A highly sensitive, long-time stable Ag/AgCl ultra-micro sensor for in situ monitoring chloride ions inside the crevice using SECM.

Tracking the variation of Cl- timely within the crevice is of great significance for comprehending the dynamic mechanism of crevice corrosion. The reported chloride ion selective electrodes are difficult to realize the long-time Cl- detection inside the confined crevice, due to their millimeter size or a relative limited lifespan. For this purpose, an Ag/AgCl ultra-micro sensor (UMS) with a radius of 12.5 µm was fabricated and optimized using laser drawing and electrodeposition techniques. Results show the AgCl film's structure is significantly impacted by the deposited current density, and further affects the linear response, life span and stability of Ag/AgCl UMS. The UMS prepared at current density of 0.1 mA/cm2 for 2 h shows a rapid response (several seconds), excellent stability and reproducibility, strong acid/alkali tolerance, sufficient linearity (R2 > 0.99), and long lifespan (86 days). Moreover, combined with the potentiometric mode of scanning electrochemical microscope (SECM), the Ag/AgCl UMS was successfully applied to monitor the in-situ radial Cl- concentration in micro-regions inside a 100 µm gap of stainless steel. The findings demonstrated that there was obvious radial difference in Cl- concentration inside the crevice, where the fastest rise in Cl- concentration was at the opening. The proposed method which combines the UMS with SECM has attractive practical applications for microzone Cl- monitoring in real time inside crevice. It may further promote the study of other localized corrosion mechanism and the development of microzone ions detection method.

Crevice Corrosion Behavior of 201 Stainless Steel in NaCl Solutions with Different pH Values by In Situ Monitoring.

Crevice corrosion (CC) behavior of 201 stainless steel (SS) in 1 M NaCl + x M HCl/y M NaOH solutions with various pH was investigated using SECM and optical microscopic observations. Results show that the CC was initiated by the decrease in pH value within the crevice. The pH value near the crevice mouth falls rapidly to 1.38 in the first 2 h in the strongly acidic solution, while the pH value was observed to rise firstly and then decrease in the neutral and alkaline solutions. It indicates there is no incubation phase in the CC evolution of 201-SS in a pH = 2.00 solution, while an incubation phase was observed in pH = 7.00 and 11.00 solutions. Additionally, there appeared to be a radial pH variation within the gap over time. The pH value is the lowest at the gap mouth, which is in line with the in situ optical observation result that the severely corroded region is at the mouth of the gap. The decrease in pH value inside results in the negative shift of open circuit potential (OCP) and the initiation of CC of 201-SS. The increased anodic dissolution rate in the acidic solution accelerates the breakdown of passive film inside, reducing the initiation time and stimulating the spread of CC.

Effect of Modified Biochar Prepared by Co-pyrolysis of MgO on Phosphate Adsorption Performance and Seed Germination.

Biochar is currently used as a phosphate adsorbent in water and subsequently as a soil amendment. In this study, modified biochar was prepared directly by co-pyrolysis of MgO and rice straw, and a preliminary ecotoxicological assessment was performed before the application of modified biochar to soil. The effects of single factors, such as pyrolysis temperature, dosage, pH, and coexisting ions, on phosphate adsorption performance were investigated. In addition, after phosphate adsorption, the effects of modified biochar leachate on the germination of corn and rice seeds were examined. The results showed that phosphate adsorption by the modified biochar first increased and then decreased as the pyrolysis temperature increased, with modified biochar prepared at 800 °C showing the greatest adsorption. In addition, a comprehensive cost analysis showed that the best phosphate adsorption effect of modified biochar was achieved at a dosage of 0.10 g and a solution pH of 3. In contrast, the presence of competitive coexisting ions, Cl- , NO3 - , CO3 2- , and SO4 2- , reduced the phosphate adsorption capacity of the modified biochar. The adsorption kinetics results revealed that the process of phosphate adsorption by the modified biochar was more in line with the pseudo-second-order model and dominated by chemisorption. Moreover, the adsorption isotherm results indicated that the process was more in line with the Langmuir model and dominated by monomolecular layer adsorption, with a maximum adsorption of 217.54 mg/g. Subsequent seed germination tests showed that phosphate-adsorbed modified biochar leachate had no significant effect on the germination rate of corn seeds, whereas it improved the germination rate of rice seeds. Together, these results provide guidance for the application of modified biochar firstly as an adsorbent of phosphate and subsequently as a soil remediator.

New insights into brominated epoxy resin type WPCBs pyrolysis mechanisms: Integrated experimental and DFT simulation studies.

Pyrolysis is a recycling technology for waste circuit boards (WPCBs) with a wide range of applications. In this research, the brominated epoxy resin (BER) type WPCBs were taken as the research object, and the optimal pyrolysis process parameters were determined. Combined with experiments and density functional theory (DFT) calculations, the pyrolysis gaseous generation pattern and product distribution of BER type WPCBs were analyzed, and the generation mechanism of phenol, bromide and other pyrolysis products was investigated in depth. The results of the study showed that the pyrolysis rate of WPCBs exceeded 95 % under optimal reaction conditions. In the initial phase of the pyrolysis of WPCBs, the BER's CO bonds and a portion of Ph-Br bonds will be broken, leading to the production of intermediates such propylene oxide, bisphenol A, isopropyl alcohol, tetrabromobisphenol A and HBr. Among them, propylene oxide can generate ethylene oxide through free radical reaction. In the second stage, intermediates such as bisphenol A undergo homolytic cleavage and radical addition to form phenols, bromides, alcohols, ketones and other pyrolysis products.

Clay mineral as catalysis for controlling the nitrogen containing pollutants during sewage sludge pyrolysis.

Pyrolysis technology is considered one of the most promising processes for the environmentally friendly disposal of sewage sludge (SS), as it can neutralize pathogens, reduce hazardous substances, and promote the immobilization of heavy metals. However, nitrogen-containing gases produced in SS pyrolysis can be converted to nitrogen oxides, causing serious environmental pollution. In this study, we investigated the evolution of the nitrogen (N) element in rapid pyrolysis of SS and explored the effect of clay minerals (attapulgite, montmorillonite, and kaolin) in regulating N conversion. The results showed that the higher temperature (800 °C) could promote the conversion of pyrroles/pyridines and NOx precursors in char to N2 (the conversion rate was 32.76 %), and clay minerals catalyzed the cleavage of N-containing macromolecules in the bio-oil, reducing the N content in bio-oil from 28.70 % to 6.23 %, and was conducted to realize the denitrification of bio-oil. Notably, the attapulgite (ATP) on N migration was more effective and could reduce the yield of NOx precursors from 23.80 % to 10.55 % by capturing NH4* and inhibiting the secondary reaction, while catalyzing the removal of N2 from pyridine/pyrrole (N2 production increased to 34.38 %). MgO and CaO in the clays played a major role in facilitating the conversion of char-N to N2, and clay structures loading on the biochar surface promoted the catalysis of N-containing volatiles to N2 by metal oxides. This study provides a viable and harmless approach to SS minimization.

Quantum chemical study on the catalytic debromination mechanism of brominated epoxy resins.

The study employed Density Functional Theory (DFT) to investigate the catalytic debromination mechanism of brominated epoxy resins (BERs) by iron (Fe) and copper (Cu) catalysts. By introducing electric field (EF), intramolecular electron transfer and polarization effects on BERs debromination were explored and experimentally validated. Results indicated that the bond dissociation energy (BDE) of the C-Br bond was 312.27 kJ/mol without catalysis, while with Fe, Cu, and EF, it was 114.47 kJ/mol, 94.85 kJ/mol, and 292.59 kJ/mol, respectively, enhancing reactivity. EF parallel to the C-Br bond and oriented toward the C atom, altered electrostatic potential and dipole moment around C-Br bond, leading to 68.60% and 50.19% increment in electronic contribution difference and molecule polarity, respectively, thereby reducing the C-Br BDE. Fe and Cu facilitated electron transfers with BERs, inducing reactions between their negative electrostatic potentials and Br's positive potential, changing electron sharing, resulting in 19.87% and 12.11% increase in polarity, respectively, and further BDE reduction. Structural modifications by the EF and catalysts also intensified van der Waals forces with bromine atoms and decreased spatial hindrance, collectively making C-Br bond breakage easier. Experiments revealed the EF enhanced BERs' debromination efficiency but hindered Fe/Cu's catalysis at lower temperatures.

A combined and sustainable approach and a novel mechanism for recovering Bi, Au and Ag from high-chloride leachate of waste printed circuit board smelting ash.

High-chloride leachate is a solution rich in precious metals that is produced in chloride hydrometallurgy. It has high levels of both rare and precious metals and hazardous chloride ions, and resource recovery from this solution and its safe disposal have become key objectives in the field of hydrometallurgy. In this study, a sustainable process involving "ultrasound-assisted precipitation-Pb powder cementation" was proposed for the stepwise separation and high-value utilization of Bi, Au and Ag obtained from high-chloride leachate. Targeted separation and conversion of Bi were achieved by precipitation-re-acid hydrolysis-ultrasonication-assisted coprecipitation-centrifugal purification. Under the optimal process conditions, the removal rate of Bi reached 99.52%, while the loss rates of Au and Ag were only 4.63% and 8.72%, respectively. Single-factor experiments of Au and Ag cementation by Pb powder showed that the recovery rates of precious metals could be improved by increasing the temperature, raising the solution pH, and applying mechanical force and ultrasonication. A possible reaction mechanism for Au and Ag cementation with Pb powder was proposed based on macroscopic kinetic analysis and microscopic mineral characterization. This work provides technical support and a theoretical basis for the separation and enrichment of rare and precious metals in chloride hydrometallurgy.

Co-pyrolysis of textile dyeing sludge/litchi shell and CaO: Immobilization of heavy metals and the analysis of the mechanism.

To relieve the secondary contamination of heavy metals (HMs), the synergistic effect of co-pyrolysis of textile dyeing sludge (DS)/litchi shell (LS) and CaO on the migration of HMs was demonstrated in this study. The proportions of Cu, Zn, Cr, Mn, and Ni in the F4 fraction increased to 75%, 55%, 100%, 50%, and 62% at the suitable CaO dosages. When 10% CaO was added, the RI value of DLC-10% was reduced to 7.89, indicating low environmental risk. The characterizations of the physicochemical properties of biochar provided support for the HMs immobilization mechanism. HMs combined with inorganic minerals or functional groups to form new stable HMs crystalline minerals and complexes to achieve immobilization of HMs. The pH value and pore structure also play an important role in improving the immobilization performance of HMs. In conclusion, the results provided a new direction for the subsequent harmless treatment of HMs-enriched waste.

Magnetized algae catalyst by endogenous N to effectively trigger peroxodisulfate activation for ultrafast degraded sulfathiazole: Radical evolution and electron transfer.

An innovative Fe-N co-coupled catalyst MN-2 was prepared from waste spirulina by co-pyrolysis as a highly active carbon-based catalyst for the activation of peroxydisulfate (PDS) for the degradation of sulfathiazole (ST). The protein-rich raw material Spirulina provided sufficient N during the pyrolysis process, thus achieving N doping without an additional nitrogen source, optimizing the interlayer structure of the biochar material and effectively inhibiting the leaching of the ligand metal Fe. MN-2 showed highly efficient catalytic activity for peroxydisulfate (PDS), with a degradation efficiency of 100% for ST within 30 min and a kinetic constant (kobs) reached 0.306 min-1, benefiting from the excellent adsorption ability of MN-2 forming MN-2-PDS* complexes and the electron transfer process generated by Fe3+ and Fe2+ cycling, oxygen-containing functional groups. The effects of PDS dosage, initial pH and coexisting anions on the oxidation process were also investigated. Free radical quenching, electron paramagnetic resonance and electrochemical measurements were employed to explain the hydroxyl (·OH) and sulfate (SO4·-) as the dominant active species and the electron transfer effect on the removal of ST. MN-2 maintained a ST removal rate of 84% after four recycling experiments, showing a high reusability performance. This work provides a simple way to prepare magnetized N-doped biochar, a novel catalyst (MN-2) for efficient activation of PDS for ST degradation, and a feasible method for removing sulfanilamide antibiotics in water environment.

Factors influencing the success of cryopreserved parathyroid autotransplantation: A systematic review.

Permanent hypoparathyroidism is a postoperative complication of thyroid and parathyroid surgery and can be cured by cryopreserved parathyroid autotransplantation (CPAT). However, due to the lack of unified and standardized guidelines, the limited ability of the parathyroid tissue itself to withstand cryopreservation, and some yet-to-be-defined processes or technologies, the success rate of cryopreserved parathyroid autotransplantation varies between institutions; it is low for some institutions and high for others. Due to the sparsity of data, views vary on which factors most influence the success rate of cryopreserved parathyroid autotransplantation. In this review, we analyzed the following probable influencing factors: ischemic period before cryopreservation; processes of cryopreservation and thawing, including freezing medium; freezing and thawing methods; duration of cryopreservation; examination of the graft before transplantation; graft site; mass of transplanted tissue fragments; blood calcium level; and the evaluation criteria for cryopreserved parathyroid autotransplantation success. Although the effects of these factors are debatable, we hypothesized that examining them in the above-given order to determine whether they affect the success rate of cryopreserved parathyroid autotransplantation could be beneficial to maximizing the success rate. Our findings led us to conclude that cryopreserved parathyroid autotransplantation operations should be standardized. Standardized guidelines for cryopreserved parathyroid autotransplantation that include such factors as ischemic period time, freezing and thawing methods, and recipient status should be established based on a comprehensive analysis of these factors.

Effect of Matrix Metalloproteinase 23 Accelerating Wound Healing Induced by Hydroxybutyl Chitosan.

Skin wounds may cause severe financial and social burden due to the difficulties in wound healing. Original inert dressings cannot meet multiple needs in the process of wound healing. Therefore, the development of materials to accelerate healing progress is essential and urgent. In the previous study, we found that the homogeneously synthesized hydroxybutyl chitosan (HBCS) had an effective performance in promoting wound healing. Proteomic analysis of the same specimen suggested that matrix metalloproteinase 23 (MMP23) may play a key role in HBCS expediting the progress of wound healing. In this work, we aim to reveal the underlying mechanism of MMP23 in the dynamic process of cutaneous proliferation and repair period. In order to regulate the expression level of MMP23 in the local wound area, we leaded in adeno-associated virus (AAV) to specifically decreased expression quantity of MMP23 in rat skin. In contrast to the negative control groups, we found that the wound closed faster and the collagen fibers and neovascularization were significantly increased in AAV groups. These findings highlighted that MMP23 was involved in wound healing after traumatic injury, and managing the expression of MMP23 could be a potential intervention target to accelerate wound healing.

Characterization and Co-Adsorption Mechanism of Magnetic Clay-Biochar Composite for De-Risking Cd(II) and Methyl Orange Contaminated Water.

The application of the adsorption method in sewage treatment has recently become a hot spot. A novel magnetic clay-biochar composite (BNT-MBC) was fabricated by co-pyrolysis of bentonite and biomass after being impregnated with Fe (NO3)3·9H2O. Its adsorption capacity for Cd(II) and methyl orange was approximately doubled, reaching a maximum of 26.22 and 63.34 mg/g, and could be easily separated from the solution by using external magnets with its saturation magnetization of 9.71 emu/g. A series of characterizations including surface morphology and pore structure, elemental analysis, functional group analysis and graphitization were carried out, showing that the specific surface area was increased 50 times by loading 20 wt.% bentonite, while its graphitization and oxygen-containing functional groups were also enhanced. The isotherm fitting indicated that Cd(II) was adsorbed in multiple layers, while methyl orange was in both monolayer and multilayer adsorptions. The kinetic fitting indicated that chemisorption was the rate-limiting step of both, and it was also a complex process controlled by two steps with the fitting of intra-particle diffusion. In the binary system of Cd(II) and methyl orange, the co-existing pollutants facilitated the adsorption of the original one, and there was no competition between adsorption sites of Cd(II) and methyl orange. BNT-MBC also exhibited good reusability and can be magnetically recovered for recycling. Thus, the magnetic clay-biochar composite BNT-MBC is a cost-effective and promising adsorbent for simultaneous removing Cd(II) and methyl orange from wastewater.

Effect of CeO2-Reinforcement on Pb Absorption by Coconut Coir-Derived Magnetic Biochar.

Magnetic separable biochar holds great promise for the treatment of Pb2+-contaminated wastewater. However, the absorption effect of unmodified magnetic biochar is poor. Considering this gap in knowledge, CeO2-doped magnetic coconut coir biochar (Ce-MCB) and magnetic coconut coir biochar (MCB) for Pb2+ absorption were prepared by the impregnation method, and the efficiency of Ce-MCB for Pb2+ absorption was evaluated in comparison with MCB. Conducting the absorption experiments, the study provided theoretical support for the exploration of the absorption mechanism. The quantitative analysis exposed that the enhanced absorption capacity of Ce-MCB was attributed to the increase in oxygen-containing functional groups and mineral precipitation. The Langmuir and Freundlich isotherm model showed that Ce-MCB is a suitable adsorbent for Pb2+. The absorption characteristics of Ce-MCB was fit well with the pseudo-second-order (PSO) and Langmuir models, which revealed that the absorption of Pb2+ in water was monolayer chemisorption with a maximum theoretical adsorption capacity of 140.83 mg·g-1. The adsorption capacity of Ce-MCB for Pb(II) was sustained above 70% after four cycles. In addition, the saturation magnetization intensity of Ce-MCB was 7.15 emu·g-1, which was sufficient to separate out from the solution. Overall, Ce-MCB has wide application prospects in terms of biomass resources recycling and environmental conservation.

Nitrogen-Doped TiO2/Nitrogen-Containing Biochar Composite Catalyst as a Photocatalytic Material for the Decontamination of Aqueous Organic Pollutants.

In this study, a waste walnut shell-derived biochar enriched with nitrogen (N-biochar) is mixed with nitrogen-doped TiO2 (N-TiO2) to fulfill an affordable composite material for the degradation of methyl orange (MO). Results showed that porous structure and oxygen-containing functional groups of biochar facilitate contact with MO during the reaction process. Meanwhile, doped nitrogen has a positive effect on improving the reaction activity due to the existence of a substituted state and a gap state in the catalyst. It was revealed that the N-TiO2/N-biochar (NCNT0.2/1) exhibited better photocatalytic degradation efficiency (97.6%) and mineralization rate (85.4%) of MO than that of TiO2, N-TiO2, and TiO2/N-biochar due to its stronger synergistic effect of N, TiO2, and biochar, in accordance with its high charge separation by photoluminescence (PL) analysis. Trapping experiments showed that ·OH is the predominant active species during the decolorization and mineralization process of MO. After five repeated use, the loss of activity of the catalyst was negligible. In addition, the catalytic degradation process was consistent with the pseudo-first-order kinetic model with the rate constant of 4.02 × 10-2 min-1.

Efficient Adsorption of a Sulfonamide Antibiotic in Aqueous Solutions with N-doped Magnetic Biochar: Performance, Mechanism, and Reusability.

Conventional biochar has limited effectiveness in the adsorption of sulfonamide antibiotics, while modified biochar exhibits greater adsorption potential. Residues of sulfamethoxazole (SMX) in the aquatic environment can threaten the safety of microbial populations as well as humans. In this study, iron-nitrogen co-doped modified biochar (Fe-N-BC) was prepared from palm fibers and doped with Fe and urea via synthesis at 500 °C. Fe-N-BC has a richer surface functional group based on elemental content, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The Brunauer-Emmett-Teller (BET) specific surface area test exhibited Fe-N-BC, which possessed a greater surface area (318.203 m2/g) and a better developed pore structure (0.149 cm3/g). The results of the hysteresis loop and the Raman spectrum show that Fe-N-BC has a higher degree of magnetization and graphitization. Fe-N-BC showed a remarkable adsorption capacity for SMX (42.9 mg/g), which could maintain 93.4% adsorption effect after four cycles, and 82.8% adsorption capacity in simulated piggery wastewater. The adsorption mechanism involves pore filling, surface complexation, electrostatic interactions, hydrogen bonding, and π-π EDA interactions. The results of this study show that Fe-N-BC prepared from palm fibers can be a stable, excellent adsorbent for SMX removal from wastewater and has promise in terms of practical applications.

Enhanced phosphate adsorption and desorption characteristics of MgO-modified biochars prepared via direct co-pyrolysis of MgO and raw materials.

Biochar modified by metal ions-particularly Mg-is typically used for the effective recovery of phosphorous. In this study, MgO-modified biochars were synthesized via the direct co-pyrolysis of MgO and raw materials such as rice straw, corn straw, Camellia oleifera shells, and branches from garden waste, which were labeled as MRS, MCS, MOT, and MGW, respectively. The resulting phosphate (PO) adsorption capacities and potential adsorption mechanisms were analyzed. The PO adsorption capacities of the biochars were significantly improved after the modification with MgO: MRS (24.71 ± 0.32 mg/g) > MGW (23.55 ± 0.46 mg/g) > MOT (15.23 ± 0.19 mg/g) > MCS (14.12 ± 0.21 mg/g). PO adsorption on the modified biochars was controlled by physical adsorption, precipitation, and surface inner-sphere complexation processes, although no electrostatic attraction was observed. Furthermore, PO adsorbed on modified biochars could be released under acidic, alkaline, and neutral conditions. The desorption efficiency of MRS was modest, indicating its suitability as a slow-release fertilizer.

Numerical Simulation of an Improved Updraft Biomass Gasifier Based on Aspen Plus.

In this paper, numerical investigation and optimization is conducted upon an improved updraft gasifier which is expected to overcome the weakness of conventional updraft gasifier. The comprehensive Aspen Plus model of the improved updraft gasifier is based on the RYield and RCSTR reactor. The tar prediction model is constructed, and the yield of tar is determined by the volatile of biomass and gasification temperature. The Aspen Plus simulation results agree very well with experiment results for the product yields and gasification efficiency, which shows the accuracy of the Aspen Plus model. The tar content in syngas of the improved gasifier is proved to be much lower than that of the conventional one by this model. The inflection point of the gasification efficiency occurs when air ratio is 0.25, and the optimum steam proportion in the air is 7.5%. Such a comprehensive investigation could provide necessary information for the optimal design and operation of the improved updraft gasifier.

Study on Efficient Adsorption Mechanism of Pb2+ by Magnetic Coconut Biochar.

Lead ion (Pb2+) in wastewater cannot be biodegraded and destroyed. It can easily be enriched in living organisms, which causes serious harm to the environment and human health. Among the existing treatment technologies, adsorption is a green and efficient way to treat heavy metal contamination. Novel KMnO4-treated magnetic biochar (KFBC) was successfully synthesized by the addition of Fe(NO3)3 and KMnO4 treatment during carbonization following Pb2+ adsorption. SEM-EDS, XPS, and ICP-OES were used to evaluate the KFBC and magnetic biochar (FBC) on the surface morphology, surface chemistry characteristics, surface functional groups, and Pb2+ adsorption behavior. The effects of pH on the Pb2+ solution, initial concentration of Pb2+, adsorption time, and influencing ions on the adsorption amount of Pb2+ were examined, and the adsorption mechanisms of FBC and KFBC on Pb2+ were investigated. The results showed that pH had a strong influence on the adsorption of KFBC and the optimum adsorption pH was 5. The saturation adsorption capacity fitted by the model was 170.668 mg/g. The successful loading of manganese oxides and the enhanced oxygen functional groups, as evidenced by XPS and FTIR data, improved KFBC for heavy metal adsorption. Mineral precipitation, functional group complexation, and π-electron interactions were the primary adsorption processes.

Synchronous bio-degradation and bio-electricity generation in a Microbial Fuel Cell with aged and fresh leachate from the identical subtropical area.

Seasonal leachate from both sealed and operating landfill in the identical district were employed as the sole substrate in the Microbial Fuel Cell (MFC) to evaluate the power output performance and aqueous organic waste disposal. The electrical performance was characterized to study the power generation, while the Chemical Oxygen Demand (COD) removal ratio and Coulombic Efficiency (CE) were calculated to illustrate the substrate disposal effect. In addition, Scanning Electron Microscope (SEM) on the operated anode was conducted to preliminarily explain the microbial community difference, and the phylogenetic tree constructed on the cultivated microorganism was an insight into the dominant bacteria suitable for leachate degradation. It was found that the MFCs inoculated with seasonal leachate from both sealed and operating landfill could generate electricity successfully. Although the fresh leachate-inoculated MFCs had better electrical output performance (22.7-25.6 W/m3 versus 6.61-7.48 W/m3) and COD removal efficiency (55.8%∼61.7% versus 47.7%∼51.4%), the CEs were only 4.3%∼7.6%, which were lower than the aged leachate inoculated group (5.9%∼11.3%). Based on the SEM images and the phylogenetic tree of the operated anode, the composition impacts on the microbial community and power output performance were verified, which was instructive for the leachate disposal in the MFC.

Magnetically Recyclable Loofah Biochar by KMnO4 Modification for Adsorption of Cu(II) from Aqueous Solutions.

Novel KMnO4-modified loofah biochar loaded with nano-Fe2O3 (FMLB) was successfully synthesized for Cu(II) adsorption. Nitrogen adsorption method, scanning electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, and other characterization measurements were used to evaluate the physical and chemical properties of FMLB and nano-Fe2O3-loaded biochar (FLB). The results show that the adsorption behavior of Cu(II) can be best fitted by the Langmuir isotherm model and the pseudo-second-order (PSO) kinetic model, indicating that the surface of FMLB was composed of homogeneous adsorption, and chemical adsorption dominated the adsorption process under optimal reaction conditions. The adsorption capacity of FMLB is improved by 42.86% compared to FLB, and it remained over 75% after four cycles. The inner-sphere complexes with manganese oxide (MnO x ) and oxygen-containing functional groups, as well as electrostatic interaction, physical adsorption, and ion exchange, play important roles in Cu(II) adsorption. The saturation magnetization of FMLB was 10.41 emu/g, ensuring that it can be easily separated from aqueous solutions. Therefore, magnetically recyclable biochar modified by KMnO4 is a feasible method for Cu(II) adsorption.