A novel composite electrode with multiple pore structures for efficient treatment of heavy metal ions in capacitive deionization.

Multiple porous carbon materials have great promise and potential in the capacitive deionization (CDI) field. Specific surface area (SSA), pore size distribution, and preparation method of CDI electrode materials are essential for the treatment of heavy metal ions. In this work, PPy composited porous carbon electrodes (hypercrosslinked polymers/polypyrrole, HCPs/PPy) were obtained by one-step crosslinked carbonization preparation and electro-deposition. The diverse pore structure gives the composite electrode a large SSA and excellent adsorption performance. HCPs/PPy-4 gives a high SSA of 251.26 m2/g. In the CDI process, the adsorption capacity of HCPs/PPy-4 for Fe3+, Cu2+, Pb2+, and Ag+ is 20.69 mg/g, 37.81 mg/g, 26.86 mg/g, and 40.95 mg/g. The negative electrode recoveries for the adsorption of the four ions were reached 81.2%, 89.2%, 85.5%, and 100%, respectively. It indicates that HCPs/PPy is a novel and potentially porous carbon electrode for high-performance CDI.

Visible light photocatalytic degradation of oxytetracycline hydrochloride using chitosan-loaded Z-scheme heterostructured material BiOCOOH/O-gC3N4.

In this work, a Z-scheme heterostructured BiOCOOH/O-gC3N4 material was synthesized and immobilized on chitosan (CTS) to obtain the BiOCOOH/O-gC3N4/CTS photocatalytic material for photocatalytic degradation of oxytetracycline hydrochloride (CTC).Our findings indicate that the composite material BiOCOOH/O-gC3N4, as well as the BiOCOOH/O-gC3N4/CTS composite membrane, displayed a significantly higher efficiency in photocatalytic degradation of CTC compared to BiOCOOH alone, owing to the synergistic effect of adsorption and photocatalysis. Following four cycles of use, the composite material retained around 96 % of its initial photocatalytic degradation activity. The addition of CTS in the photocatalytic material resolved issues such as aggregation and difficult recovery commonly encountered with powder materials, thereby facilitating effective collision between the photocatalytic active sites and CTC. Experimental and theoretical calculations provided confirmation that the combination of BiOCOOH and O-gC3N4 effectively enhanced the light absorption capacity and photocatalytic performance. Furthermore, we investigated the influence of environmental factors such as pH value and anions on the photocatalytic degradation experiment, which offers valuable insights for the application of composite catalysts in wastewater treatment.

Preparation and performance of aerogel-based BiOI/TiO2 heterojunction photoelectrocatalytic electrodes.

TiO2/BiOI/CA electrodes with improved conductivity, reduced photoelectron-hole recombination rates, and increased reaction sites based on p-n type heterojunctions were constructed on carbon aerogels (CA) as photoelectrode substrates. Characterization based on ultraviolet-visible diffuse reflectance spectroscopy, photocurrent measurements, and impedance analysis showed that the TiO2/BiOI/CA photoelectrode with a Ti/Bi mole ratio of 0.4 exhibited the best visible light absorption, lowest photogenerated electron-hole pair recombination rate, and strongest photocatalytic degradation, with 90.4% degradation of phenol under 120 min of light. Moreover, the stability of this electrode remained at a high level. This was mainly because the energy levels of TiO2 and BiOI matched each other and the p-n heterojunction formed adjusted the energy band structure of the composite material, widened the electron transfer path, formed an internal electric field between the phase interfaces, had a higher electron transfer rate, and reduced the photogenerated electron-hole recombination rate. Since ˙OH and ˙O2- are the main active substances in the degradation of phenol, the TiO2/BiOI/CA photoelectrodes had higher degradation efficiency than BiOI/CA electrodes. This study provides a unique concept for the treatment of organic pollutant wastewater and electrode design for photoelectrocatalysis.

Selective capacitive removal of Pb2+ ion contaminants from drinking water via nickel foam/Mn2CoO4@tannic acid-Fe3+ electrodes.

The health hazards caused by low concentrations of Pb2+ ions in drinking water systems are of significant concern. In order to remove Pb2+ ions and retain Na+, K+, Ca2+ and Mg2+ as harmless competitive ions without simultaneous removal, nickel foam (NF)/Mn2CoO4@tannic acid (TA)-Fe3+ electrodes were prepared by a hydrothermal method and a coating method and an asymmetric capacitive deionization (CDI) system is established using the prepared electrodes and a graphite paper positive electrode. The designed asymmetric CDI system exhibited a high Pb2+ adsorption capacity of 375 mg g-1 with high removal efficiency and significant regeneration behavior at 1.4 V at neutral pH. When the asymmetric CDI system is used to enrich a hydrous solution of mixed Na+, K+, Ca2+, Mg2+ and Pb2+ ions each with a concentration of 10 ppm and 100 ppm by electrosorption at a 1.4 V operating voltage, the removal rate of Pb2+ is as high as 100% and 70.8% respectively, and the relative selectivity coefficients are 4.51-43.22. According to the different adsorption mechanisms of lead ions and coexisting ions, the separation and recovery of ions can be realized by a two-step desorption process, thereby providing a new method for removing Pb2+ ions from drinking water with excellent application potential.

Electrooxidation degradation of hydroxychloroquine in wastewater using a long-acting Ti-based PbO2 anode with an arc-sprayed (Ti,Zr)N interlayer.

To solve the challenges facing the low-cost and high-efficiency purification of water pollution caused by the production and metabolism of biodegradable hydroxychloroquine (HCQ), electrooxidation treatment with a Ti-based PbO2 anode is the most promising technical solution for engineering applications. However, Ti-based PbO2 anodes have apparent disadvantages, such as poor stability and insufficient electrocatalytic activity. To overcome these shortcomings, a novel Ti/(Ti,Zr)N/PbO2 anode was prepared by introducing an arc-sprayed (Ti,Zr)N conductive composite interlayer together with a PbO2 surface layer anodically deposited at different times on a Ti substrate. The electrocatalytic activity, anode stability, optimized parameters and degradation mechanism of the HCQ electrooxidation treatment were experimentally studied. As a result, compared to the Ti/PbO2 anode without an interlayer, the Ti/(Ti,Zr)N/PbO2 anode not only showed obviously excellent stability but could also effectively electrocatalytically degrade HCQ. The optimal Ti/(Ti,Zr)N/PbO2-2.0 anode prepared using the arc-sprayed (Ti,Zr)N interlayer and electrodepositing PbO2 for 2 h can remove 95.85% of 200 mg L-1 HCQ at 20 °C and pH 7 after electrolysis at 20 mA cm-2 for 3 h, and possesses a longer accelerated life with 11.8 times the lifetime of the Ti/PbO2 anode. Furthermore, after five consecutive periodic electrooxidation treatments, its degradation rate was retained at 86.3% and its Pb2+ dissolution concentration (0.0036 mg L-1) met the requirements of the Chinese standard for drinking water. This long-acting PbO2 coated anode reveals promising application potential for the electrocatalytic degradation of refractory organic sewage, such as HCQ, which will help to promote the practical popularization of electrooxidation water treatment technology.

Visible Light Accelerates Cr(III) Release and Oxidation in Cr-Fe Chromite Residues: An Overlooked Risk of Cr(VI) Reoccurrence.

The reduced chromite ore processing residue (rCOPR) deposited in environments is susceptible to surrounding factors and causes reoccurrence of Cr(VI). However, the impact of natural sunlight on the stability of rCOPR is still unexplored. Herein, we investigated the dissolution and transformation behaviors of Cr(III)-Fe(III) hydroxide, a typical Cr(III)-containing component in rCOPR, under visible light. At acidic conditions, the release rate of Cr(III) under illumination markedly increased, up to 7 times higher than that in the dark, yet no Cr(VI) was produced. While at basic conditions, only Cr(VI) was obtained by photo-oxidation, with an oxidation rate of ∼7 times higher than that by δ-MnO2 under dark conditions at pH 10, but no reactive oxygen species was generated. X-ray absorption near-edge structure and density functional theory analyses reveal that coexisting Fe in the solid plays a critical role in the pH-dependent release and transformation of Cr(III), where photogenerated Fe(II) accelerates Cr(III) produced at acidic conditions. Meanwhile, at basic conditions, the production of intermediate Cr(III)-Fe(III) clusters by light leads to the oxidation of Cr(III) into Cr(VI) through the nonradical "metal-to-metal charge transfer" mechanism. Our study provides a new insight into Cr(VI) reoccurrence in rCOPR and helps in predicting its environmental risk in nature.

Vis-UV Upconverting bacteriostatic hydrophobic bacterial cellulose film for personal protective masks.

Masks are key to personal protection and their bacteriostatic properties, which are generally overlooked, should be maximized. Towards this goal, a YPS-Pr-Li/BC upconversion antibacterial composite film was prepared by mixing upconversion powder with bacterial cellulose (BC) using a vacuum assisted method. When combined with the low surface energy of stearic acid (STA), the resulting YPS-Pr-Li/BC/STA film had an improved hydrophobic surface. The developed film was characterized by FT-IR, SEM, XRD, and fluorescence spectrophotometry. The results showed that the composite film was successfully prepared and had ultraviolet, visible upconversion luminescence. The bacteriostatic experiments showed that the material had excellent bacteriostatic performance against E. coli and S. aureus under visible light, with a bacteriostatic rate reaching 99 %. The in-vitro cytotoxicity tests showed that YPS-Pr-Li/BC/STA had excellent biocompatibility and could be used in personal protective clothing with close contact with human skin.

Efficient degradation of VOCs using semi-coke activated carbon loaded ternary Z-scheme heterojunction photocatalyst BiVO4-BiPO4-g-C3N4 under visible light irradiation.

The coal chemical industry generates large amounts of solid waste and volatile organic compounds (VOCs). In this study, the solid waste semi-coke powder obtained in the semi-coke production process was used as a raw material to prepare high-specific surface area semi-coke activated carbon (SAC) by a carbonization and activation process, and a ternary z-scheme heterojunction photocatalyst with high catalytic performance was loaded for synergistic treatment by adsorption and photodegradation to achieve waste treatment with waste. The prepared semi-coke activated carbon has a specific surface area of 619.27 m2 g-1, which can achieve effective adsorption of VOCs. The ternary z-scheme heterojunction photocatalyst BiPO4-BiVO4-g-C3N4 (PVCN) was supported on a semi-coke activated carbon substrate by a one-step sol-gel method. Based on the synergistic effect of adsorption and photocatalysis, the obtained PVCN/SAC material can degrade toluene by 85.6% within 130 minutes under simulated sunlight irradiation, which is 2.43 times that of pure photocatalyst. The rate of degrading toluene can be increased by 4.43 times. Capture experiments showed that superoxide radicals (˙O2-) and hydroxyl radicals (˙OH) were the key active species in the degradation pathway. Even after five cycles, the material maintained 81.6% of the degradation performance. In this work, we deeply investigate the mechanism of semi-coke activated carbon as a matrix for enhancing photocatalytic degradation performance. The findings of this work provide new insights into the efficient degradation of VOCs and provide a good theoretical basis for the development of high-performance photocatalysts.

Photocatalytic degradation of dye wastewater by stepwise assembling PVA aerogel/TiO2/MoS2/Au composites in visible light.

A PVA aerogel/TiO2/MoS2/Au catalyst formed gradually using a hydrothermal method is used to degrade Rhodamine B. SEM and TEM results show that the composite presents a uniform and well-structured porous network structure, high specific surface area and large pore diameter were proved by the results of nitrogen adsorption measurement. UV-vis DRS and PL results indicate that the composite has a high absorption rate in the visible light range, and the recombination of photogenerated electron-hole pairs can be effectively inhibited because the composite material forms a heterojunction. In the photocatalytic degradation experiment of Rhodamine B, the composite material shows high photocatalytic performance, which can reach 86% in two hours of light. The photocatalysts supported by PVA are easy to recover and have high catalytic performance even after five recycles. The study shows that PVA/TiO2/MoS2/Au composite material has great potential to be used for the degradation of dye wastewater.

Bacteriostatic activity and cytotoxicity of bacterial cellulose-chitosan film loaded with in-situ synthesized silver nanoparticles.

Bacterial infections on open wounds have always been a threat to human health. Herein, we prepared a silver (Ag)-polydopamine (PDA)/bacterial cellulose (BC)-chitosan (CTS) film using biological self-generation and in situ reduction. CTS was added to culture medium to allow BC to intertwine with CTS during film formation. Silver nitrate was reduced in situ to Ag nanoparticles under ultraviolet irradiation, and the nanoparticles were well dispersed in the BC-CTS film with the help of PDA, which worked synergistically with the CTS. The Ag-PDA/BC-CTS film was enriched in functional groups, and it had good tensile and swelling properties. The inhibition film demonstrated broad-spectrum inhibition of Gram-positive and Gram-negative bacteria, and this inhibition was maintained at more than 80% after 48 h of continuous use. The good biocompatibility of the film was verified using NIH3T3 fibroblasts. The results suggested that the Ag-PDA/BC-CTS film inhibited the growth of harmful bacteria while having little effect on healthy cells.

A RGO aerogel/TiO2/MoS2 composite photocatalyst for the removal of organic dyes by the cooperative action of adsorption and photocatalysis.

A composite consisting of reduced graphene oxide aerogel/titanium dioxide/molybdenum disulfide (abbreviated as RGO aerogel/TiO2/MoS2) was developed for the removal of organic dyes from solution cooperatively by adsorption and photocatalytic degradation mechanisms. The composite was successfully synthesized by stepwise layered assembly integration, including sol-gel and physical vapor deposition (PVD) methods. The resulting multi-component composite material featured a high specific surface area (255.441 m2/g) containing a myriad of negatively charged carboxylate functional groups on the surface of the composite, which enabled the composite material to demonstrate a high removal efficiency of cationic dyes, such as rhodamine B, from solution. In addition, the composite featured optimal optical and photocatalytic properties for facilitating efficient photodegradation of the dye molecules, including a large absorbance in the visible light region and a fast transfer of photogenerated electron-hole pairs. Moreover, electron paramagnetic resonance (EPR) analysis and reactive oxygen species scavenging experiments confirmed that superoxide radicals (O2•-), holes (h+), and hydroxyl radicals (•OH) were involved in photocatalytic degradation of the organic dyes.

CaCO3-coated PVA/BC-based composite for the simultaneous adsorption of Cu(II), Cd(II), Pb(II) in aqueous solution.

A polymer composite material comprising polyvinyl alcohol/bacterial cellulose/calcium carbonate (PVA/BC/CaCO3) was prepared for enabling the selective adsorption of toxic heavy metal ions, such as Cd(II), Cu(II), and Pb(II) from solution. FT-IR, SEM and XRD analyses confirmed the successful incorporation of CaCO3 into the PVA-based polymer by chemical cross-linking with epichlorohydrin. The optimal pH for adsorption of the metal ions onto PVA/BC/CaCO3 was determined to be 6.0. The pseudo-first-order kinetics model was best-suited for fitting the adsorption kinetics data, and the Langmuir model was best-suited for fitting the thermodynamic adsorption data. The maximum adsorption capacities of PVA/BC/CaCO3 for Cu(II), Pb(II), and Cd(II) were found to be 57.1, 513.6, and 238.6 mg/g, respectively, at 40 °C. In addition, the adsorbent was found to be highly recyclable. Overall, PVA/BC/CaCO3 adsorbent has the applicable potential in the removal of heavy metal ions from contaminated solution.

Preparation and bacteriostatic research of porous polyvinyl alcohol / biochar / nanosilver polymer gel for drinking water treatment.

Microbial contamination in drinking water has become an important threat to human health. There is thus an urgent need to develop antibacterial materials to treat drinking water. Here, porous silver-loaded biochar (C-Ag) was prepared using corn straw as the substrate and silver as the antibacterial agent. C-Ag was then uniformly distributed in polyvinyl alcohol gel beads of eluted calcium carbonate to prepare p-PVA/C-Ag antibacterial composite. The polymer composites were tested by FT-IR, XRD, SEM and TG-DSC. The results showed that C-Ag was more evenly distributed in the PVA gel spheres. Antibacterial experiments showed that p-PVA/C-Ag greatly inhibited Escherichia coli. Practical application tests revealed that p-PVA/C-Ag showed high and sustained bactericidal inhibition and reusability. Generally, p-PVA/C-Ag composite shows high potential to be applied to drinking water treatment.

Preparation and properties of conductive bacterial cellulose-based graphene oxide-silver nanoparticles antibacterial dressing.

It is difficult to obtain stable multifunctional silver-containing materials that are suitable for use as wound dressings. To solve this problem, we added graphene oxide (GO) to an acetobacter culture medium and used a biological blending self-growth method to fix GO onto the bacterial cellulose to form a mixed-growth film. We then used polydopamine to fix AgNPs to obtain a novel silver-based cellulose wound dressing. This composite material was characterized by infrared spectroscopy, electron microscopy, and X-ray diffractometry, and the results showed that silver nanoparticles uniformly covered the material surface, while graphene was wrapped in a layer of bacterial cellulose. This composite film was conductive and produced a weak current, and it generated heat when a voltage was applied. This allowed it to accelerate wound cell migration and promote wound healing. In addition, AgNPs immobilized on the surface released Ag+, which generated a large number of oxidizing free radicals that killed and bacteria. The in vitro cytotoxicity tests showed that the Ag-pDA/BC (rGO) composite film has excellent biocompatibility, giving it good application prospects for wound dressings.

Preparation of a Polypyrrole/Graphene Oxide Composite Electrode by Electrochemical Codeposition for Capacitor Deionization.

In this paper, a polypyrrole/graphene oxide (PPy/GO) composite electrode, applied to the capacitive deionization process for removing heavy metal ions, was prepared by one-step electrochemical codeposition. The PPy/GO composite electrode has a dense sheet structure, and PPy is spherical and uniformly distributed on the surface of GO sheets. The experimental results show that the PPy/GO composite electrode has a higher capacitance (186.67 F/g) and a lower charge transfer resistance (1.626 Ω·cm2) than the PPy electrode. The adsorption capacity of the PPy/GO composite electrode is 41.51 mg/g, which is about 2.67 times (15.52 mg/g) that of the PPy electrode. After five adsorption/desorption treatments, the adsorption capacity was maintained at about 98.0%, and the regeneration rate was 94.7%. Therefore, the electrode has good cycle stability and regenerability. In addition, the adsorption capacity of different metal ions follows the order Ag+ < Cd2+ < Cu2+ < Pb2+ < Fe3+, indicating that the PPy/GO composite electrode has stronger adsorption capacity for the added state, and the adsorption capacity for ions with the same valence state decreases with the increase in ion hydration radius. The PPy/GO composite electrode has a good prospect for the removal of heavy metal ions in industrial wastewater.

Preparation of an antibacterial chitosan-coated biochar-nanosilver composite for drinking water purification.

Microbial contamination has evolved as a life-threatening problem afflicting people due to various diseases caused by pathogenic bacteria in drinking water. Thus developing novel antibacterial materials is an urgent need. Herein, a chitosan (CTS)/ biochar-nanosilver (C-Ag) antibacterial composite was prepared by a method of CTS-coated on C-Ag obtained through a facile high-temperature carbonization process using corn straw as the carbon substrate. The results from FT-IR, XRD, SEM and TG-DSC revealed that the biochar loading spherical silver nanoparticles was coated with CTS in the composite. The antibacterial activity of the CTS/C-Ag composite was investigated using the plate counting method with Escherichia coli (E. coli), and the results suggest that the composite exhibited excellent antibacterial activity against E. coli. In this application study, it was proven that the CTS/C-Ag composite exhibits sustainable antibacterial activity and good reusability for drinking water. Therefore, the CTS/C-Ag composite has potential application in drinking water treatment.

Recycling of Cr (VI) from weak alkaline aqueous media using a chitosan/ triethanolamine/Cu (II) composite adsorbent.

A Chitosan/triethanolamine/Cu (Ⅱ) (CTS/TEA/Cu (Ⅱ)) composite adsorbent was prepared and applied to recycle Cr (Ⅵ) from aqueous media in alkaline conditions. To investigate the adsorption behavior, the influence of pH was evaluated via batch experiments, and the prepared adsorbent was characterized by FT-IR, SEM, XRD, and Zeta potential. This adsorbent exhibited high adsorption capacity for Cr (Ⅵ) in a wide pH range (especially above 7), suggesting a possible way to separate Cr (Ⅵ) from other metal cations by adjusting the pH value prior to adsorption. Adsorption kinetic and thermodynamic experiments were conducted to explore the adsorption mechanism. Regeneration studies showed that the adsorbent can be reused for five adsorption-desorption cycles without substantial loss of adsorption capacity. Overall, the CTS/TEA/Cu (Ⅱ) adsorbent exhibits high potential for recyclingCr (Ⅵ) from wastewater.

Hydrothermal synthesis of Bi2WO6 with a new tungsten source and enhanced photocatalytic activity of Bi2WO6 hybridized with C3N4.

Bi2WO6 nanosheets were synthesized by a hydrothermal method with H2WO4 for the first time. The band structure of Bi2WO6 was investigated on the basis of density functional theory calculations. Bi2WO6 photocatalysts showed photocatalytic activity for the degradation of methylene blue under visible light irradiation. Kinetic studies using radical scavenger technologies suggested that holes were the dominant photo-oxidants. After hybridization with C3N4, the photocatalytic activity of Bi2WO6 was obviously enhanced. The enhanced photocatalytic activity of the C3N4/Bi2WO6 photocatalysts could be attributed to the effective separation of photogenerated e-/h+ pairs. The photogenerated holes on the valence band of Bi2WO6 can transfer to the highest occupied molecular orbital of C3N4via the well-developed interface, causing a reduction in the probability of e-/h+ recombination; consequently, large numbers of photogenerated holes led to the enhancement of the photocatalytic activity.

A two-step approach for copper and nickel extracting and recovering by emulsion liquid membrane.

The recycling of copper and nickel from metallurgical wastewater using emulsion liquid membrane (ELM) was studied. P507 (2-ethylhexyl phosphonic acid-2-ethylhexyl ester) and TBP (tributyl phosphate) were used as carriers for the extraction of copper and nickel by ELMs, respectively. The influence of four emulsion composition variables, namely, the internal phase volume fraction (ϕ), surfactant concentration (Wsurf), internal phase stripping acid concentration (Cio) and the carrier concentration (Cc), and the process variable treat ratio on the extraction efficiencies of copper or nickel were studied. Under the optimum conditions, 98% copper and nickel were recycled by using ELM. The results indicated that ELM extraction is a promising industrial application technology to retrieve valuable metals in low concentration metallurgical wastewater.

Treatment of cyanide wastewater by bulk liquid membrane using tricaprylamine as a carrier.

The transport of cyanide from wastewater through a bulk liquid membrane (BLM) containing tricaprylamine (TOA) as a carrier was studied. The effect of cyanide concentration in the feed solution, TOA concentration in the organic phase, the stirring speed, NaOH concentration in the stripping solution and temperature on cyanide transport was determined through BLM. Mass transfer of cyanide through BLM was analyzed by following the kinetic laws of two consecutive irreversible first-order reactions, and the kinetic parameters (k(1), k(2), R(m)(max), t(max), J(a)(max), J(d)(max)) were also calculated. Apparently, increase in membrane entrance (k(1)) and exit rate (k(2)) constants was accompanied by a rise in temperature. The values of activation energies were obtained as 35.6 kJ/mol and 18.2 kJ/mol for removal and recovery, respectively. These values showed that both removal and recovery steps in cyanide transport is controlled by the rate of the chemical complexation reaction. The optimal reaction conditions were determined by BLM using trioctylamine as the carrier: feed phase: pH 4, carrier TOA possession ratio in organic phase: 2% (V/V), stripping phase concentration of NaOH: 1% (W/V), reaction time: 60 min, stirring speed: 250 r/min. Under the above conditions, the removal rate was up to 92.96%. The experiments demonstrated that TOA was a good carrier for cyanide transport through BLM in this study.