Sulfur-doped activated carbon for the efficient degradation of tetracycline with persulfate: Insight into the effect of pore structure on catalytic performance.

Sulfur-doped activated carbon has proved to be a promising metal-free catalyst for persulfate (PDS) catalytic activation for the oxidation of aqueous refractory organics. Herein, sulfur-doped porous carbon (ACS) catalysts with different pore structures and doped-S contents were prepared via a template method using d(+)-glucose as the carbon source, sulfur as the sulfur source, and nano-MgO with different particle sizes as templates. Characterization results showed that the particle size of MgO significantly affects the pore structure and doped-S content of ACSs catalysts: a sample synthesized with 20 nm MgO as template (ACS-20) presented the highest content of doped-S and a mesoporous structure, which endowed it with superior adsorption and catalytic performance toward tetracycline (TC) removal. The effect of catalyst dosage, TC concentration, PDS concentration and solution pH on TC removal efficiency were evaluated. The reaction mechanism, investigated by combination of EPR, quenching experiments and LC-MS, indicated that the reactive species included HO·, SO4˙-, and 1O2, but that 1O2 played the dominant role in TC oxidation through a non-radical oxidation pathway. In addition, the reusability and regeneration properties of the ACS-20 catalyst were also studied. This work provides a promising strategy and some theoretical basis for the design and preparation of activated carbon catalysts for advanced oxidation reactions from the viewpoint of pore structure design and S-doping.

Efficient charge separation in sulfur doped AgFeO2 photocatalyst for enhanced photocatalytic U(VI) reduction: The role of doping and mechanism insights.

Photocatalytic reduction of U(VI) in aqueous solutions has been considered as an efficient and promising technology to solve radioactive U pollution. In this work, density functional theory (DFT) calculations were firstly employed to optimize and compare the adsorption configurations combined uranium with four given photocatalysts, then their adsorption energies were - 0.97 eV for AgFeO2, - 1.15 eV for Zn doped AgFeO2, - 1.73 eV for Cu doped AgFeO2 and - 2.66 eV for S doped AgFeO2, respectively, indicating the sulfur doping plays a major role in U(VI) photoreduction. Herein, a visible light responsive efficient sulfur doped AgFeO2 photocatalyst (S doped AgFeO2) was synthesized and utilized to photocatalytic reduction of U(VI) in aqueous solutions. According to XRD, XPS and TEM analysis, the sulfur was successfully doped in AgFeO2 via the hydrothermal method. The batch experimental showed that S doping enhanced the U(VI) photoreduction activity of AgFeO2, and the S-AFO-3 photocatalyst exhibited the highest photocatalytic activity (92.57%), which was 1.5 times than that of pure AgFeO2. ESR, PL and DFT results demonstrated that the enhancement of adsorbed U(VI) photoreduction was attributed to the own unique effect of oxygen vacancy defects and efficient charge separation of S doped AgFeO2 photocatalyst. Due to its higher adsorption energies, fast-U(VI) photoreduction rate and superior chemical stability, the sulfur doped AgFeO2 photocatalyst is hoped for water remediation containing U(VI) wastewater.

Effect of activator/precursor mass ratio on sulfur-doped porous carbon for catalytic oxidation of aqueous organics with persulfate.

Sulfur-doped porous carbon has emerged as promising metal-free catalysts toward persulfate (PS) for catalytic oxidation of aqueous organics. Wherein, thermal pyrolysis with activator activation is very common for the preparation of activated carbon. However, the relationship between the mass ratio of activator/precursor and catalytic efficiency has been rarely reported. Herein, a series of sulfur-doped porous carbons (S-AC) were synthesized by one-step chemical activation of (Poly(phenylene sulphide) (PPS)) with K2CO3 as activator at K2CO3/PPS mass ratio ranging from 0 to 3. The effects of K2CO3/PPS mass ratio on its physicochemical properties and its catalytic performance for p-chlorophenol (PCP) degradation with PS were comprehensively investigated. Experiment results show that sulfur doping enhanced its catalytic activity and the sample synthesized with K2CO3/PPS mass ratio of 2 (S-AC-2) exhibited the best adsorption and catalytic performance toward PS for PCP removal. More importantly, S-AC-2 with PS could efficiently degrade various aqueous toxic organics other than PCP, and S-AC-2 showed superior catalytic activity to many recently reported advanced materials. In addition, the effects of several operate parameters, including reaction temperature, PS concentration, pH, humic acid, and inorganic ions on PCP oxidation were evaluated. By combining with the results of quenching experiments and EPR, the PS activation mechanism over S-AC-2 was revealed. Moreover, the reusability and regenerability of S-AC-2 was also studied. It indicates that S-AC-2 showed inferior reusability, but the catalytic activity of which could be fully recovered through thermal treatment at 600 °C for 2 h in N2.

Structure-activity relationship and the inhibitory effect of sulfur dioxide and water on nitrous oxide formation in selective catalytic reduction of nitrogen oxides by ammonia over hollow Co3O4@CoMn2O4 catalyst.

Hollow structures have attracted great interest in many areas for their diverse applications. In this work, a new catalyst with an open and hollow structure (Co3O4@CoMn2O4) is designed for selective catalytic reduction of nitrogen oxides by ammonia (NH3-SCR). The as-prepared hollow-structured catalyst provides a high surface area and has thin shells. Owing to its structural benefits, this catalyst exhibited enhanced nitrogen oxides (NOx) removal activity and better resistance to water and sulfur dioxide than cobalt manganate nanoparticles. It also has proved that both the Eley-Rideal and Langmuir-Hinshelwood mechanisms are present in the NH3-SCR process in this catalyst. The improved nitrogen selectivity after the addition of water and sulfur dioxide occurs owing to the inhibition of nitrous oxide formation through the Eley-Rideal and Langmuir-Hinshelwood mechanisms. The deep insight into the structure-activity relationship and the influence of water and sulfur dioxide on nitrogen selectivity provide a new perspective for constructing high-performance de-NOx catalysts.

Photocatalytic decontamination of tetracycline and Cr(VI) by a novel α-FeOOH/FeS2 photocatalyst: One-pot hydrothermal synthesis and Z-scheme reaction mechanism insight.

Tetracycline and Cr(VI) as non-biodegradable environmental contaminants have attracted increasing attention because of their chronic toxicity. In this regard, the environmentally friendly Z-scheme photocatalytic decontamination system has been widely used for contaminant treatment. Herein, a novel 3D Z-scheme α-FeOOH/FeS2 composite photocatalyst was successfully synthesized for the first time via a simple one-pot hydrothermal method. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) analyses and high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) demonstrated that the O component of the heterogeneous nanostructures formed by the FeOFe linkages in α-FeOOH was replaced by S to generate FeSFe linkages in the resulting FeS2. As expected, the novel 3D Z-scheme α-FeOOH/FeS2 composites exhibited remarkable photocatalytic activity for Cr(VI) reduction and tetracycline degradation compared to pure α-FeOOH. Photoluminesence (PL) measurement and electrochemical impedance spectroscopy (EIS), as well as density functional theory (DFT) calculations, suggested that the enhanced photocatalytic activity of the Z-scheme α-FeOOH/FeS2 composite can be attributed to the improved photo-absorption properties and the effective separation of photo-induced charge carriers caused by the Z-scheme system of the as-prepared 3D α-FeOOH/FeS2 composites. Thus, this work may facilitate the effective design of α-FeOOH-based photocatalysts.

Effect of SCR Atmosphere on the Removal of Hg0 by a V2O5-CeO2/AC Catalyst at Low Temperature.

A series of V2O5-xCeO2/AC (noted as V-Ce/AC) catalysts were synthesized by the impregnation method, which combined the advantage of AC and V-Ce. The effects of SCR atmosphere on Hg0 removal were systematically investigated at low temperature. The experimental results indicated that NO had a positive effect on Hg0 removal. In addition, an interesting experimental phenomenon was found that NH3 also showed a positive effect on Hg0 removal, which is different from many studies that have reported a negative effect of NH3 on Hg0 removal by other catalysts. NH3-TPD experiment showed that there was no apparent competition between NH3 and Hg0. An FT-IR gas analyzer and in situ DRIFTS were used to study the mechanism for the effect of NH3 on the catalyst surface and found that a small part of NH3 was overoxidized to NO2 in this catalytic system. O2 acted as a promoter in the whole process of NO and Hg0 removal. However, H2O showed an inhibiting effect on Hg0 and NO removal over V-Ce/AC catalysts, which may be caused by the competitive adsorption of H2O and pollutants (NO and Hg0). Additionally, 1 V-8Ce/AC catalyst exhibited high stability ( EHg = 87.6%, ENO = 82.84%) after 72 h reaction in SCR atmosphere at 150 °C.

Determination of Environmental Exposure to Microcystin and Aflatoxin as a Risk for Renal Function Based on 5493 Rural People in Southwest China.

Although the nephrotoxicity of microcystin and aflatoxin has been observed in animal and clinical cases, few population data are available. We conducted a cross-sectional study in Southwest China to investigate the association of renal function indicators (RFIs, including BUN, SCr, and eGFR) with exposure to microcystin and aflatoxin in 5493 members of the general population. Microcystin-LR levels in water and aquatic products and aflatoxin B1 levels in daily foods were measured by ELISA, and individual estimated daily intake (EDI) was assessed on the basis of the measurement and questionnaire. We found that participants with abnormal RFIs had a much higher mean level of microcystin-LR EDI than those with normal RFIs and that there was a significant increasing trend for abnormal rates and odds ratios of RFIs with increasing microcystin-LR EDI quartiles (p for trend = 0.000). Compared with the lowest quartile of microcystin-LR exposure, those in the highest quartile had significantly higher risks of abnormal BUN (OR = 1.80, 95% CI = 1.34-2.42), SCr (OR = 4.58, 95% CI = 2.92-7.21), and eGFR (OR = 4.41, 95% CI = 2.55-7.63), respectively, but no higher risk was found in subjects with higher AFB1 exposure. After adjustment for confounding factors, risk associations with microcystin-LR persisted. Consequently, our results suggest that microcystin, rather than aflatoxin, might be one important risk of renal-function impairment.