Xiaozhi Wang

Floating photocatalyst of B-N-TiO2/expanded perlite: a sol-gel synthesis with optimized mesoporous and high photocatalytic activity.

Optimized mesoporous photocatalyst endowed with high specific surface area and large pore size was synthesized by sol–gel method. These large pore mesoporous materials (33.39 nm) were conducive to the movement of larger molecules or groups in pore path and for effective use of active sites. The high specific surface area (SBET, 99.23 m2 g−1) was beneficial to catalytic oxidation on the surface. Moreover, B and N co-doped anatase TiO2 in the presence of Ti–O–B–N and O–Ti–B–N contributed to the pore structure optimization and enhanced photoresponse capacity with a narrow band gap and red shift of absorption. The obtained materials with floating characteristics based on expanded perlite (EP) showed favorable features for photocatalytic activity. The best RhB photodegration rate of B–N–TiO2/EP (6 mg/g, 24 wt% TiO2) reached 99.1% after 5 h in the visible region and 99.8% after 1 h in the UV region. The findings can provide insights to obtain floatable photocatalysts with simple preparation method, optimized mesoporous, co-doping agents, as well as good photocatalytic performance, coverable and reusability. B–N–TiO2/EP has potential applications for practical environmental purification.

Simultaneous reductive and sorptive removal of Cr(VI) by activated carbon supported β-FeOOH

An activated carbon (AC)-supported nanocomposite was prepared by precipitating β-FeOOH onto KOH activated soybean meal-derived biochar (SYBK). The as-prepared β-FeOOH/SYBK composites were characterized by N2-Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), X-ray diffractions (XRD) and X-ray photoelectron spectroscopy (XPS). XRD results confirmed that β-FeOOH was impregnated by AC. The chromate (Cr(VI)) removal capacity was investigated in a batch experiment with different conditions. The ratios of β-FeOOH and AC were compared for Cr(VI) removal and a loading quantity of 20 wt% β-FeOOH was considered as the most efficient amount. This was possibly ascribed to it having the highest surface area (670.65 m2 g−1) of the β-FeOOH/SYBK nanocomposites. It was found that 20β-FeOOH/SYBK could remove as much as 96% Cr(VI) at pH 1–2 with 2 mmol L−1 EDTA and 2.0 g L−1 nanocomposites. The maximal Cr(VI) removal by 20β-FeOOH/SYBK was 37.04 g kg−1, as estimated by a Langmuir isotherm model. The removal mechanisms were examined by studying the speciation of Cr on sorbents as well as in aqueous solution. The XPS analysis of spent sorbents and chemical speciation of Cr in aqueous solutions revealed that partial Cr(VI) was reduced to Cr(III) on sorbents and in aqueous solution. This suggests that Cr(VI) can be removed by simultaneous sorption and reduction by the as-prepared nanocomposites.

Magnetic Activated-ATP@Fe 3 O 4 Nanocomposite as an Efficient Fenton-Like Heterogeneous Catalyst for Degradation of Ethidium Bromide

Magnetic attapulgite-Fe3O4 nanocomposites (ATP-Fe3O4) were prepared by coprecipitation of Fe3O4 on ATP. The composites were characterized by scanning electron microscopey, X-ray diffractometry, Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy, energy dispersive spectrometer and transmission electron microscopy. Surface characterization showed that Fe3O4 particles with an average size of approximately 15 nm were successfully embedded in matrix of ATP. The capacity of the Fe3O4-activated ATP (A-ATP@Fe3O4) composites for catalytic degradation of ethidium bromide (EtBr, 80 mg/L) at different pH values, hydrogen peroxide (H2O2) concentrations, temperatures, and catalyst dosages was investigated. EtBr degradation kinetics studies indicated that the pseudo-first-order kinetic constant was 2.445 min−1 at T = 323 K and pH 2.0 with 30 mM H2O2, and 1.5 g/L of A-ATP@Fe3O4. Moreover, a regeneration study suggested that A-ATP@Fe3O4 maintained over 80% of its maximal EtBr degradation ability after five successive cycles. The effects of the iron concentrations and free radical scavengers on EtBr degradation were studied to reveal possible catalytic mechanisms of the A-ATP@Fe3O4 nanocomposites. Electron Paramagnetic Resonance revealed both hydroxyl (∙OH) and superoxide anion (∙O2−) radicals were involved in EtBr degradation. Radical scavenging experiment suggested EtBr degradation was mainly ascribed to ∙OH radicals, which was generated by reaction between Fe2+ and H2O2 on the surface of A-ATP@Fe3O4.

Carboxymethyl cellulose stabilized ZnO/biochar nanocomposites: Enhanced adsorption and inhibited photocatalytic degradation of methylene blue

Biochar(BC)-supported nanoscaled zinc oxide (nZO) was encapsulated either with (nZORc/BC) or with no (nZOR/BC) sodium carboxymethyl cellulose (CMC). The X-ray diffraction and ultraviolet (UV)-visible-near infrared spectrophotometry revealed that nZO of 16, 10, and 20 nm with energy band gaps of 2.79, 3.68 and 2.62 eV were synthesized for nZOR/BC, nZORc/BC and nZO/BC, respectively. The Langmuir isotherm predicted saturated sorption of methylene blue (MB) was 17.01 g kg-1 for nZORc/BC, over 19 times greater than nZOR/BC and nZO/BC. Under UV irradiation, 10.9, 61.6, 83.1, and 41.6% of MB were degraded for nZORc/BC, nZO/BC, nZOR/BC and BC. The scavenging experiment revealed hydroxyl radical dominated CMC degradation. Exogenous CMC (2 g L-1) increased MB sorption from 10.6% to 73.1%, but decreased MB degradation from 80.7% to 41.1%, relative to nZOR/BC. Thus, CMC could increase MB sorption by electrostatic attraction and other possible mechanisms. The compromised MB degradation may be ascribed to reduced availability of hydroxyl and superoxide radicals to degrade MB, and increased band gap energy of ZnO.

β–cyclodextrin functionalized biochars as novel sorbents for high-performance of Pb2+ removal

The aim of this study was to synthesize the functionalized biochars with β-cyclodextrin (β-CD), compare the two kinds of adsorption capability, and try to explore the possible mechanism for the adsorption Pb2+ by β-CD functionalized rice straw and palm biochars in the aquatic environment. The performance of the functionalized biochars was matched against the activated and raw biochars. Rice straw biochar loaded with β-CD performed better than functionalized palm biochar with the adsorption capabilities of 130.60 mg/g and 90.30 mg/g at Pb2+ concentration of 3000 mg/L and 2000 mg/L, respectively. Maximum adsorption capability of functionalized rice straw and palm biochars from the Langmuir isotherms were all fitted out to be 131.24 mg/g and 118.08 mg/g for Pb2+. Kinetics and thermodynamics are combined to investigate the Pb2+ removal by the two functionalized biochars, e.g, Pb2+ is mainly removed by chemical process for functionalized palm biochar, whereas by both physical and chemical factors for functionalized rice straw biochar.

Preparation and application synthesis of magnetic nanocomposite using waste toner for the removal of Cr(VI)

In this study, a novel magnetic nanocomposite was prepared using waste toner (WT) through high temperature decomposition, and calcination was conducted in different atmospheres (air, ammonia, and vacuum). WT calcined in ammonia (WT(NH3)), and it was then utilized as an efficient absorbent for the reduction of Cr(VI) in aqueous solutions; a batch experiment with different conditions was performed to investigate its Cr(VI) removal ability. The effects of two pH-regulating acid (HCl and H2SO4) treatments were also studied. It was found that WT(NH3) could remove about 99% Cr(VI) at pH 2 under H2SO4 treatment. The XRD and TEM results coupled with VSM results confirmed that WT(NH3) is an Fe3O4/Fe2N nanohybrid, which possesses excellent water-dispersibility and remarkable magnetic properties. XPS analysis showed the presence of Cr(VI) and Cr(III) on the surface of WT(NH3), which indicated that Cr(VI) was reduced to Cr(III). Furthermore, H2SO4 regulation also promoted the reduction of Cr(VI) by WT(NH3), and this reduction was higher than that obtained by HCl regulation.

Adsorption and reduction of hexavalent chromium on magnetic greigite (Fe3S4)-CTAB: leading role of Fe(II) and S(−II)

In this study, a facile one-step route was used to synthesize a novel magnetic mesoporous greigite (Fe3S4)-CTAB composite, which was utilized to remove hexavalent chromium (Cr(VI)). The optimized Fe3S4-CTAB0.75 composite with a CTAB dosage of 0.75 g possessed the maximum specific surface, showing the highest Cr(VI) adsorption capacity of 330.03 mg g−1. The mechanism analysis revealed that Fe(II) and S(−II) were critical for the reduction of Cr(VI). CTAB can promote the removal of Cr(VI) by Fe3S4-CTAB composites, possibly due to increased S(−II) concentration, better dispersion of nanoparticles, and greater zeta potential. Besides, there is mild effect of Fe0 on Cr(VI) removal, which is confirmed by the disappearance of the Fe0 peak from the XPS analysis. The pseudo-second-order kinetic model could explain the Cr(VI) removal processes well. The adsorption of Cr(VI) at different initial concentrations was more consistent with a Langmuir isotherm. The existence of H+ was beneficial for Cr(VI) removal by Fe3S4-CTAB0.75. Our work confirmed that the obtained Fe3S4-CTAB0.75 composites exhibit considerable potential for Cr(VI) removal from aqueous solution.