Complex Water Matrices Research Articles

New Insights into Calcite Dissolution Mechanisms under Water, Proton, or Carbonic Acid-Dominated Conditions.

Carbonate minerals are ubiquitous in nature, and their dissolution impacts many environmentally relevant processes including preferential flow during geological carbon sequestration, pH buffering with climate-change induced ocean acidification, and organic carbon bioavailability in melting permafrost. In this study, we advance the atomic level understanding of calcite dissolution mechanisms to improve our ability to predict this complex process. We performed high pressure and temperature (1300 psi and 50 °C) batch experiments to measure transient dissolution of freshly cleaved calcite under H2O, H+, and H2CO3-dominated conditions, without and with an inhibitory anionic surfactant present. Before and after dissolution experiments, we measured dissolution etch-pit geometries using laser profilometry, and we used density functional theory to investigate relative adsorption energies of competing species that affect dissolution. Our results support the hypothesis that calcite dissolution is controlled by the ability of H2O to preferentially adsorb to surface Ca atoms over competing species, even when dissolution is dominated by H+ or H2CO3. More importantly, we identify for the first time that adsorbed H+ enhances the role of water by weakening surface Ca-O bonds. We also identify that H2CO3 undergoes dissociative adsorption resulting in adsorbed HCO3- and H+. Adsorbed HCO3- that competes with H2O for Ca acute edge sites inhibits dissolution, while adsorbed H+ at the neighboring surface of CO3 enhances dissolution. The net effect of the dissociative adsorption of H2CO3 is enhanced dissolution. These results will impact future efforts to more accurately model the impact of solutes in complex water matrices on carbonate mineral dissolution.

Insights on the degradation mechanism of neotame using UV/periodate: Roles of reactive species, kinetics, and pathways

As a new artificial sweetener (ASs), the jeopardize of neotame (NEO) to aquatic environment is attracting concern due to its widespread usage and difficulty in removing from wastewater. UV/periodate (UV/PI) is being considered as an effective process for the degradation of micropollutants in wastewater. However, there are few studies of the roles of reactive species (RS) and the effects of complex water matrices on the degradation of NEO via UV/PI. The degradation of NEO in aqueous media by UV/PI was investigated herein. NEO was effectively removed (>97 %) by UV/PI within 4 min. The degradation of NEO was mainly attributed to •OH (75.7 %), IO3• (23.0 %) and 1O2 (1.3 %) with the observed second-order rate constants of 7.71 × 109, 1.56 × 108 and 2.94 × 105 M−1 s−1, respectively. The contribution of IO3• and 1O2 to NEO degradation was greater at acidic and high PI concentrations, but significantly decreased in the presence of natural organic matter. The presence of anions in the water did not obviously impact NEO degradation. During the degradation of NEO, •OH attacked NEO through hydroxylation reaction, while IO3• and 1O2 predominantly participated in decarboxylation and amide hydrolysis reactions. Toxicity evaluation showed that the UV/PI treatment of NEO enhanced the toxicity to Vibrio fischeri within 5 min, and the toxicity reduced with the prolongation of treatment time. The study provides meaningful information on the roles of IO3• and 1O2 for NEO degradation by UV/PI.

Hemp-ball-like structured Fe3O4-hollow carbon sphere nanozymes functionalized carbon fiber cathode for efficient flow-through electro-Fenton

Electro-Fenton (EF) technology has been recognized as a highly promising electrochemical advanced oxidation process. Promoting effective contact between active species and contaminant is crucial in electrocatalysis. Herein, we had innovatively designed a unique nanozymes in the form of hemp-ball-like structures, consist of the uniform growth of Fe3O4 nanoparticles on nitrogen-doped nano hollow carbon spheres (NHCS). This catalyst was employed in a flow-through EF system with carbon felt (CF) filters serving as the work electrode. The active sites were fully exposed through the ultradispersed Fe3O4 nanoparticles, and the NHCS facilitated efficient cycling of Fe3+/Fe2+. The results showed that the generation capacity of hydroxyl radicals (·OH) was enhanced, and the oxidation flux reached 370.080 mg h−1m−2 with low energy consumption. The superiority of the hollow carrier was proved by the degradation results and COMSOL calculation for various carbon carriers. Moreover, the active catalyst exhibited adaptability in complex water matrices. This study offers a new perspective to synergize nanomaterials, EF reactions and flow-type systems.

High-density Co-Nx sites anchored on biomass-based carbon nanotubes for efficient removal of plant viruses in water

In this study, we selected rice straw, wheat straw and corn cob as raw materials to successfully prepare cobalt-nitrogen co-doped biomass-based carbon nanotubes composites (BM@CoNCNTs) with Co-Nx sites highly dispersed on porous biochar carrier, which could effectively activate peroxymonosulfate (PMS) to remove tobacco mosaic virus (TMV) in water. Particularly, BM@CoNCNTs-CC, with its confined carbon nanotubes and high-density Co-Nx sites, enhanced the Co2+/Co3+ cycle and direct adsorption of PMS to generate Co(IV)=O and 1O2, playing a dominant role. This led to the effective disruption of TMV coat protein and degradation of its genome within 5 min, achieving up to 6 log10 removal efficiency. Additionally, BM@CoNCNTs-CC/PMS system maintained efficient catalytic removal performance even in complex water matrices (river water and tap water). Overall, our research not only elucidates the production of efficient biomass-based catalysts for environmental remediation, but also highlights the application potential of biomass-based carbon nanotubes composites enriched with Co-Nx sites.

The critical roles of surface-bound radicals in the nickel phosphide/biochar-persulfate catalytic oxidation system for tetracycline removal: The synergistic catalysis between nickel phosphides and biochar

Exploring efficient and cost-effective heterogeneous persulfate (PS) oxidation systems is meaningful for addressing recalcitrant organic pollutants in wastewater. Herein, nickel phosphide/biochar (NixP/biochar) composite, with Ni12P5 as the predominant crystalline phase, is firstly synthesized utilizing a biomass phosphorus source, phytic acid (PA). NixP/biochar demonstrates outstanding catalytic capacity in activating PS for removing tetracycline (TC). At 1 mM PS, 0.15 g/L catalyst, and pH 7.0, 94.55 % of TC (20 mg/L) can be removed within 180 min, markedly superior to Fe-, Cu-, and Co-based phosphide/biochar composites. The NixP/biochar-PS system exhibits superior catalytic degradation efficiency (>94.00 %) against varying concentrations (1–20 mg/L) of TC and robustly resists interferences from complex water matrices, including sodium humate solution, surface water, anions (>90.00 %). The ideal catalytic efficiency is ascribed to surface-bound radicals (including SO4-• and •OH), with •O2– and 1O2 assisting in. Density functional theory (DFT) calculations indicate that due to the electron donations from Ni, P, and C, S2O82- may undergo homolysis to produce the surface-bound SO4-•, which may induce the generation of other reactive oxygen species (ROSs) through radical chain reactions. Besides, the electronic structures and work functions of NixP in NixP/biochar composites can be modulated by the biochar, enhancing the catalytic selectivity of NiP, Ni2P, and Ni12P5 with Ni as the electron-donating center, while diminishing that of P-centered Ni3P. These findings may serve as a reference for the theoretical study of Ni-based catalysts and the practical application of NixP in AOPs.

Utilization and value-adding of waste: Fabrication of porous material from chitosan for phosphate capture and energy storage

Efficient removal and recycling of phosphorus from complex water matrices using environmentally friendly and sustainable materials is essential yet challenging. To this end, a novel bio-based adsorbent (DX-FcA-CS) was developed by coupling oxidized dextran-crosslinked chitosan with ferrocene carboxylic acid (FcA). Detailed characterization revealed that the incorporation of FcA reduced the total pore area of DX-FcA-CS to 7.21 m2·g−1, one-third of ferrocene-free DX-CS (21.71 m2·g−1), while enhancing thermal stability and PO43− adsorption performance. Adsorption kinetics and isotherm studies demonstrated that the interaction between DX-FcA-CS and PO43− followed a pseudo-second-order kinetic model and Langmuir model, indicating chemical and monolayered adsorption mechanisms, respectively. Moreover, DX-FcA-CS exhibited excellent anti-interference properties against concentrated co-existing inorganic ions and humic acid, along with high recyclability. The maximum adsorption capacity reached 1285.35 mg·g−1 (∼428.45 mg P g−1), three times that of DX-CS and surpassing many other adsorbents. PO43−-loaded DX-FcA-CS could be further carbonized into electrode material due to its rich content of phosphorus and nitrogen, transforming waste into a valuable resource. These outstanding characteristics position DX-FcA-CS as a promising alternative for phosphate capture and recycling. Overall, this study presents a viable approach to designing environmentally friendly, recyclable, and cost-effective biomaterial for wastewater phosphate removal and value-added applications.

Systematic investigation and modeling prediction of virus inactivation by ozone in wastewater: Decoupling the matrix effects

Water disinfection is undoubtedly regarded as a critical step in ensuring the water safety for human consumption, and ozone is widely used as a highly effective disinfectant for the control of pathogenic microorganisms in water. Although the diminished ozone efficiencies in complex water matrices have been widely reported, the specific extent to which individual components of matrix act on the virus inactivation by ozone remains unclear, and effective methodologies to predict the comprehensive effects of various factors are needed. In this study, the decoupled impact of the intricate water matrix on the ozone inactivation of viruses was systematically investigated and assessed from a simulative perspective. The concept of "equivalent ozone depletion rate constant" (k') was introduced to quantify the influence of different species, and a kinetic model was developed based on the k' values for simulating the ozone inactivation processes in complex matrix. The mechanisms through which diverse species influenced the ozone inactivation effectiveness were identified: 1) competition effects (k' = 105∼107 M–1s−1), including organic matters and reductive ions (SO32−, NO2−, and I−), which were the most influential species inhibiting the virus inactivation; 2) shielding effects (k' = 103∼104 M–1s−1), including Ca2+, Mg2+, and kaolin; 3) insignificant effects (k' = 0∼1 M–1s−1), including Cl−, SO42−, NO3−, NH4+, and Br−; 4) promotion effects (k' = ∼−103 M–1s−1), including CO32− and HCO3−. Prediction of ozone disinfection efficiency and evaluation of species contribution under complex aquatic matrices were successfully realized utilizing the model. The systematic understanding and methodologies developed in this research provide a reliable framework for predicting ozone inactivation efficiency under complex matrix, and a potential tool for accurate disinfectant dosage determination and interfering factors control in actual wastewater treatment processes.

Intensifying electrified flow-through water treatment technologies via local environment modification

Removing high-risk and persistent contaminants from water is challenging, because they typically exist at low concentrations in complex water matrices. Electrified flow-through technologies are viable to overcome the limitations induced by mass transport for efficient contaminant removal. Modifying the local environment of the flow-through electrodes offers opportunities to further improve the reaction kinetics and selectivity for achieving near-complete removal of these contaminants from water. Here, we present state-of-the-art local environment modification approaches that can be incorporated into electrified flow-through technologies to intensify water treatment. We first show methods of nanospace incorporation, local geometry adjustment, and microporous structure optimization that can induce spatial confinement, enhanced local electric field, and microperiodic vortex, respectively, for local environment modification. We then discuss why local environment modification can complement the flow-through electrodes for improving the reaction rate and selectivity. Finally, we outline appropriate scenarios of intensifying electrified flow-through technologies through local environment modification for fit-for-purpose water treatment applications.

Electrocatalytic membrane with p-block bismuth atoms for selective oxygen activation to hydroxyl radicals for effective water decontamination

Herein, individual p-block bismuth (Bi) atoms are dispersed onto N-doped Ti3C2Tx MXene (BiN3/MXene) to enhance the 3e− oxygen reduction reaction (ORR), for the electrosynthesis of hydroxyl radicals (HO•) via the activation of molecular oxygen (O2). Theoretical calculations and experiments reveal that the p-orbitals of Bi atoms can readily hybridize with the p-orbitals of O, which enables the transfer of charges, creates sufficient strength of adsorption for oxygen intermediates, lowers the activation energy, and modulates the rate-limiting reaction. The optimized generation of HO• is up to 26.7 μmol/(L·h·cm2) without additional chemical reagents, facilitating efficient removal of micropollutants from complex water matrices. Specifically, the rate constant (kobs) for sulfamethoxazole degradation achieves 1.027 min−1, outperforming the reported processes for micropollutants removal. This work illuminates the atomic-level construction of a p-block BiN3/MXene electrocatalytic membrane to efficiently perform the 3e− ORR and highlights the substantial potential for wastewater decontamination.

Chitosan derived N-doped carbon anchored Co3O4-doped MoS2 nanosheets as an efficient peroxymonosulfate activator for degradation of dyes

Peroxymonosulfate (PMS), which is dominated by non-free radical pathway, has a good removal effect on organic pollutants in complex water matrices. In this article, a biodegradable cobalt-based catalyst (Co3O4/MoS2@NCS) was synthesized by a simple hydrothermal method with chitosan (CS) as nitrogen‑carbon precursor and doped with Cobaltic‑cobaltous oxide (Co3O4) and Molybdenum disulfide (MoS2), and was used to activate PMS to degrade dye wastewater. Electrochemical tests showed that Co3O4/MoS2@NCS exhibited higher current density and cycling area than MoS2@NCS and MoS2. In the Co3O4/MoS2@NCS/PMS system, the degradation rate of 30 mg·L−1 rhodamine B (RhB) reached 97.75 % within 5 min, and kept as high as 94.34 % after 5 cycles. Its rate constant was 1.91 and 8.37 times that of MoS2@NCS/PMS and MoS2/PMS, respectively. It had good complex background matrices and acid-base anti-interference ability, and had good universality and reusability. The degradation rate of methyl orange (MO) and methylene blue (MB) were more than 91 % within 5 min at pH 4.8. The experimental results demonstrated that MoS2-modified CS as a carrier exposed a large number of active sites, which not only dispersed Co3O4 nanoparticles and improved the stability of the catalyst, but also provided abundant electron rich groups, and promoted the activation of PMS and the production of reactive oxygen species (ROS). PMS was effectively activated by catalytic sites (Co3+/Co2+, Mo4+/Mo5+/Mo6+, CO, pyridine N, pyrrole N, hydroxyl group and unsaturated sulfur), producing a large number of radicals that attack RhB molecules, causing chromophore cleavage, ring opening, and mineralization. Among them, non-free radical 1O2 was the main ROS for RhB degradation. This work is expected to provide a new idea for the design and synthesis of environmentally friendly and efficient MoS2-modified cobalt-based catalysts.

Highly sulfonated hyper-cross-linked polymers as promising adsorbents for efficient and selective removal of ciprofloxacin from water

This study aims at the development of novel and highly sulfonated hyper-cross-linked polymers (sHCPs) using facile and one-step synthetic approach, and verification of the potential applicability of the as-synthesized polymers in the adsorptive removal of various antibiotic pollutants under environmentally relevant conditions. The sHCPs synthesized in this work were capable of highly efficient removal of antibiotic pollutants at relatively high (30 mg/L) and low (50 µg/L) initial concentrations, both from a simple as well as complex water matrices. The rate of ciprofloxacin removal and the adsorption capacity observed for the most efficient adsorbent (qe = 757.7 mg/g) were found to be approximately twice higher than that established for other previously reported sulfonated polymers prepared via post-synthetic sulfonation (qe = 476.9 mg/g), and commercial polymer-based adsorbents (e.g. Amberlyst-15, qe = 438.5 mg/g). The highest adsorption capacity was observed at pH close to neutral for polar antibiotic pollutants that contain protonated functional groups and exist in cationic or zwitterion form (e.g. ciprofloxacin and tetracycline). The reported results clearly imply that highly sulfonated hyper-cross-linked polymers are promising candidates for potential practical application for the elimination of organic pollutants from aqueous media, being capable of selective removal of various antibiotics via ionic interaction even in the presence of a great excess of other cations, anions and organic matter naturally existing in environmentally relevant water samples (e.g. river water).

Highly effective activation of peroxymonosulfate via oxygen-coordinated single-atom iron for water decontamination

The traditional peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) have been significantly limited by the high inputs of oxidants. Herein, an oxygen-coordinated Fe-based single-atom catalyst (Fe-N2O1/OCN) was developed as an efficient pathway to activate peroxymonosulfate (PMS). This catalyst allows for a sharp decrease in PMS dosage while avoiding the release of additional sulfate ions into the treated water. The PAPO generates bisphenol-A (BPA) radicals and SO4•− species adsorbed onto Fe-N2O1/OCN, triggering a chain reaction for BPA degradation through BPA-initiated PAPO. The excellent performance of this system is attributed to the oxygen-coordinated iron center, which weakens the coordination of PMS on Fe-N2O1 and prevents its pre-activation. Furthermore, this PMS activation pathway demonstrates high anti-interference performance and can be continuously conducted in complex water matrices for 20 days, providing a promising alternative to traditional PMS-AOPs.

Insight into the purification of arsenic-contaminated acid water by metal–organic framework MIL-53(Fe) with sulfite: The generation and effect of Fe(IV)

Iron based metal–organic frameworks (Fe-MOFs) have garnered international interest as a novel and promising category of adsorbent materials for the elimination of arsenic from neutral waters. Nevertheless, their practical implementation is constrained by their inadequate adsorption capacity for aqueous arsenite (As(III)), a prevalent arsenic species found in acidic environments such as acid mine drainage. Herein, a novel oxidation-adsorption process to effectively purify As(III)-contaminated water is constructed by combining the MIL-53(Fe) of high acid resistance with sulfite (S(IV)). Notably, the adsorption capacity of the MIL-53(Fe)/S(IV) process for As(III) at pH 3.5 reached 86.4 mg g−1, surpassing the values achieved by MIL-53(Fe) alone by 21.6 times for As(III) and 1.62 times for As(V) (oxidized As(III)). During the oxidation process, MIL-53(Fe) effectively activated S(IV), leading to the formation of the crucial intermediate SO5•−, which then underwent two distinct pathways to respectively generate Fe(IV) and SO4•−, accounting for rapid oxidation of As(III). In the adsorption process, the S(IV) activation (i.e., complexation and electron transfer) on the MIL-53(Fe) surface created additional adsorption sites by dredging the pores and altering the electron cloud distribution within the adsorbent. Furthermore, As(V) trended to form monodentate complexes with surface Fe (e.g., FeOAs bond) in the MIL-53(Fe)/S(IV) process. Notably, this oxidative removal process demonstrated reliable performance in complex water matrices and practical arsenic-contaminated waters. Overall, this study presents a promising strategy to enhance the efficacy of Fe-MOFs for the removal of As(III).

Using waste to treat waste: facile synthesis of hollow carbon nanospheres from lignin for water decontamination.

Lignin, the most abundant natural material, is considered as a low-value commercial biomass waste from paper mills and wineries. In an effort to turn biomass waste into a highly valuable material, herein, a new-type of hollow carbon nanospheres (HCNs) is designed and synthesized by pyrolysis of biomass dealkali lignin, as an efficient nanocatalyst for the elimination of antibiotics in complex water matrices. Detailed characterization shows that HCNs possess a hollow nanosphere structure, with abundant graphitic C/N and surface N and O-containing functional groups favorable for peroxydisulfate (PDS) activation. Among them, HCN-500 provides the maximum degradation rate (95.0%) and mineralization efficiency (74.4%) surpassing those of most metal-based advanced oxidation processes (AOPs) in the elimination of oxytetracycline (OTC). Density functional theory (DFT) calculations and high-resolution mass spectroscopy (HR-MS) were employed to reveal the possible degradation pathway of OTC elimination. In addition, the HCN-500/PDS system is also successfully applied to real antibiotics removal in complex water matrices (e.g. river water and tap water), with excellent catalytic performances.

Assessment of PCR Inhibitor Removal Methods to Monitor Viruses in Environmental Water Samples: DAX-8 Outperforms Competitors

Complex water matrices or viral elution buffers can interfere with the qPCR leading to an underestimation of the potential public health hazards of waterborne viral pathogens. Here, we assessed different approaches to mitigate inhibitory impact of complex water samples during RT-qPCR of murine norovirus (MNV), as an inhibition control. The dilution of extracted samples, the use of qPCR additives, a commercial PCR inhibitor removal kit, and polymeric adsorbents such as Supelite DAX-8 and polyvinylpyrrolidone (PVP) were all investigated in this context. Data indicated that the maximum amplification of MNV by RT-qPCR could be obtained by pre-dilution of samples. However, the dilution factor may depend on inhibitors concentration, primer length, probe sequence, and binding capacity. Interestingly, PCR inhibitor removal kits do not seem to be adequate for removing all PCR inhibitors. In comparison to other approaches studied here, the application of 5% DAX-8 led to an increase in MNV qPCR concentrations. DAX-8 can permanently eliminate humic acids from the extracted nucleic acids from the environmental water samples, and it has the potential to considerably improve the accuracy of the obtained non-detects and measured concentrations by qPCR. Further research is required to understand the performance of polymeric adsorbents with enveloped viruses.

Adsorption of acetochlor-contaminated water systems using novel P-doped biochar: Effects, application, and mechanism

Given the serious threat of acetochlor (ACT) to the aquatic ecological environment, designing wastewater treatment–oriented adsorbents for the sustainable remediation of actual ACT-contaminated water is a promising yet challenging strategy. Herein, a novel P-doped biochar (PBC-800) with a high adsorption capacity (51.34 mg g−1) and a rapid reaction rate (47.35 mg g−1 h−1) for ACT was prepared through pyrolyzing of rice straw biomass pre-impregnated with potassium dihydrogen phosphate (KH2PO4). Additionally, P-doped biochars synthesized at different pyrolysis temperatures exhibited significant variations in ACT adsorption performance, which was mainly ascribed to the distinction between hydrophilicity and sp2 conjugate C (ID/IG = 0.84–1.08). The adsorption behavior of ACT on PBC-800 followed the Elovich kinetics and Freundlich adsorption isotherm models. Thermodynamic calculations indicated that the adsorption of ACT by PBC-800 was a spontaneously disordered decreasing exothermic process. Besides, PBC-800 exhibited a powerful anti-interference for ACT adsorption within complex water matrices, highlighting its potential for various of practical applications. Through characterization analysis and further experiments, it was proved that the excellent adsorption performance of PBC-800 on ACT was ascribed to a combination of physical and chemical adsorption mechanisms, including 57.5% pore filling, 23.4% hydrophobic interaction, 12.7% π–π interaction, and 6.4% hydrogen bonding. Moreover, PBC-800 exerted a prominent adhesion impact upon Gram-positive and negative bacteria at 3 h. This study offers a new idea for the utilization of agricultural residues and provides insights into the mechanism of ACT adsorption through its derived biochar.

Engineered Fe3O4 nanoreactor as a high-performance hydrogen peroxide sensor

Nanozymes with peroxidase-mimicking activities have been extensively explored for hydrogen peroxide (H2O2) detection. However, the conventional nanozyme assay with suspensions suffer the limitations of restricted available surface, loss of short-lived radicals, and slow reaction in non-acidic conditions, thus have a greatly reduced detection sensitivity. We here proposed to overcome these drawbacks by constructing aligned nanoreactor sensor with Fe3O4 nanozymes distributed alongside the nanochannels of anodized aluminum oxide (termed as NR-Fe3O4), which allowed for a spatially confined nanozyme reactions (ca. 5 nm) operated under a filtration reaction mode. We presented the unique merits of NR-Fe3O4 on H2O2 detection compared to Fe3O4 nanozyme suspensions, together with the mechanism discussion about how the radical production and capturing got maximized under the confinement. As a result, our NR-Fe3O4 sensor featured a highly sensitive H2O2 detection with a linear concentration from 10 to 5000 nM (detection limit of 0.9 nM), expanded workable pH to neutral, and enhanced nanozyme stability for at least 8 h continuous run. We further showed the great feasibility of using NR-Fe3O4 sensor in complex water matrices for H2O2 detection, as it allowed for a pore rejection of background organics which in turn protected the internal radicals for a capturing and signal magnification. Our findings highlight the great interest of constructing confinement nanoreactors as an innovative approach of enhancing H2O2 detection sensitivity based on the nanozyme assay.

Rapid and efficient removal of multiple heavy metals from diverse types of water using magnetic biochars derived from antibiotic fermentation residue

Pyrolysis is a promising method to treat antibiotic fermentation residue (AFR), a hazardous waste in China, with the benefits of detoxification and resource recycling. However, the application of the AFR-derived biochar has been limited yet, restricting the use of pyrolysis to treat AFR. Herein, for the first time, we reported the use of magnetic biochars derived from vancomycin fermentation residue to rapidly and efficiently co-adsorb multiple heavy metals from diverse types of water with complex matrices. The biochar prepared at 700 °C (labeled as VBC700) exhibited high affinity and selectivity for multiple heavy metals, especially for Ag(I), Hg(II), Pb(II), and Cu(II). The kinetics for Ag(I), Hg(II), and Pb(II) were ultrafast with an equilibrium time of only 5 min, while those for Cu(II) were relatively slower. The maximum adsorption capacity calculated from the Langmuir model for Ag(I), Hg(II), Pb(II), and Cu(II) reached 177.4, 105.9, 387.1, 124.5 mg/g, respectively, which were superior to much previously reported adsorbents. Impressively, Na(I), K(I), Ca(II), Mg(II), and salinity did not affect the capture of these heavy metals, and thus >99% of Ag(I), Pb(II), and Cu(II) were concurrently removed from complex water matrices including seawater, which has rarely been reported before. Furthermore, VBC700 remained high adsorption performance at pH ≥ 3. The adsorption mechanisms included ion exchange, precipitation, and inner-sphere complexation. Overall, the results demonstrate that VBC700 would be an excellent adsorbent to co-capture multiple heavy metals from diverse types of water, highlighting the feasibility of using pyrolysis to achieve a win-win goal for AFR management and heavy metal pollution control.

Peroxymonosulfate conversion to singlet oxygen over π-electron delocalized carbon nitride for selective degradation of emerging contaminants

Graphitic carbon nitride is a promising catalyst for peroxymonosulfate (PMS) activation towards removal of emerging contaminants in water environment. However, the dependence on light and the non-selectivity of PMS activation pathway limit its practical applications. In this work, a two-step thermal treatment process was developed to modulate the π-electron delocalization degree of carbon nitride. The obtained modified carbon nitride (TCN) showed excellent capability on PMS activation without light, and simultaneously achieved high selectivity on the generation of non-radical species 1O2. Based on the results of quenching and probe experiments, isotopic solvent effect, as well as in-situ capture technique, the dominant contribution of 1O2 to the degradation of pollutants was clarified. The TCN/PMS system showed highly selective degradation of electron-donating pollutants, further demonstrating the dominant role of 1O2. Combining the control experimental results, PMS was speculated to be catalytically activated mainly through the spontaneous decomposition pathway. Further, according to the characterizations results and density functional theoretical calculations, it was the delocalized π-electrons at modified C-N heterocycles that accelerated the self-decomposition reactions of PMS. The high selectivity towards 1O2 endowed good resistance of TCN/PMS system in complex water matrices, achieving efficient removal of a number of emerging contaminants.

Trace Organic Contaminant Removal from Municipal Wastewater by Styrenic β-Cyclodextrin Polymers.

Trace organic contaminants (TrOCs) present major removal challenges for wastewater treatment. TrOCs, such as perfluoroalkyl and polyfluoroalkyl substances (PFAS), are associated with chronic toxicity at ng L-1 exposure levels and should be removed from wastewater to enable safe reuse and release of treated effluents. Established adsorbents, such as granular activated carbon (GAC), exhibit variable TrOC removal and fouling by wastewater constituents. These shortcomings motivate the development of selective novel adsorbents that also maintain robust performance in wastewater. Cross-linked β-cyclodextrin (β-CD) polymers are promising adsorbents with demonstrated TrOC removal efficacy. Here, we report a simplified and potentially scalable synthesis of a porous polymer composed of styrene-linked β-CD and cationic ammonium groups. Batch adsorption experiments demonstrate that the polymer is a selective adsorbent exhibiting complete removal for six out of 13 contaminants with less adsorption inhibition than GAC in wastewater. The polymer also exhibits faster adsorption kinetics than GAC and ion exchange (IX) resin, higher adsorption affinity for PFAS than GAC, and is regenerable by solvent wash. Rapid small-scale column tests show that the polymer exhibits later breakthrough times compared to GAC and IX resin. These results demonstrate the potential for β-CD polymers to remediate TrOCs from complex water matrices.