S defect-rich MoS2 aerogel with hierarchical porous structure: Efficient photocatalysis and convenient reuse for removal of organic dyes.

To avoid the difficulty of separating solids from liquids when reusing powder photocatalysts, 3D stereoscopic photocatalysts were constructed. In this study, three-dimensional S defect-rich MoS2 hierarchical aerogel was prepared by chemical cross-linking of functional ultrathin 2D MoS2. Its phase, micro-morphology and structure were characterized, and it was used in the study of photocatalytic degradation of organic pollutants. Of the samples tested, MS@CA-3 (i.e., defect-rich 3D MoS2 aerogel with a loading of 30 mg of defect-rich MoS2) exhibited the best photocatalytic activity due to its suitable load, good light transmission, and a degradation rate of up to 91.0% after 3 h. In addition, MS@CA-3 aerogel offers high recyclability and structural stability, and the degradation rate of the organic pollutant methylene blue decreases only 9.8% after more than ten cycles of photocatalytic degradation. It combines the high catalytic performance of S defect-rich 2D MoS2 and the convenient reusability of hierarchical porous aerogel. This study provides valuable data and a reference for the practical promotion and application of photocatalytic technology in the field of environmental remediation.

Photocatalytic mechanism conversion of titanium dioxide induced via surface interface coordination.

Photocatalytic removal of organic pollutants is a promising pollution treatment technology from the aspect of carbon neutrality. The complex diversity of actual wastewater components, as opposed to single-component systems, can significantly affect photocatalytic mechanisms. In this study, complex pollutant systems were created using various coordinating agents, and the effects of P25 on the photocatalytic removal of methyl orange (MO) in these systems and corresponding photocatalytic mechanism were investigated. The results show that photocatalytic removal of MO by P25 using ligands is significantly more efficient, especial removal of MO by the EDTA-P25 (P-E2.5) coordination system resulted dramatically improved MO removal (97.4% versus 12.3% achieved by pure P25 after 15 min), with the reaction rate improved 23.8-fold. Theoretical calculations show that the effective coordination bonds formed by the coordinating agent and Ti atoms reduce the adsorption energy of P25 for MO. In addition, introduction of the coordinating agent EDTA reduces the transition state energy during the MO degradation process and greatly accelerates the reaction rate, and the conduction band position of the EDTA-P25 coordination system shifts to a more negative potential, which induces to the generation of •O2- for effective MO degradation.

Novel sodalite stabilized zero-valent iron for super stable and outstanding efficiency in activating persulfate for organic pollutants fast removal.

In this study, novel porous sodalite (SOD) was synthesized through Reactive Oxidation Species (ROS) route from industrial waste lithium silicon fume (LSF) to stabilize nZVI (SOD@nZVI), and used as an outstanding persulfate (PS) activator for efficient organic degradation. Characterization results revealed nZVI evenly distributed on SOD via ion-exchange, and the fabricated SOD@nZVI exhibited high stability and superior reactivity over a wide pH range of 2-12 during oxidation reaction. The mechanism responsible for fast organic degradation in the SOD@nZVI+PS system was carefully investigated, and weak magnetic field (WMF) and friction were found to contribute to improved SOD@nZVI performance. The fast redox cycle of Fe2+/Fe3+ on SOD@nZVI can be stimulated by changing the mixing condition and altering the friction layer to harvest mechanical energy during the reaction, which can maximum persulfate activation to generate more reactive radicals for organic fast degradation. This study is of great significance, as it offers a practical route turning waste into excellent PS activator for in-situ organic pollution remediation, as well as proposing a new idea to maximum PS activation performance by manipulating the inner lining of reactor.

Defect Engineering on a Ti4O7 Electrode by Ce3+ Doping for the Efficient Electrooxidation of Perfluorooctanesulfonate.

Defect engineering in an electrocatalyst, such as doping, has the potential to significantly enhance its catalytic activity and stability. Herein, we report the use of a defect engineering strategy to enhance the electrochemical reactivity of Ti4O7 through Ce3+ doping (1-3 at. %), resulting in the significantly accelerated interfacial charge transfer and yielding a 37-129% increase in the anodic production of the hydroxyl radical (OH•). The Ce3+-doped Ti4O7 electrodes, [(Ti1-xCex)4O7], also exhibited a more stable electrocatalytic activity than the pristine Ti4O7 electrode so as to facilitate the long-term operation. Furthermore, (Ti1-xCex)4O7 electrodes were also shown to effectively mineralize perfluorooctanesulfonate (PFOS) in electrooxidation processes in both a trace-concentration river water sample and a simulated preconcentration waste stream sample. A 3 at. % dopant amount of Ce3+ resulted in a PFOS oxidation rate 2.4× greater than that of the pristine Ti4O7 electrode. X-ray photoelectron spectroscopy results suggest that Ce3+ doping created surficial oxygen vacancies that may be responsible for the enhanced electrochemical reactivity and stability of the (Ti1-xCex)4O7 electrodes. Results of this study provide insights into the defect engineering strategy for boosting the electrochemical performance of the Ti4O7 electrode with a robust reactivity and stability.

One-step fabrication of oxygen vacancy-enriched Fe@Ti/C composite for highly efficient degradation of organic pollutants through persulfate activation.

In this work, cost-effective, magnetic carbon-supported Fe@Ti composite (Fe@Ti/Cs) with abundant active sites was synthesized by one-step carbothermal reduction of ilmenite with the assistance of microwave oven and utilized as a highly efficient persulfate (PS) activator for the wastewater purification. The coexistence of Fe0/2+/3+, Ti3+/4+ and oxygen vacancies on Fe@Ti/Cs was found to favor for the electron transfer to PS, which facilitate the generation of reactive oxygen species (ROS). Catalytic experiment results showed that the Fe@Ti/C-4 produced from ilmenite/carbon with a mass ratio of 4:1 exhibited the best catalytic activation performance towards PS for the degradation of Rhodamine B (RhB). Usage of merely 0.12 g/L Fe@Ti/C-4 enabled the removal of 94.01% RhB (200 mg/L) within 30 min in the PS containing system, significantly outperforming ilmenite + PS (29.29%) and carbon + PS (49.91%) systems tested under the same conditions. The physico-chemical properties of the produced Fe@Ti/Cs before and after the reaction were carefully characterized. Radical scavenging experiments and electron paramagnetic resonance (EPR) analysis were carried out to better understand the underlying mechanism. The results indicate that oxygen vacancies in Fe@Ti/C-4 promoted the electron transfer and participated in the transition metal redox cycle to generate ROS in the PS-containing system, which was highly efficient for degrading RhB into small molecules and finally enabling mineralization. This work offers a new perspective for designing highly efficient and stable PS activators with long life derived from natural ore for environmental remediation.

Ultrafast removal of Cu(II) by a novel hierarchically structured faujasite-type zeolite fabricated from lithium silica fume.

Novel hierarchically structured Faujasite Type (FAU) zeolite was fabricated from industrial waste lithium silica fume (LSF) via hydrothermal method without the addition of templates. The FAU zeolites exhibited spherical filler morphology with maximum surface area of 372.8 m2/g, enriched microporosity (0.164 cm3/g), and abundant mesoporosity. Owing to its unique structure, the FAU zeolite allowed ultrafast diffusion and rapid trap of copper ion inside the cages of zeolite crystals, and achieved maximum removal (78.76%) of Cu(II) within the very first 2 min, with adsorption rate constant 5.46-6.27 times greater than that of mesoporous commercial zeolite (CZ) between 15 and 45 °C. The physico-chemical structures of the FAU zeolites were carefully studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier Transform Infrared Spectrometry (FT-IR), surface area analyzer (BET) and X-ray photoelectron spectroscopy (XPS). The maximum qe toward Cu(II) achieved by FAU zeolite (i.e., Z9, S/A of 9) featuring a qe of 94.46 mg/g at 25 °C as per calculated from Langmuir model, which is more than twice amount achieved by CZ (39.15 mg/g). Z9 also showed outstanding selectivity for Cu(II) over various coexisting ions. The saturated Z9 can be regenerated with a mild washing procedure, and the spent zeolite can be reused as effective antibacterial agent. This work proposes a cost-effective and green synthesis route for the hierarchically structured zeolite with high copper selective removal capacity from industrial waste.

Preparation and evaluation of nitrogen-tailored hierarchical meso-/micro-porous activated carbon for CO2 adsorption.

In this study, nitrogen-tailored hierarchical meso-/micro-porous activated carbons were successfully fabricated from cypress sawdust by H3PO4 activation with further nitrogen modification using three kinds of nitrogen source (i.e. nitic acid, urea and melamine). The produced carbons were used as adsorbents for CO2 capture. The physic-chemical properties of the produced carbons were characterized by N2 adsorption-desorption, fourier-transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The effects of pore structure and nitrogen content on CO2 adsorption were investigated. It was found that H3PO4 activation would turn cypress sawdust into mesoporous carbon (AC), nitrogen doping could induce the development of microporosity and also increase the basicity of the carbon framework, which favoured for CO2 adsorption. Among the nitrogen-tailed carbons, HNO3-treated activated carbon (AC-N) showed the highest V mic (0.127 cm3/g), the largest CO2 adsorption capacity (2.8 mmol/g at 273 K, 1 bar) and the best CO2/N2 selectivity as compared to urea and melamine treated ones. The adsorption experiments showed that the presence of microporosity and pyrrolic-N on the carbons were responsible for CO2 adsorption, the oxygen functional groups on AC-N might also contribute to higher CO2 uptake, and the mesoporous structure could favour for the fast mass transfer of CO2. The results of CO2 adsorption heat confirmed the high affinity of the prepared carbons to CO2. This study provides a strategy to produce hierarchical meso-/micro-porous activated carbons with enriched nitrogen functional groups, which favoured for CO2 adsorption.

Facile synthesis of novel 3D flower-like magnetic La@Fe/C composites from ilmenite for efficient phosphate removal from aqueous solution.

In this study, a novel 3D flower-like La@Fe/C magnetic composite was successfully synthesized by carbothermal reduction of ilmenite via microwave radiation. The physico-chemical properties of the composite were investigated. The results showed that La@Fe/C features a 3D flower-like morphology with an S BET and V mic of 114 m2 g-1 and 0.017 cm3 g-1, respectively. Zerovalent iron and metal oxides were detected by XRD and XPS on the surface of the adsorbent, which formed as a result of carbothermal reduction of ilmenite using coconut shell-based carbon followed by the introduction of lanthanum. This resultant magnetic La@Fe/C exhibited remarkable phosphate selectivity performance even in the presence of a 50-fold excess of competing ions, which is superior to the pristine ilmenite and coconut activated carbon. Adsorption isotherms and adsorption kinetics fitted well with the Langmuir model and pseudo-second-order model, respectively. A thermodynamic study indicated that the adsorption of phosphate was spontaneous and endothermic. The adsorption-regeneration cyclic experiments of the La@Fe/C composite demonstrated a good level of recyclability. These results indicated that carbothermal reduction of ilmenite followed by the introduction of lanthanum could result in highly efficient and recoverable magnetic particles for the removal of phosphate from wastewater.

A novel mesoporous zeolite-activated carbon composite as an effective adsorbent for removal of ammonia-nitrogen and methylene blue from aqueous solution.

A mesoporous zeolite-activated carbon composite (Z-AC) was prepared by hydrothermal synthesis method for both ammonia-nitrogen (NH3-N) and methylene blue (MB) removal from aqueous solution. For Z-AC with the reparation temperature of 90 °C and kaolin/AC = 4, the adsorption capacity of MB (754.75 mg/g, 298 K) was 83% of that for pure AC, and the adsorption capacity of NH3-N were 9.00 mg/g, which was higher than that for AC and Z (the kaolin after hydrothermal treatment). The Z-AC exhibited obvious mesoporous structure, the SBET of the Z-AC (378 cm2/g) was 31% of that for AC (1215 cm2/g). The introduction of a small amount of AC into Z increased the SBET of Z, thus, the adsorption capacity of MB was improved dramatically. On the other hand, the dispersion of Z was enhanced by adding AC, which promoted the contact between Z and NH3-N, and then led to improvement of the NH3-N adsorption.

A reactive electrochemical filter system with an excellent penetration flux porous Ti/SnO2-Sb filter for efficient contaminant removal from water.

Tubular porous Ti/SnO2-Sb filters with excellent penetration flux (∼61.94 m3 m-2 h-1 bar-1) and electrochemical activity were prepared by a sol-gel method using low-cost porous titanium filters as the substrates. The porous Ti/SnO2-Sb filters were used as anodic reactive electrochemical membranes to develop reactive electrochemical filter systems, by combining membrane filtration technology with the electrooxidation process, for water treatment. A convection-enhanced rate constant of 4.35 × 10-4 m s-1 was achieved for Fe(CN)6 4- oxidation, which approached the kinetic limit and is the highest reported in an electrochemical system. The electrooxidative performance of the reactive electrochemical filter system was evaluated with 50 mg L-1 rhodamine B (RhB). The results showed that the reactive electrochemical filter system in flow-through mode resulted in an 8.6-fold enhancement in RhB oxidation as compared to those in flow-by mode under the same experimental conditions. A normalized rate constant of 5.76 × 10-4 m s-1 for RhB oxidation was observed at an anode potential of 3.04 V vs. SCE, which is much higher than that observed in a reactive electrochemical filter system with carbon nanotubes and/or Ti4O7 (1.7 × 10-5-1.4 × 10-4 m s-1). The electrical energy per order degradation (EE/O) for RhB was as low as 0.28 kW h m-3 in flow-through mode, with a relatively short residence time of 9.8 min. The overall mineralization current efficiency (MCE) was calculated to be 83.6% with ∼99% RhB removal and ∼51% TOC removal. These results illustrate that this reactive electrochemical filter system is expected to be a promising method for water treatment.

The importance of surface functional groups in the adsorption of copper onto walnut shell derived activated carbon.

In this study, activated carbon (AC) was prepared from walnut shell using chemical activation. The surface chemistry of the prepared AC was modified by introducing or blocking certain functional groups, and the role of the different functional groups involved in the copper uptake was investigated. The structural and chemical heterogeneity of the produced carbons are characterized by Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, Boehm titration method and N2/77 K adsorption isotherm analysis. The equilibrium and the kinetics of copper adsorption onto AC were studied. The results demonstrated that the functional groups on AC played an important role in copper uptake. Among various surface functional groups, the oxygen-containing group was found to play a critical role in the copper uptake, and oxidation is the most effective way to improve Cu (II) adsorption onto AC. Ion-exchange was identified to be the dominant mechanism in the copper uptake by AC. Some other types of interactions, like complexation, were also proven to be involved in the adsorption process, while physical force was found to play a small role in the copper uptake. The regeneration of copper-loaded AC and the recovery of copper were also studied to evaluate the reusability of the oxidized AC.

Preparation of activated carbon from corn cob and its adsorption behavior on Cr(VI) removal.

Operation experiments were conducted to optimize the preparation of activated carbons from corn cob. The Cr(VI) adsorption capacity of the produced activated carbons was also evaluated. The impact of the adsorbent dosage, contact time, initial solution pH and temperature was studied. The results showed that the produced corn cob activated carbon had a good Cr(VI) adsorptive capacity; the theoretical maximum adsorption was 34.48 mg g(-1) at 298 K. The Brunauer-Emmett-Teller and iodine adsorption value of the produced activated carbon could be 924.9 m(2) g(-1) and 1,188 mg g(-1), respectively. Under the initial Cr(VI) concentration of 10 mg L(-1) and the original solution pH of 5.8, an adsorption equilibrium was reached after 4 h, and Cr(VI) removal rate was from 78.9 to 100% with an adsorbent's dosage increased from 0.5 to 0.7 g L(-1). The kinetics and equilibrium data agreed well with the pseudo-second-order kinetics model and the Langmuir isotherm model. The equilibrium adsorption capacity improved with the increment of the temperature.

Study on an effective industrial waste-based adsorbent for the adsorptive removal of phosphorus from wastewater: equilibrium and kinetics studies.

In this work, an effective adsorbent for removing phosphate from aqueous solution was developed from modifying industrial waste--lithium silica fume (LSF). The characterization of LSF before and after modification was investigated using an N2 adsorption-desorption technique (Brunauer-Emmett-Teller, BET), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Studies were conducted to investigate the effect of adsorbent dose, initial solution pH, contact time, phosphate concentration, and temperature on phosphate removal using this novel adsorbent. The specific surface area for modified LSF (LLSF) is 24.4024 m(2)/g, improved 69.8% compared with unmodified LSF. XRD result suggests that the lanthanum phosphate complex was formed on the surface of LLSF. The maximum phosphate adsorption capacity was 24.096 mg P/g for LLSF, and phosphate removal was favored in the pH range of 3-8. The kinetic data fitted pseudo-second-order kinetic equation, intra-particle diffusion was not the only rate controlling step. The adsorption isotherm results illustrated that the Langmuir model provided the best fit for the equilibrium data. The change in free energy (△G(0)), enthalpy (△H(0)) and entropy (△S(0)) revealed that the adsorption of phosphate on LLSF was spontaneous and endothermic. It was concluded that by modifying with lanthanum, LSF can be turned to be a highly efficient adsorbent in phosphate removal.