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When fluoride levels in water exceed permitted limits (>1.5 mg L−1), water pollution becomes a major concern to humans.

Electrochemical deionization (EDI) is hopefully the next generation of water treatment technology. Bismuth (Bi) is a promising anode material for EDI, due to its high capacity and selectivity toward Cl

Fluoride concentration in drinking water has become a global challenge due to its effects on the human body. While small level (1–1.5 mg·L−1) strengthens enamel and bone formation, higher concentra...

Metal-organic frameworks (MOFs) based membranes with superior mechanical properties are of particular interest in purification, separation, and catalysis. Nevertheless, their fabrication still remains a grand challenge. Here, fungus hyphae (Mucor) were used as a robust scaffold to load the MOFs and induced the formation of porous and flexible membranes. ZIF-8 was used as a representative of MOFs. The ZIF-8@Mucor membrane was formed by the in-situ growth of ZIF-8 on hyphae and then a vacuum filtration of the ZIF-8/hyphae composite. ZIF-8 was effectively dispersed on the ZIF-8@Mucor membrane, and the shear modulus of ZIF-8@Mucor-3 was 864 MPa by calculation. The ZIF-8@Mucor membrane exhibited promising properties for adsorption application to remove the highly toxic Pb2+. The adsorption capacity of this membrane was as high as 1443.29 mg/g. Results from dynamic adsorption indicated that the penetration concentration of Pb2+ ions was less than 5% of the original level before 80 min whereas after 160 min, penetration concentration of Pb2+ ions was more than 90%. This study would open a new way of how to synthesize composite MOFs/bacterial membranes for energy and environment purposes.

Capacitive deionization (CDI) by Ag@C electrodes is a promising desalination technology for chlorine removal because there is no waste flow and no additional chemicals used during the removal and regeneration/cleaning processes. However, its efficacy and capacity are significantly limited by the low stability of Ag/C composites during the electrochemical process. In this study, we synthesized a new highly stable structure of Ag@C composites (named as Ag/N-CNP) through reductive adsorption of Ag+ by a polyaromatic amine followed by carbonization. We used in situ Raman spectroscopy, for the first time, to monitor in real-time the Cl− electrosorption/desorption process of Ag/N-CNP electrodes, which revealed that the stability of Ag@C electrodes was mainly controlled by the dissolution of Ag. The newly synthesized Ag–Nx structure stabilized Ag nanoparticles and uniformly distributed Ag species on the carbon matrix, which resulted in a high affinity for Cl− and significantly improved cyclic dechlorination performance. Results showed that the electrosorption capacity of the newly synthesized Ag/N-CNP electrodes could reach 75.3 mg g−1, substantially higher than that of traditional carbon electrodes. Moreover, such a capacity had almost no loss (only 1.4% loss) after 50 continuous treatment cycles and could still retain 76% after 100 cycles, demonstrating a highly reliable and cost-effective desalination performance significantly superior to that of previously reported Ag@C electrodes.

Bauxite is a widely available Al-O-rich mineral with great potential for abating fluoride. However, low adsorption capacity, a narrow workable pH range, and a lack of clarity on the best removal mechanism hinder its application. In this work, a highly efficient bauxite nanocomposite (Bx-Ce-La@500) was synthesized via doping and pyrolysis, and its fluoride adsorption in industrial wastewater was examined. Doping Ce/La synergistically improved the fluoride adsorption affinity of the composite (from pH

Electrostatic and complexation effects have been considered as the primary adsorption mechanisms for defluorination using aluminum based materials, while the effect of ion exchange between anions and fluorine ion has been mostly ignored, although synthesized alumina materials usually contain a large amount of anions, such as SO

The surface properties of arsenopyrite during chemical and biological oxidation were investigated by synchrotron X-ray diffraction (S-XRD), X-ray absorption near-edge structure (XANES) and scanning electron microscope (SEM), accompanying with leaching behaviors elucidation. The moderate thermophile S. thermosulfidooxdians was used as the bioleaching microorganism. Leaching experiments showed that only 16.26% and 44.37% of total arsenic extractions were obtained for sterile acid and culture medium controls, whereas 79.20% of total arsenic was recovered at the end of bioleaching. SEM indicated that new products were layered on the surface of arsenopyrite after chemical and biological oxidation. As displayed in S-XRD patterns, scorodite and elemental sulfur were formed after acid leaching, while only elemental sulfur was detected in the residue leached by acid culture medium. During bioleaching, elemental sulfur was produced from day 4 and jarosite was produced from day 9. The results of iron and arsenic L-edge XANES were in good consistence with S-XRD. The accumulation of scorodite and jarosite on arsenopyrite surface should be the main reason for the hindered dissolution of arsenopyrite during acid leaching and bioleaching. These studies are pretty meaningful for better understanding the oxidation mechanism of arsenopyrite and evaluating arsenic risk to the environment.

N dopping can enhance the electrochemical efficiency of carbon materials, but the effect of N on the electrochemical-mediated removal of Cr(VI) has been mostly ignored. Here, we report highly porous N-doped carbon spheres for electrochemical-mediated removal of Cr(VI), and the role of N on Cr(VI) removal has been systematically investigated using both experimental evaluations and theoretical validation. Experimental findings revealed that the removal capacity of Cr(VI) reached 186.5 mg·g−1 with a removal rate of 100%. In addition, the underlying processes for the role of N species have been investigated using density functional theory (DFT) calculations. The result agrees with the findings from the experimental evaluations thus suggesting that the removal process of Cr(VI) was mainly distributed by pyridinic-N and oxidized-N. This study has demonstrated that the removal of Cr(VI) by N species forms a crucial part in the removal of Cr(VI) using N-doped carbon materials and offers a possible alternative approach for enhancing the removal efficiency of carbon materials.

Electrostatic and complexation effects have been considered as the primary adsorption mechanisms for defluorination using aluminum based materials, while the effect of ion exchange between anions and fluorine ion has been mostly ignored, although synthesized alumina materials usually contain a large amount of anions, such as SO42−, NO3−, and Cl−. In this study, the effect of anions exchanges and its key role on defluorination were systematically investigated for adsorption by aluminas loaded with various typical anions (SO42−, NO3− and Cl−). Experimental results showed that SO42-- loading alumina had the best defluorination performance (94.5 mg/g), much higher than NO3− (45.0 mg/g) and Cl− (19.1 mg/g). The contribution ratio of ion exchange between SO42− and F− was as high as 20–60% in all potential defluorination mechanisms. By using Density Functional Theory calculation, the detailed mechanism revealed that the ion exchange process was mainly driven by the tridentate chelation of SO42− which reduced the exchange energy ( Δ F − − SO 4 2 − 4.8 eV). Our study clearly demonstrated that ion exchange between SO42− and F− is a critical mechanism in defluorination using aluminum-based materials and provides a potential alternative method to enhance the adsorption performance of modified alumina.

Metal-organic frameworks (MOFs) based membranes with superior mechanical properties are of particular interest in purification, separation, and catalysis. Nevertheless, their fabrication still remains a grand challenge. Here, fungus hyphae (Mucor) were used as a robust scaffold to load the MOFs and induced the formation of porous and flexible membranes. ZIF-8 was used as a representative of MOFs. The ZIF-8@Mucor membrane was formed by the in-situ growth of ZIF-8 on hyphae and then a vacuum filtration of the ZIF-8/hyphae composite. ZIF-8 was effectively dispersed on the ZIF-8@Mucor membrane, and the shear modulus of ZIF-8@Mucor-3 was 864 MPa by calculation. The ZIF-8@Mucor membrane exhibited promising properties for adsorption application to remove the highly toxic Pb

Fluoride has been reported as one of the major water pollutants with myriads of health implications when present in water beyond permissible limits (>1.5 mg L−1). While the adsorption technology of treating fluoridated water remains one of the best options, the choice of suitable adsorbent remains a problem. However, shortcomings of some adsorbents such as low adsorption capacity, slow adsorption rate, narrow pH range, and high-cost make them unsustainable. Modification of adsorbents has become the most attractive method for effectively improving the treatment of fluoridated water. The objective of this work was to bring to light the surface modifications and sorption mechanisms of bauxite as a sorbent for fluoride removal. Bauxite is robust with sufficient mechanical strength and naturally abundant making it a suitable candidate over other conventional adsorbents for fluoride removal. Four main types of surface modification of adsorbents were identified; thermal activation, impregnation, functionalization, and chemical grafting. Materials such as surfactants, oxidizing agents, acids, bases, and metals could be used for surface modification. Modified bauxite demonstrated higher adsorption capacity over their unmodified ones due to the significant improvement in their surface area, pore size, pore-volume, and some structural transformations such as ordered and stable interlinked mesopores which facilitated effective chemisorption. This guarantees a stable chemical structure with more active sites and requires a minimum dose to reach equilibrium at a wider pH range (3–11). Finally, the mechanisms of fluoride sorption onto bauxite is a complex process involving intra-particle diffusion, physisorption, and chemisorption processes.

Ammonium dibutyl dithiophosphate (ADD) is one of the most important flotation reagents in sulfide mineral processing, causing severe environmental pollution. In this study, natural pyrrhotite (NP)-activated peroxydisulfate (PDS) was applied to treat ADD, which can alleviate mine tailing problems and reduce the cost of treating mine wastewater. PDS can be efficiently activated by NP for ADD degradation, achieving complete ADD removal with 0.35 g/L NP and 1.0 mM PDS. The PDS activation not only occurred in solution but on the NP surface. Dissolved Fe2+, dissolved Fe3+, surface-bound Fe2+, and surface-bound Fe3+ had been undergoing interconversion as the degradation reaction proceed. The generated sulfate radicals and hydroxyl radicals synergistically remove ADD in the NP/PDS system over a wide pH range. The excess O2 might cause the transformation of S O 4 ∙ - to S O 3 ∙ - in the NP/PDS/ADD system. Based on the density functional theory (DFT) calculation and the identification of intermediates, a pathway of ADD degradation in the NP/PDS system is proposed.

Heteroatoms doping is an important modification method in carbon electrode for CDI technology. In this study, a new facile approach of homogeneous phosphorus doping in carbon matrix was proposed via crosslinking polymerization of m-phenylenediamine and phytic acid. The carbonized composites (NPC) showed the characteristics of phosphorus/nitrogen co-doping with excellent hydrophilicity, high electrochemical performance, lower inner resistance and good cycling stability, far beyond that of carbon without phosphorus doping. Compared with reported similar materials and commercial carbon, the chloride adsorption capacity of NPC used as electrode for deionization capacitors was significantly improved (21.4 mg g−1 in a 500 mg L−1 Cl− solution at 1.2 V). Particularly, based on the charge distribution analysis of phosphorus doping in carbon matrix by using Material Studio calculation, the possible enhanced dichlorination mechanism of the carbon composites as electrode for deionization capacitors was carefully explored. The phosphorus/nitrogen co-doped carbon displayed a promising prospect for chloride removal in the application of CDI technology.

Natural pyrrhotite (NP) shows promising future in activating persulfate (PS) due to its easy availability at a low cost and easy separation. This study discussed the degradation of O-isopropyl-N-ethyl thionocarbamate (IPETC) in NP/PS system. NP-PS system showed the best IPETC mineralization at the initial pH of 6.0 (62.84%). The kinetics study suggested that the IPETC degradation followed the pseudo-first-order equation in the NP-PS system. NP-PS system worked better in bottled water (96.46%) and tap water (85.14%) than river water (31.28%). Combined with Fourier transform–infrared spectroscopy, gas chromatography-mass spectrometry and computational calculation, the degradation products, including acetone, formic acid isopropyl ester and ethylamine, were identified and the degradation pathway of IPETC in NP-PS system was proposed. The S, O and N atoms in IPETC are easier to be attacked by. SO4 −Ethylamine and reduced S ions coordinately worked to recycle Fe2+ in NP/PS/IPETC system.