Superior Removal Performance Research Articles

Rapid and efficient removal of organophosphorus pollutant and recovery of valuable elements: A boosted strategy for eliminating organophosphorus from wastewater

Considering the significant hazards of organophosphorus compounds (OPs) and the potential crisis of phosphorus (P) resource shortage, there is a great necessity to develop economically feasible, highly effective, and sustainable strategies to remove OPs and recover P resources. In this study, low-cost microscale zero-valent iron (mZVI) was used to activate hydrogen peroxide for the rapid and efficient elimination of Tetrakis(hydroxymethyl)phosphonium sulfate (THPS) from the aquatic environment. Compared to the conventional Fenton reaction and commercial mZVI, mZVI/H2O2-based Fenton-like reaction exhibited superior removal performance for THPS. The removal mechanism of the mZVI/H2O2 system for THPS was thoroughly elucidated through the identification of reactive oxygen species, characterization analysis, and theoretical calculation. Furthermore, the valuable components of the degradation products were successfully recovered through thermally induced precipitation of the sample followed by high-temperature calcination. The mZVI/H2O2 system has demonstrated significant advantages in removing organic compounds from various types of actual wastewater and improving the biodegradability of the wastewater. This study presented an environmentally friendly and highly efficient strategy to eliminate OPs pollution and recover P resources. It also provided an easy-to-operate method for remediating actual industrial wastewater.

Fabrication and photocatalysis of novel Z-scheme Cu2O/Cu-Ag/AgCl heterojunction possessed broad-spectrum antibacterial performance and degradation capabilities

The construction of nanostructured Z-heterostructures is a potent strategy for achieving efficient photocatalyst synthesis. Herein, a novel Cu2O/Cu-Ag/AgCl (CCAA) Z-scheme heterostructure was created via photoreduction precipitation and utilized for pollutant decomposition and microorganism inactivation. Subject to visible light (λ > 420 nm) illumination, specimen CCAA-2 demonstrated superior photodegradation competence for Congo Red (CR), achieving a degradation rate of 92.6 % within 60 min. The superior removal performance is attributed to the Z-scheme heterostructure, featuring precise interfacial contact, and the combined effect of adsorption and photocatalytic activity. Meanwhile, the optimal sample, CCAA-2, was able to achieve 100 % inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) within 15 min under visible light. The photocatalytic performance of CCAA nanocomposites is primarily attributed to the surface plasmon resonance (SPR) effect of the noble metal Ag and the fabrication of Z-Scheme heterostructures to improve the utilization efficiency of electrons (e-) and holes (h+). Particularly, the photocatalytic mechanism was scrutinized via active substance capture experiments and electron spin resonance (ESR) analysis, uncovering that •O2ˉ and h+ served as key active constituents. Hence, this research presents a feasible approach for designing and constructing Z-Scheme heterojunctions for efficacious removal of contaminants from water.

COF-derived porous nitrogen-doped carbon for removal of emerging organic contaminants and efficient uranium extraction from seawater

The development of adsorbents for efficient and highly selective seawater extraction of uranium was instrumental in fostering sustainable progress in energy and addressing the prevailing energy crisis. However, the complex background composition of the marine environment, including radionuclides, organic pollutants, and a large number of co-existing heavy metal ions, were non-negligible obstacles to the extraction of uranium from seawater. The present investigation successfully employed a self-templated approach to synthesize porous nitrogen-doped carbon (PNC) derived from COF, which exhibited tremendous potential as an adsorbent for pollutant removal in environmental treatment. LZU1@PNC not only retained the structural features of the original COF-LZU1, but also overcame the acid-base instability problem commonly found in COFs. Subsequently, the removal process of two typical water pollutants on the material was investigated using 2,4-DCP and [UO2(CO3)3]4-. The results demonstrated that LZU1@PNC exhibited superior removal performance for the target pollutants compared to COF-LZU1, owing to its larger specific surface area and abundant defect structure. After six desorption-regeneration cycles, LZU1@PNC still maintained a high removal rate of the target contaminants, demonstrating the stability of this material and its excellent recyclability. In addition, based on various characterization techniques, the removal mechanism of 2,4-DCP was presumed to be mainly electrostatic attraction, hydrogen bonding, and π-π stacking interactions. Conversely, the elimination process of [UO2(CO3)3]4- predominantly relied on surface complexation phenomena. The present investigation provided new perspectives and stimulated a broader study of other COF-derived carbon materials and their modifications as adsorbents for uranium extraction from seawater and other applications.

Enhanced removal of antibiotic-resistant genes by sodium persulfate catalyzed by nanoscale zero-valent iron modified by Ginkgo biloba L. leaf

ABSTRACT In this study, nanoscale zero-valent iron (nZVI) modified by Ginkgo biloba L. leaf (G-nZVI), as an effective catalyst, exhibited excellent activation of sodium persulfate (PS), which could achieve higher removal efficiency of antibiotic-resistant genes (ARGs) in the Fen River than PS + nZVI system. This study utilizes forestry waste to address the limitations of using Fe2+/nZVI as an activator for the removal of ARGs. This approach adheres to the principle of employing waste to treat waste. The technology converts G. biloba L. leaf into plant extracts that are rich in a variety of bioactive components, rather than purifying natural biomolecules, which decreases operational complexity. In addition, the G-nZVI + PS system demonstrates superior removal performance to single components in the system. Consequently, the mechanism underlying the G-nZVI + PS treatment is attributed to peroxidation induced by radicals. In this context, the results of ARG removal by G-nZVI + PS with different G. biloba L. leaf /FeSO4·7H2O volume ratios indicated that the G. biloba L. leaf enhanced the conversion of Fe3+ to Fe2+, thereby generating more radicals through electron transfer between the biomass and G-nZVI. This research underscores the advantages of modifying G. biloba L. leaf for improved catalytic efficiency and the role of the components within the system.

Sequential bio-treatment of ammonia-rich wastewater from Chinese medicine residue utilization: Regulation of dissolved oxygen

To effectively treat actual ammonia-rich Chinese medicine residue (CMR) resource utilization wastewater, we optimized an anaerobic-microaerobic two-stage expanded granular sludge bed (EGSB) and moving bed sequencing batch reactor (MBSBR) combined process. By controlling dissolved oxygen (DO) levels, impressive removal efficiencies were achieved. Microaeration, contrasting with anaerobic conditions, bolstered dehydrogenase activity, enhanced electron transfer, and enriched the functional microorganism community. The increased relative abundance of Synergistetes and Proteobacteria facilitated hydrolytic acidification and fostered nitrogen and phosphorus removal. Furthermore, we examined the impact of DO concentration in MBSBR on pollutant removal and microbial metabolic activity, pinpointing 2.5 mg/L as the optimal DO concentration for superior removal performance and energy conservation.

Synergistic adsorption-photocatalytic degradation of tetracycline by S-scheme InVO4/ZnIn2S4 heterojunction: mechanism, toxicity assessment, and potential applications

The development of materials with dual adsorption/photocatalytic functions for the removal of difficult-to-degrade organics is a very promising and challenging strategy. In this paper, a novel S-scheme heterojunction photocatalyst, InVO4/ZnIn2S4, was successfully synthesized with a unique hierarchical structure, which provides plenty of accessible adsorption/photocatalytic sites with a high light-harvesting rate (by multiple reflections). The experimental results show that optimized InVO4/ZnIn2S4 (5-IV/ZIS) has superior removal performance, whose adsorption-photocatalytic synergistic removal of tetracycline (TET) can reach 69.31 % after 15 min and 90.69 % after 45 min. Based on the analysis of the mechanism, the excellent removal performance can be attributed to the adsorption of the target onto the material by hydrogen bonding, followed by the degradation of the adsorbed target by active substances (h+ > O2•− > e- >1O2 >•OH) generated by the S-scheme heterojunction. In addition, the possible pathways for the photocatalytic removal of TET on 5-IV/ZIS were investigated by HPLC-MS analysis. T.E.S.T. and E. coli inhibition experiments demonstrated a significant reduction in the toxicity of TET after the photocatalytic reaction. In conclusion, the novel multifunctional photocatalyst 5-IV/ZIS prepared in this study can be used for the efficient treatment of organic compounds in wastewater with a bright application prospect.

Flower shaped Zn2In2S5/FeIn2S4 as a promising S-Scheme heterojunction photocatalyst for superior ciprofloxacin removal

In recent years, refractory pharmaceutical pollutants have emerged as a major environmental and public health concern. An interesting strategy that has recently emerged is photocatalysis, which involves directly breaking down these environmental pollutants using visible light. However, the rapid combining of the photogenerated charges is a major issue with this method, leading to instability and low efficiency. This work presents the development of a Zn2In2S5/FeIn2S4 (ZIS-/FIS) heterojunction photocatalyst, which is an effective photocatalyst for the degradation of ciprofloxacin (CIP) when exposed to visible light. When compared to pure ZIS and FIS, the resultant ZIS-/FIS S-type heterojunction shows significantly better visible light-driven photocatalytic performance. Specifically, 20ZIS/FIS catalyst exhibits the highest photocatalytic efficiency for CIP breakdown, reaching 90.03% at 10 mg/L concentration in 120 min. Through scavenging experiments and ESR findings, it has been demonstrated that •O2- and •OH are the primary active species that are involved in the degrading process. The higher adsorption ability, heightened light harvesting, and increased separation rate of carriers that resulted from the synergistic effect of the components are the primary factors that are responsible for the superior removal performance. The results of this work offer a realistic reference for the construction of novel heterojunction photocatalysts for the purpose of maintaining environmental cleanliness.

Enhancing Pb2+ removal efficiency in flow-through systems using flue gas desulfurization gypsum-based porous materials: Experimental and numerical studies

This study addresses the poor permeability of flue gas desulfurization (FGD) gypsum in water remediation and further explores its potential for resource utilization. FGD gypsum-based porous materials (FGPMs) were prepared using different foaming behavior as permeable reactive barrier (PRB) media materials. The dynamic removal performance of Pb2+ was investigated, and a numerical model was developed to validate the results. The findings reveal that the adsorption mechanisms of FGPMs primarily involve ion exchange and surface precipitation. Pb2+ does not alter the structure or functional groups of the materials. By optimizing the foaming behavior to enhance pore connectivity, the adsorption capacity increased from 8.78 mg/g to 13.42 mg/g, thereby extending the service life of the PRB. The presence of closed and capillary pores hinders the dynamic removal performance of Pb2+. Furthermore, the FGPMs exhibit superior removal performance at low flow rates, low concentrations, and high column heights, as confirmed by the numerical model. These results offer valuable insights for designing and optimizing FGD gypsum-based adsorption processes to remove Pb2+ from wastewater efficiently.

Nanocomposite HKUST-1@polysulfone membrane for the adsorptive removal of tetracyclines in waters

To mitigate the presence of tetracyclines in water, it is essential to implement proper wastewater treatment processes that can effectively remove these compounds. In this work we develop a polymeric filtration membrane functionalized with nanocrystals of a metallic organic framework, designated by HKUST-1. The membrane was evaluated for the remotion of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) in water samples. The membrane was fabricated using polysulfone (PSU), polyethyleneglycol (PEG), MOF (HKUST-1), and N-methyl-2-pyrrolidone (NMP) through the nonsolvent induced phase separation (NIPS) method. The membrane that presents the best antibiotic rejection characteristics was prepared with 15 % (w/w) PSU, 3 % (w/w) PEG, 1 % (w/w) HKUST-1, and 81 % (w/w) N-methyl-2-pyrrolidone (NMP). This membrane exhibited a pure water flux of up to 76.2 L.m−2.h−1, approximately 40 times more than the one achieved for pristine membranes. Once determined the best membrane composition, a physical–chemical characterization of membrane was done. A high antibiotic rejection rate was obtained for OTC, TC, and CTC, around 91 %, 91 %, and 99 % respectively. The pH of solutions has a strong influence on membrane rejection. The results suggest that intermolecular forces such as π-π type interactions and hydrogen bonds exist between the neutral molecules of tetracyclines (pH > pKa1 and < pKa2) and HKUST-1@PSU MMM, which are greater than the electrostatic forces at pH < pKa1 or pH > pKa2. Furthermore, FTIR spectra demonstrate the formation of a Cu-tetracycline complex as another adsorption mechanism. Finally, the interaction of the tetracyclines in the mixture on the removal performance was evaluated. The study revealed that chlortetracycline (CTC) exhibited superior removal performance, even over extended periods of time, despite having a lower initial concentration in the mixture. This innovative membrane represents a new generation of highly efficient filter systems specifically designed for water purification purposes.

Enhanced removal of estrogens from simulated wastewater by biochar supported nanoscale zero-valent iron: performance and mechanism

The intensification of estrogen non-point source pollution has drawn global attention due to their contribution to ecological environment problems worldwide, and it is critical to develop effective, economic and eco-friendly methods for reducing estrogens pollution. To address the agglomeration and oxidation of nano zero-valent iron (nZVI), biochar-nanoscale zero-valent iron composite (nZVI-biochar) could be a feasible choice for estrogens removal. This study summarized biochar and nZVI-biochar preparation, characterization, and unusual applications for estrone (E1), 17β-estradiol (E2), and estriol (E3) removal. The properties of biochar and nZVI-biochar in characterization, effects of influencing factors on the removal efficiency, adsorption kinetics, isotherm and thermodynamics were investigated. The experiment results showed that nZVI-biochar exhibited the superior removal performance for estrogens pollutants compared to biochar. Based on the quasi-second-order model, estrogens adsorption kinetics were observed, which supported the mechanism that chemical and physical adsorption existed simultaneously on estrogens removal. The adsorption isotherm of estrogens could be well presented by the Freundlich model and thermodynamics studies explained that nZVI-biochar could spontaneously remove estrogens pollutants and the main mechanisms involved π-π interaction, hydrophobic interaction, hydrogen bonding and degradation through ring rupture. The products analyzed by GC–MS showed that estrogens degradation was primarily attributed to the benzene ring broken, and Fe3+ promoted the production of free radicals, which further proved that nZVI-biochar had the excellent adsorption performances. Generally, nZVI-biochar could be employed as a potential material for removing estrogens from wastewater.Graphical

Superior removal performance for methylene blue onto Spartina alterniflora biochar via solvothermal method: Equilibrium, kinetics and mechanism analyses

In this study, an activated biochar derived from Spartina alterniflora (SRHH) was innovatively synthesized to efficiently remove dye contaminants from aqueous solution. A series of characterizations exhibited that solvothermal process effectively increased the mesopores and functional group structure (OH, NHR, CO, CO and RNCO) of the nanomaterial, which could also acquire amorphous carbon-doped biochar with less energy consumption. Moreover, the results showed that the as-prepared sample in a solvothermal kettle at 180 °C displayed superior dye adsorption and degradation performance, and the removal efficiency entirely could reach up to 93% within 4 h at neutral condition. The adsorption process was both consistent well with the pseudo-second-order and intraparticle diffusion models, indicating that diffusion resistance within the particle pore size and chemical action might be predominantly controlled factor. Therefore, the prepared catalyst has enormous potential in the removal of organic pollution as a low-cost and economical in-situ remediation material.

Poly(ionic liquid) blended polyphenylene sulfone ultrafiltration membranes with enhanced surface hydrophilicity and antifouling performance

Membrane fouling is a key challenge in the process of utilizing polyphenylene sulfone(PPSU) ultrafiltration (UF) membranes. To address this issue, an amino-functionalized poly(ionic liquid), poly(1-vinyl-3-propylamine imidazolium bis(trifluoromethane sulfonyl) imide) (PIL[TFSI]), was synthesized via free radical polymerization and incorporated into the prepared UF membranes-based PPSU with nanochannels through nonsolvent induced phase separation method. 1H NMR, ATR-FTIR, XPS and EDS spectra verified the introduction of PIL[TFSI]. The AFM and SEM images showed the membrane possessed a classical asymmetrical structure, featuring a higher surface roughness and dense cortex with pits. The decreased water contact angle by the incorporation of PIL[TFSI] indicates the formation of an improved hydrophilic membrane surface. The hydrophilicity of the blended membranes was enhanced by the increasing incorporation of PIL[TFSI]. Meanwhile, the flux decreased slightly, but the selectivity improved significantly. The PIL[TFSI]/PPSU UF membrane with 5% PIL[TFSI] maintained a flux (275 L/m2 h) and a high rejection for bovine serum albumin (BSA) (>99.9%). Additionally, the blended membrane has a superior removal performance for Congo red (>99.9%) and Evans blue (>99.9%). More importantly, the PIL[TFSI]/PPSU UF membranes present excellent antifouling with an increased flux recovery rate from 60.2% to 91.1%. Furthermore, the existence of hydrogen bonds and π-π interactions between PIL[TFSI] and PPSU is conducive to the good stability and sustained hydrophilicity of blended membrane even after continuous immersion for a month.

Analysis of natural photocatalysts derived from spartina alterniflora with superior removal performance of pollutant

Spartina alterniflora, as an invasive alien species, has been studied in terms of its potential use in immobilization and synergistic photocatalysis against dye contaminants for the first time. Microscopic characterization and Fourier transform infrared (FTIR) spectroscopy results confirmed the presence of abundant 3D wormhole-like pore structures and active functional groups (-OH, –NH2, CO, Si–O–Si). Moreover, the existence of SiO2 was connected the metal oxides with polar groups, which could proceed entire reaction procedure subsequently. Transition metal oxides (such as Fe2O3, TiO2, MnO2 and NiO) contained in photocatalysts might effectively promote the organics decomposition by the visible light excitation. The highest dye removal efficiency of 92.03% could be reached with the addition of 0.02 g photocatalyst. The capture experiment confirmed that the h+ was the dominant active substance during the photocatalytic degradation process. Density functional theory (DFT) calculations verified that the functional groups (-COOH, –OH and –NH2) were exceptional adsorption sites for catalyst, and the calculated adsorption energy were all negative with the order of SRHH-NH2 (−2.712688 eV) < SRHH-OH (−2.075601 eV) < SRHH-COOH (−1.283141 eV), which confirmed that interface interaction effectively bound cationic dyes through the formation of hydrogen bonds at the catalysts-water interface, further accelerating the reaction rate of the entire photocatalytic reduction of dye molecules. Therefore, this work provides a feasible synthesis of natural photocatalysts using solid waste, which suggests excellent adsorption and photocatalysis properties for the treatment of organic industrial pollutant.

Constructing coconut shell biochar/MXenes composites through self-assembly strategy to enhance U(VI) and Cs(I) immobilization capability

Herein, a biochar-based composite (Ti3C2Tx@biochar-PDA/PEI) was constructed by decorating Ti3C2Tx and polydopamine on coconut shell biochar via electrostatic self-assembly method. Different characterization techniques were applied to explore the structure, morphology and composition of the sorbents. It was found that the higher porosity and diverse functional groups were conducive for Ti3C2Tx@biochar-PDA/PEI to capture radionuclides, and the water environmental conditions made a great contribution to the adsorption process. The process of removing U(VI)/Cs(I) well complied with the Langmuir isotherm and Pseudo-second-order equations, which indicated that the single layer chemical adsorption occurred on the solid liquid interface. Meanwhile, this produced composite exhibited superior removal performance under complex co-existing ion environment, and the maximum adsorption amounts of U(VI) and Cs(I) reached up to 239.7 and 40.3 mg g−1. Impressively, this adsorbent still exhibited good adsorption performance after three cycles of regeneration. The spectral analysis and DFT calculation demonstrated that adsorption of U(VI) might be a chemical process, while the adsorption of Cs(I) should be ion exchange or electrostatic attraction. This study demonstrated the potential application of Ti3C2Tx@biochar-PDA/PEI as an effective remediation strategy for radioactive wastewater cleanup.Graphical

Selective dechlorination degradation of chlorobenzenes by dual single-atomic Fe/Ni catalyst with M-N/M-O active sites synergistic

Removal and detoxification of chlorobenzenes have attracted public concern, multiple active sites single-atom Fe and single-atom Ni composite nitrogen-doped graphene (FeSA/CN/NiSA) cathode catalyst supplied generation and adsorption capacity of hydrogen and hydroxyl active species. M-O active sites coupled with M-N improved activity and stability of the catalyst, and decreased bond breaking energy barrier of C-Cl, FeSA/CN/NiSA-NiF cathode showed superior removal performance of chlorinated aromatic hydrocarbons (monochlorobenzene: 98.9%, dichlorobenzene: over 90.4%, trichlorobenzene: over 85.7%) and selectivity. Chlorobenzenes were dechlorinated under low stepwise voltage on the FeSA/CN/NiSA-NiF cathode. The efficiencies of stepwise dechlorination reactions of chlorobenzenes were all above 76%, Faradaic efficiencies were above 71.8%. The FeSA/CN/NiSA-NiF cathode was not sensitive to the molecular structure and has overcome the high energy barrier of chlorobenzenes molecular structure. The electrophilic attack of H*ads formed hyperconjugation bond weakened the possibility of the Cl atom forming a bond with the benzene ring, and was favorable for the Cl position to achieve single-electron transfer dechlorination. The selective stepwise dechlorination degradation of chlorobenzenes by FeSA/CN/NiSA-NiF cathode with multiple active sites demonstrated the advantaged performance of M-O and M-N active sites coupled synergistic in electrochemical reduction and degradation, providing a strategy for product-selective degradation of chlorinated aromatic hydrocarbons.

Surfactant-Modified Hydrophobic Biochar Derived from Laver (Porphyra haitanensis) with Superior Removal Performance for Kitchen Oil

Surfactant-Modified Hydrophobic Biochar Derived from Laver (Porphyra haitanensis) with Superior Removal Performance for Kitchen Oil

Computer chip-inspired design of nanocellulose/carbon dots hydrogel as superior intensifier of nano-sized photocatalyst for effective Cr(VI) removal

Hydrogel, a common carrier of photocatalyst that suffers from compromised catalytic efficiency, is still far from practical application. Herein, based on “computer chip-inspired design”, a novel nanocellulose/carbon dots hydrogel (NCH) was fabricated as superior intensifier instead of common carrier of sodium titanate nanofibre (STN), where carbon dots (CDs) enhanced amino group-induced adsorption for Cr(VI), promoted photocatalytic properties of STN via transferring the photogenerated electron-hole pairs and improved amino group-induced desorption for reduced product (Cr(III)) via electrostatic repulsion, showing an efficiency of 1 + 1 > 2. Adsorption and photocatalysis experiments demonstrated superior removal performance of the NCH incorporating STN, as shown by theoretical maximum adsorption capacity of 425.74 mg/g and kinetic constant of 0.0374 min−1 in the photocatalytic process, which was nearly 6.6 and 7.3 times of STN. A series of experiments was conducted to confirm the novel mechanism of CDs-enhanced adsorption–photocatalysis–desorption synergy. This work not only provides new insights into the fabrication of a superior intensifier for nanosized photocatalyst, but also proposes one new mechanism of CDs-enhanced adsorption–photocatalysis–desorption synergy, which is helpful for designing and optimizing nanosized photocatalyst.

A 3D porous structured cellulose nanofibrils-based hydrogel with carbon dots-enhanced synergetic effects of adsorption and photocatalysis for effective Cr(VI) removal

Increasing chromium pollution poses a significant threat to the global environment and human health, and it is critical to remove hexavalent chromium (Cr(VI)) from water. Hence, a three-dimensional (3D) porous structured cellulose nanofibrils-based hydrogel (CNH) was synthesised using cellulose nanofibrils (CNs), carbon dots (CDs) and α-FeOOH, with CDs-enhanced synergetic effects of adsorption and photocatalysis for removing Cr(VI). In the CNH, CNs were conducted as a natural frame to construct a 3D porous structure increasing the specific surface area and providing additional active sites, CDs enhanced the amino group-induced adsorption for Cr(VI) and facilitated the transfer of photogenerated electron from α-FeOOH, and α-FeOOH was nanosized photocatalyst for generating photogenerated electron. A series of adsorption and photocatalysis experiments showed the superior adsorption-photocatalytic performance, as demonstrated by the large adsorption capacity and high kinetic constant of 115.98 mg/g and 0.06380, respectively, which was about 8 and 26 times as high as that of α-FeOOH. This superior removal performance was due to the mechanism of CDs-enhanced adsorption-photocatalysis synergy. This study not only provided a novel strategy for preparing green and efficient bifunctional materials for high-efficient Cr(VI) removal but also proposed a corresponding novel mechanism for CDs-enhanced synergetic effect of adsorption and photocatalysis.

Ammonia removal using thermally induced phase separation PVDF hollow fibre membrane contactors

Hollow fibre membrane contactors (HFMCs) are a promising new technology for ammonia recovery but are limited by the mass transfer efficiency as well as their chemical resistance and physical strength. Thermally Induced Phase Separation (TIPS) Polyvinylidene Fluoride (PVDF) membranes offer a new HFMC option for ammonia recovery due to their superior removal performance and physicochemical properties. In this study, two chemically robust TIPS PVDF HFMCs were synthesized and evaluated for the recovery of ammonia from wastewater. The HFMCs displayed an uncompromised high tensile strength of up to 19.12 ± 0.93 MPa under a long-term chemical exposure against acids, alkalis, and oxidants over 60 days of immersion. The HFMCs had a high air permeance flux of up to 1.67 ± 0.26 mol/m2/s. The crystalline structure of the TIPS PVDF membranes affected the hydrophobicity of the membranes more than pore size. Optimisation of ammonia removal was achieved by the Taguchi method for design of experiments using five operational parameters namely pH, temperature, ammonia solution velocity, concentration, and air sparging rate. Empirical evidence showed that the TIPS PVDF HFMCs achieved the highest ammonia removal of greater than 99% and a mass transfer coefficient (Kov) of up to 4.53 × 10-5 m/s. Comparatively, the Kov and flux of both TIPS PVDF membranes in this study are up to one order higher than those previously reported and could even be higher with further improvements to operating conditions. Air sparging is for the first time used in HFMCs to improve ammonia removal and is known to simultaneously reduce membrane fouling.

Preparation of diethylenetriamine-functionalized thiosulfate intercalated ZnNiAl-LDHs and its removal behavior and mechanism of U(VI)

A new composite material, diethylenetriamine-functionalized thiosulfate intercalated zinc-nickel-aluminum hydrotalcite (DETA-ZnNiAl-S2O32−-LDHs), was synthesized by introducing S2O32− between ZnNiAl-LDHs layers and grafting diethylenetriamine for functionalization modification. The morphological structure and physicochemical properties of samples were analyzed using XRD, FTIR, SEM and BET characterization. By analyzing the results of the batch removal experiments, it was found that the removal process of U(VI) by DETA-ZnNiAl-S2O32−-LDHs was more consistent with the pseudo-second-order and Langmuir isotherm models, and the process was endothermic and spontaneous. The maximum removal capacity of DETA-ZnNiAl-S2O32−-LDHs reached 558.66 mg/g at pH of 6, contact time of 6 h, sample dosage of 0.004 g and temperature of 313 K. The removal of U(VI) by DETA-ZnNiAl-S2O32−-LDHs involved adsorption and reduction: U(VI) bound to the laminar hydroxyl group and diethylenetriamine of the material through surface complexation, while the thiosulfate in the material reduced U(VI) to U(IV) and then removed it. In addition, DETA-ZnNiAl-S2O32−-LDHs still showed superior removal performance under high salinity and complex co-existing ion environment. The results suggest that DETA-ZnNiAl-S2O32−-LDHs have potential applications in the efficient remediation of radioactive wastewater.