Gu Junjie,Ou Minrui,Xu Xiaoping
Copper in drinking water causes a significant environmental problem. Composite material based on alginate hydrogel has been gaining attention in the field of Cu(II) adsorption. However, alginate-based hydrogel exhibits poor mechanical property and relative low adsorption capacity which limit their application. The present study is devoted to the modification of chitosan/calcium alginate/Fe 3 O 4 (CAF) hydrogel microsphere by NaOH solution for enhancement of Cu(II) adsorption. Results reveal that modification of CAF via NaOH solution significantly improves the mechanical strength and Cu 2+ adsorption capacity of pristine materials. FTIR and XRD analysis confirms that CAF and newly prepared materials (NACAF) are successfully prepared. SEM and EDX are employed to analyze the surface morphology and elemental composition, respectively, both before and after their loading with Cu 2+ . XPS study demonstrates adsorption mechanism is based on chelation and ion-exchange. Compressive stress-strain curves demonstrate NACAF has better mechanical performance than CAF. The adsorption kinetics of the two adsorbents follow a pseudo-second-order model. The equilibrium data were best described by Langmuir isotherm model, and the estimated maximum equilibrium sorption capacity, q
m ,is 261.31 mg/g for the NACAF, which is larger than that of CAF (145.39 mg/g). Hence, NACAF shows excellent mechanical strength and high sorption capacity for Cu 2+ . It has great potential for Cu(II) removal in aqueous solutions.
This study synthesized novel magnetic biochar (PCMN600) by KMnO 4 –NaOH combined modification using iron-containing pharmaceutical sludge to remove toxic metals from wastewater effectively. Various characterization experiments of engineered biochar showed that the modification process introduced ultrafine MnO x particles on the carbon surface and resulted in higher BET surface area and porosity along with more oxygen-containing surface functional groups. Batch adsorption studies indicated that the maximum adsorption capacities of PCMN600 for Pb 2+ , Cu 2+ and Cd 2+ were 181.82 mg/g, 30.03 mg/g and 27.47 mg/g, respectively, at a temperature of 25 °C and pH of 5.0, which were much higher than that of pristine biochar (26.46 mg/g, 6.56 mg/g and 6.40 mg/g). The adsorption datums of three toxic metal ions fitted well to the pseudo-second-order model and Langmuir isotherm, and the sorption mechanisms were identified as electrostatic attraction, ion exchange, surface complexation, cation-π interaction and precipitation. The strong magnetic properties of the engineered biochar endowed the adsorbent with remarkable reusability, and after five cycles of recycling, PCMN600 still retained nearly 80% of its initial adsorption capacities.
Lei Xia,Fang-Jing Liu,Meng-Jie Wang,Han-Bing Zhang,Jing Zhang,Yao Lu,Le-Le Qiu,Xian-Yong Wei,Yun-Peng Zhao
Production of cyclohexanone through selective hydrogenation of phenol under mild conditions has attracted much attention. Herein, a NaOH-modified Pd/WO 3 rich in oxygen vacancies for selective hydrogenation of phenol was prepared through impregnation method. The highest catalytic activity was exhibited on NaOH-Pd/WO 3 with 25 wt % addition of NaOH, and phenol achieved 100 % conversion at 90 °C and 0.7 MPa H 2 for 2 h, with a cyclohexanone selectivity of 95.3 %. The turnover frequency (TOF) of NaOH-Pd/WO 3 is approximately 3.5 times higher than that of the Pd/WO 3 . Detailed catalyst characterization and theoretical calculations reveal that the high activity and selectivity of NaOH-Pd/WO 3 for phenol hydrogenation to cyclohexanone are highly correlated with the concentration of oxygen vacancies in the catalyst. In-situ infrared and Raman analyses reveal that the OH - introduced by NaOH reacted with the lattice oxygen in WO 3 to abstract oxygen from the lattice, generating a significant number of oxygen vacancies. The possible reaction mechanisms for phenol hydrogenation were elucidated through combined density functional theory calculations and isotopic labeling experiments. This strategy of improving catalytic activity and selectivity by regulating the concentration of oxygen vacancies provides a theoretical basis for the design and optimization of industrial catalysts.
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