Removal of signal peptide variants by cation exchange chromatography: A case study.

Signal peptide (SP) is required for secretion of recombinant proteins and typically cleaved by signal peptidase at its C-region to generate the mature proteins. Miscleavage of the SP is reported occasionally, resulting in a truncated- or elongated-terminal sequence. In the present work, we demonstrated that cation exchange (CEX) chromatography is an effective means for removing SP variants with a case study. With the selected resin/conditions, the chromatographic performance is comparable between runs performed at the low end and high end of load density and elution range. The procedure described in this work can be used as a general approach for resin selection and optimization of chromatographic conditions to remove byproducts that bind more strongly than the product to the selected resin.

High Efficiency n-Type Doping of Organic Semiconductors by Cation Exchange.

Achieving efficient doping in n-type conjugated polymers is crucial for their application in electronic devices. In this study, an n-type doping method is developed based on cation exchange that maintains a high doping level while ensuring a high degree of structural order, leading to significantly improved electrical conductivity. By investigating various dopants and ionic liquids, it is discovered that the choice of dopant influences doping efficiency, while the selection of ionic liquid affects cation exchange efficiency. Through careful selection of suitable dopants and ionic liquids, High doping levels are achieved remarkably in a short period, resulting in the highest conductivity (nearly 1 × 10- 2 S cm-¹) compared to other doping methods for poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (N2200). The findings highlight the robustness and efficiency of cation exchange doping as an effective approach for achieving high-quality n-type doping in conjugated polymers, thereby opening new avenues for the development of advanced polymer-based electronic devices.

Construction of a triple-mode sensing platform for effective differentiation, speciation, and monitoring of mercury and methylmercury bioaccumulation in crayfish via cation exchange reaction.

Developing rapid and sensitive methods for monitoring inorganic mercury (Hg2+) and methylmercury (CH3Hg+) in crayfish is crucial for understanding the environmental impact of these contaminants. In this work, a novel tri-mode strategy was developed for highly sensitive monitoring of Hg2+ and CH3Hg+ bioaccumulation in crayfish by inductively coupled plasma mass spectrometry (ICP-MS)/ fluorescence /smartphone colorimetric (RGB) analysis without chromatographic separation. Cation exchange reaction (CER) was performed between Hg2+ and luminescent CdTe quantum dots (QDs), while CH3Hg+ unrealizable CER. The CH3Hg+ can be transformed to Hg2+ by simple UV irradiation, speciation analysis can be realized by detecting the fluorescence of CdTe QDs after incubation by Hg2+ and total Hg2+. In addition, the filtration of reacted CdTe QDs was carried out, ICP-MS was performed to detect exchanged Cd2+ by Hg2+ and total Hg2+, as well the smartphone RGB analysis was performed for membrane colorimetry. The limits of detection (LODs) of Hg2+ and CH3Hg+ for ICP-MS, fluorescence, and colorimetric (RGB) modes were 0.03 ng mL-1, 18 ng mL-1, and 0.9 µg mL-1 respectively. Density Functional Theory (DFT) was employed to validate the mechanism of the CER reaction. CdTe QDs array analysis with five different ligands was performed to eliminate potential ion interferences of Ag+ and Cu2+ that could occur during the CER reaction. The well-designed system was successfully utilized for monitoring trace Hg2+ and CH3Hg+ in crayfish fed Hg2+ and CH3Hg+ contaminative food over a two-week "uptake" period and a three-week "depuration" period. The results indicated that the Hg2+ uptake in different tissues was significantly different from that of CH3Hg+ in all tissues. There was evidence of Hg uptake from water via leaching from food, although the principal source of uptake was from food.

Enrichment of deoxynojirimycin in mulberry using cation exchange resin: Adsorption/desorption characteristics and process optimization.

Deoxynojirimycin (DNJ) is an α-glucosidase inhibitor with high food values. However, the complex and costly enrichment processes have greatly prevented its application. Herein, this study aimed to propose a simple and efficient enrichment process for DNJ from Morus alba L. extracts using cation exchange resins. The LSI and D113 resins were chosen due to their excellent adsorption and desorption properties. The adsorption characteristics agreed with the pseudo-first-order kinetic model and the Langmuir isotherm model. This adsorption was chemisorption, spontaneous, endothermic and entropy-driven. Furthermore, the concentration and pH of the extracts, desorption solvent, breakthrough and elution curves, sample loading and elution rate were investigated to optimize the enrichment process by resin column chromatography. The results also showed that the purity of DNJ was improved to 44.00 % with a total recovery of 78.21 % using the LSI-D113 combination strategy. This research demonstrated the industrial feasibility of DNJ enrichment using cation exchange resins.

Hydraulic recharge and element dynamics during salinization in an overexploited coastal aquifer of the world's driest zone: Atacama Desert.

The management of water resources in hyper-arid coastal regions is a challenging task because proper information regarding groundwater recharge and water budget is needed for maintaining the hydraulic balance in optimal conditions, avoiding salinization and seawater intrusion. Thus, this article deals with the estimation of the hydraulic recharge and the study of the effects of salinization on the dynamics of major and trace elements in an alluvial aquifer located in the world's driest zone, the northern Atacama Desert. The result of stable water isotopes (δD and δ18O) and tritium (3H) indicated that groundwater in the area is not recent, whereas 14C results estimated a groundwater residence time ranging between 11,628 and 16,067 yBP. The estimation of the artificial recharge coming from the urban water-supply-system leaks and wastewater/river-water/groundwater infiltration during irrigation was about 19.84 hm3/year, which represents an annual negative water balance of 177 hm3/year for the aquifer. The groundwater salinization triggered by seawater intrusion (up to 32.6 %) has caused the enrichment of Li, Rb, Ca, Ba, and Sr in groundwater by cationic exchange, where the excess of aqueous Na is exchanged by these elements in the aquifer sediments. Other elements such as B, Se, Si, and Sb are enriched in groundwater by ionic strength and/or anionic exchange during salinization. The heightened B concentrations derived from the B-rich alluvial sediments were higher than the limit suggested by international guidelines, representing a risk to consumers. Vanadium seems to be unaffected by salinization, whereas Pb, Mo, As, U, and Zr did not show a clear behavior during saline intrusion. Finally, this article highlights the consequences of conducting improper water management in coastal hyper-arid regions with exacerbated agriculture.

In-depth characterization of a cysteine-linked ADC disitamab vedotin by multiple LC-MS analysis methods and cutting-edge imaged capillary isoelectric focusing coupled with native mass spectrometry.

The characterization of cysteine-linked antibody‒drug conjugates (ADCs) can be more challenging than that of monoclonal antibodies (mAbs) and lysine-linked ADCs because the interchain disulfide bonds are reduced for payload conjugation, and the chains are noncovalently bonded to each other. Furthermore, payload conjugation and disulfide bond reduction/scrambling may introduce additional charge heterogeneity to biomolecules. This study illustrates an innovative workflow employing multiple separation techniques and tandem high-resolution mass spectrometry for comprehensive and in-depth characterization of disitamab vedotin, a recent-generation cysteine-linked ADC, including reversed-phase liquid chromatography (RPLC), ion exchange chromatography (IEX) and image capillary isoelectric focusing (icIEF). RPLC was employed for reduced chains analysis, subunit analysis and peptide mapping. IEX and icIEF were used for charge heterogeneity analysis. The innovation of the integrated methodology emphasizes the importance of cutting-edge icIEF-MS online coupling under near-native conditions to reveal the heterogeneity of disitamab vedotin.

Synthesis and characterization of amine functionalized silylated clay for heavy metal adsorption: Thermodynamic and kinetic studies on Fe(III) ion.

Amine functionalized bentonites were used as adsorbents for the bioremoval of Fe(III) ions, which led to the inclusion of functional groups such as -OH, -NH2, -OCH3, etc. FTIR, XRD, SEM, AFM, TG, BET, XRF, and CHNS analyzer were used to analyze the surface and textural characteristics. The influence of adsorption factors, such as pH, contact time, temperature, and initial concentration, have been investigated and tailored in batch adsorption experiments of Fe (III) metal ions. The maximum adsorption efficiency and capacity of modified BNT-APTMS is 100.90 % and 103.91 mg/g respectively. The adsorption process is best fit with Freundlich model (R2=0.998) than Langmuir model (R2=0.788) and the Temkin model D-R isotherm parameters indicating a physisorption process. A mechanism of spontaneous complexation was accomplished, because of the heterogeneity of the surface, electrostatic forces, pore filling, and π-π stacking. Follows PSO kinetics and favours Freundlich isotherm. The adsorbent substance showed a remarkable capacity for regeneration, assuring the substance's stability and reusability.

Low-Resistance Membrane vs. High-Resistance Membrane Performance Utilizing Electrodialysis-Evaporator Hybrid System in Treating Reject Brine from Kuwait Desalination Plants.

This work is an effort to mitigate the existing environmental issues caused by brine discharge from Kuwait's desalination plants and to find an economical and efficient way of managing reject brine from local desalination plants. Low- and high-resistance membranes (LRMs and HRMs, respectively) were used to produce salt and low-salinity water from brine effluent utilizing an electrodialysis (ED)-evaporator hybrid system. The effect of high current densities of 300, 400, and 500 A/m2 and brine flowrates of 450 and 500 L/h on the quality of produced salt and diluate were investigated for LRM and HRM. The recovered salt purity for LRM is up to 90.58%. Results show that the low-resistance membrane (LRM) achieved higher water recovery, energy consumption, desalination rate, operation time and ion removal rate than those of the high-resistance membrane (HRM) under the same operating conditions. The difference in concentration for 300 A/m2 between LRM and HRM increased from 0.93% at 10 min to 8.28% at 140 min. The difference in diluate concentration effluent is negligible for both membranes, whereas LRM produced higher concentrate effluent than HRM for all current densities and low flowrate (400 L/h). The maximum difference between LRM and HRM (with LRM achieving higher concentrations) is 10.7% for 400 A/m2. The permselectivity of LRM for monovalent cations decreased with current density, whereas the effect on permselectivity for HRM was insignificant for the current density values. The addition of a neutral cell was effective in reducing the buildup of divalent ions on the inner membrane of the cathode side.

Risk of Serious Adverse Gastrointestinal Events with Potassium Binders in Hospitalized Patients: A National Study.

BACKGROUND: Concerns about serious adverse gastrointestinal (GI) events with sodium polystyrene sulfonate (SPS) led to development of two new potassium binders, patiromer and sodium zirconium cyclosilicate (SZC), for treatment of hyperkalemia. OBJECTIVE: To compare risk of intestinal ischemia/thrombosis or other serious GI events associated with SPS, patiromer, or SZC in hospitalized patients. DESIGN: Retrospective cohort study. PARTICIPANTS: National sample of 3,144,960 veterans hospitalized 2016-2022 in the U.S. Department of Veterans Affairs Healthcare System. MAIN MEASURES: Demographics, comorbidities, medications and outcomes were ascertained from the VA Corporate Data Warehouse. Exposures were SPS, patiromer, SZC. Outcomes were 30-day intestinal ischemia/thrombosis, and a composite of intestinal ischemia/thrombosis, peptic ulcer/perforation or bowel resection/ostomy. KEY RESULTS: Potassium binders were used during 39,270 (1.3%) hospitalizations: SPS = 30,040 (1.0%), patiromer = 3,750 (0.1%), and SZC = 5,520 (0.2%). Intestinal ischemia/thrombosis occurred with 106/30,040 (0.4%) SPS, 12/3750 (0.3%) patiromer and 24/5520 (0.4%) SZC, vs. 6998/3,105,650 (0.2%) without potassium binder. Adjusted odds ratios (aOR) were 1.40 [95% CI, 1.16 to 1.69] with SPS, 1.36 [CI, 0.79 to 2.36] with patiromer, and 1.78 [CI, 1.21 to 2.63] with SZC exposures. Composite GI adverse events occurred with 754/30,040 (2.5%) SPS, 96/3750 (2.6%) patiromer, 2.6% SZC, vs. 144/5520 (2.4%) without binder; aOR were 1.00 [CI, 0.94 to 1.08] with SPS, 1.08 [CI, 0.89 to 1.32] with patiromer, and 1.08 [CI, 0.93 to 1.27] with SZC exposures. No statistical difference in intestinal ischemia/thrombosis between each new agent and SPS was seen (p = 0.274 for SPS vs. SZC; p = 0.916 for SPS vs. patiromer). CONCLUSION: Risk of intestinal ischemia/thrombosis or other serious adverse GI events was low and did not differ across three potassium-binding drugs.

Molybdenum Disulfide Induced Phase Control Synthesis of Multi-dimensional Co3S4-MoS2 Heteronanostructures via Cation Exchange.

Phase control over cation exchange (CE) reactions has emerged as an important approach for the synthesis of nanomaterials (NMs). Although factors such as crystal structure and morphology have been studied for the phase engineering of CE reactions in NMs, there remains a lack of systematic investigation to reveal the impact factors in heterogeneous materials. Herein, we report a molybdenum disulfide induced phase control method for synthesizing multidimensional Co3S4-MoS2 heteronanostructures (HNs) via cation exchange. MoS2 in parent Cu1.94S-MoS2 HNs are proved to affect the thermodynamics and kinetics of CE reactions, and facilitate the formation of Co3S4-MoS2 HNs with controlled phase. This MoS2 induced phase control method can be extended to other parent HNs with multiple dimensions, which shows its universality. Further, theoretical calculations demonstrate that Co3S4 (111)/MoS2 (001) exhibits a higher adhesion work, providing further evidence that MoS2 enables phase control in the HNs CE reactions, inducing the generation of novel Co3S4-MoS2 HNs. As a proof-of-concept application, the obtained Co3S4-MoS2 heteronanoplates (HNPls) show remarkable performance in hydrogen evolution reactions (HER) under alkaline media. This synthetic methodology provides a unique way to control the crystal structure and fills the gap in the study of heterogeneous materials on CE reaction over phase engineering.

Cation interception and permeability characteristics of bentonite barriers exposed to NaCl and NH4Cl solutions.

High concentrations of Na+ and NH4+ in landfill leachate lead to deterioration of bentonite barrier and pose a threat to the environment. This study focused on the pollution interception and permeability characteristics of the bentonite barrier exposed to NaCl and NH4Cl solutions. Based on previous findings, salt solution concentrations were established at 74.80, 37.40, 18.70, and 9.4 mmol/L. The bentonite contents in the mixture were set at 0, 5, 10, and 15%. The results indicate that the samples exhibit better interception of NH4+ compared to Na+. This difference arises from the cation exchange sequence, the size of the hydration radius, and the hydrogen bonding of the two cations. Additionally, the difference in hydration enthalpy between the two cations leads to variations in the swelling of bentonite, resulting in a higher hydraulic conductivity coefficient in NH4Cl solution. This study shows that although bentonite barriers have better interception for NH4+, they exhibit greater hydraulic conductivity in NH4Cl solution, increasing the risk of leachate carrying other contaminants.

Effects of Cation Exchange in Rhodamine B Photocatalytic Degradation Using Peroxo-Titanate Nanotubes.

Lepidocrocite-type layered sodium titanate (NaxH2-xTi2O5) is widely used in environmental remediation because of its large specific surface area, formed by anisotropic crystal growth, and its ability to store and exchange cations between layers. Additionally, peroxo-titanate nanotubes (PTNTs), which are tubular titanates with peroxy groups, exhibit visible-light absorption capabilities, rendering them suitable for photocatalytic applications under visible light irradiation. However, because of cation exchange reactions, the Na+ concentration and pH of the solution can fluctuate under aqueous conditions, affecting the photocatalytic performance of the PTNTs. Herein, we evaluated the impact of cation exchange reactions on the photocatalytic degradation of Rhodamine B (Rh B) by PTNTs at controlled Na+ ratios. The observed pH of Rh B solutions increases due to the cation exchange reaction with Na+ and H3O+, leading to the formation of zwitter-ionic Rh B molecules, eventually weakening their adsorption and photodegradation performance. Moreover, the results indicate that inhibiting the pH increase of the Rh B solution can prevent the weakening of both the adsorption and photodegradation performance of PTNTs. This study highlights the significance of regulating the sodium ion content in layered titanate materials, emphasizing their importance in optimizing these materials' photocatalytic efficacy for environmental purification applications.

Characterization of the Charge Heterogeneity of a Monoclonal Antibody That Binds to Both Cation Exchange and Anion Exchange Columns under the Same Binding Conditions.

Therapeutic antibodies play an important role in the public healthcare system to treat patients with a variety of diseases. Protein characterization using an array of analytical tools provides in-depth information for drug quality, safety, efficacy, and the further understanding of the molecule. A therapeutic antibody candidate MAB1 exhibits unique binding properties to both cation and anion exchange columns at neutral pH. This uniqueness disrupts standard purification processes and necessitates adjustments in manufacturing. This study identifies that the charge heterogeneity of MAB1 is primarily due to the N-terminal cyclization of glutamine to pyroglutamine and, to a lesser extent, succinimide intermediate, deamidation, and C-terminal lysine. Using three approaches, i.e., deferential chemical labeling, H/D exchange, and molecular modeling, the binding to anion exchange resins is attributed to negatively charged patches on the antibody's surface, involving specific carboxylic acid residues. The methodologies shown here can be extended to study protein binding orientation in column chromatography.

One-step N-Terminomics Based on Isolation of Protein N-Terminal Peptides From LysargiNase Digests by Tip-Based Strong Cation Exchange Chromatography.

We have developed a one-step isolation method for protein N-terminal peptides from LysargiNase digests by pipette tip-based strong cation exchange (SCX) chromatography. This CHAMP-N (CHromatographic AMplification of Protein N-terminal peptides) method using disposable and parallel-processable SCX tips instead of conventional HPLC SCX columns facilitates simple, sensitive, reproducible, and high-throughput N-terminomic profiling without sacrificing the high identification numbers and selectivity achieved by the HPLC-based method. By applying the CHAMP-N method to HEK293T cells, we identified novel cleavage sites for signal and transit peptides and non-canonical translation initiation sites. Finally, for proteome-wide terminomics, we present a simple and comprehensive N- and C-terminomics platform employing three different tip-based approaches, including CHAMP-N, in which protease digestion and one-step isolation by tip LC are commonly used to achieve complementary terminome coverages.

Synthesis of Sulfur Vacancy-Bearing In2S3/CuInS2 Microflower Heterojunctions via a Template-Assisted Strategy and Cation-Exchange Reaction for Photocatalytic CO2 Reduction.

The synthesis of the accurate composition and morphological/structural design of multielement semiconductor materials is considered an effective strategy for obtaining high-performance hybrid photocatalysts. Herein, sulfur vacancy (Vs)-bearing In2S3/CuInS2 microflower heterojunctions (denoted Vs-In2S3/CuInS2) were formed in situ using In2S3 microsphere template-directed synthesis and a metal ion exchange-mediated growth strategy. Photocatalysts with flower-like microspheres can be obtained using hydrothermally synthesized In2S3 microspheres as a template, followed by Ostwald ripening growth during the metal cation exchange of Cu+ and In3+. The optimal heterostructured Vs-In2S3/CuInS2 microflowers exhibited CO and CH4 evolution rates of 80.3 and 11.8 µmol g-1 h-1, respectively, under visible-light irradiation; these values are approximately 4 and 6.8 times higher than those reported for pristine In2S3, respectively. The enhanced photocatalytic performance of the Vs-In2S3/CuInS2 catalysts could be attributed to the synergistic effects of the following factors: (i) the constructed heterojunctions accelerate charge-carrier separation; (ii) the flower-like microspheres exhibit highly uniform morphologies and compositions, which enhance electron transport and light harvesting; and (iii) the vs. may trap excited electrons and, thus, inhibit charge-carrier recombination. This study not only confirms the feasibility of the design of heterostructures on demand, but also presents a simple and efficient strategy to engineer metal sulfide photocatalysts with enhanced photocatalytic performance.

Multi-decadal geochemical evolution of drainage from underground coal mines in the Appalachian basin, USA.

Coal mine drainage (CMD) in Appalachia is a widespread source of dissolved metals, SO4, and acidity that can degrade aquatic habitats and water supplies for decades following mine closure and flooding. In the bituminous coalfield of Pennsylvania, the Irwin Coal Basin (ICB) contains a series of partly to completely flooded, abandoned underground mines separated by leaky barriers within the Pittsburgh coal seam. CMD originated throughout the basin from minepool aquifers that formed after mine closures dating from 1910 to 1957. Historical and recent water quality data for eight CMD sites across the ICB, plus mineralogy and cation-exchange capacity of overburden lithologies, were analyzed to quantify important reactants and evaluate spatial and temporal water-quality trends. As overburden thickness and residence time increase along a ~ 50-km flowpath northeast to southwest in the basin, CMD becomes more alkaline, and Na concentrations increase. Since the 1970s, all eight ICB discharges have become less acidic, with exponential decreases in acidity, SO4, and Fe concentrations; only two CMD remain net-acidic (acidic pH at equilibrium). Exponential decay models that include a steady-state asymptote consistent with background groundwater chemistry and siderite equilibrium describe the early-stage, rapid contaminant concentration decay immediately after the "first flush" (initial flooding) and the progressive evolution toward late-stage background conditions. A geochemical evolution PHREEQC model indicates that spatial and temporal trends in pH, net-acidity, SO4, Fe, and major cations could be explained by the continuous dilution of first flush water by ambient groundwater combined with sustained water-mineral reactions involving pyrite and carbonates (calcite, dolomite, siderite) plus cation-exchange by clays (illite, chlorite, mixed-layer illite/smectite). These data and model results indicate that 1) cation-exchange reactions enhance calcite dissolution and alkalinity production, resulting in the evolution of CMD to Na-SO4-HCO3 type waters, and 2) siderite equilibrium could maintain dissolved Fe >16 mg/L over the next 40 years.

Mitigation of ammonia volatilization from organic and inorganic nitrogen sources applied to soil using water hyacinth biochars.

The recent global population explosion has increased people's food demand. To meet this demand, huge amounts of nitrogen (N) fertilizer have been applied in the worldwide. However, ammonia (NH3) volatilization is one of the primary factors of N loss from soil after N application causing decrease crop N utilization efficiency and productivity. Incubation experiments were conducted on an acidic clayey soil with two different N sources (urea and anaerobic digestion effluent; ADE), two differently-produced biochars, and three biochar application rates (0%, 0.25%, and 1.0% w/w). Ammonia volatilization was lower from urea (14.0-23.5 mg N kg-1) and ADE (11.3-21.0 mg N kg-1) with biochar application than those without biochar (40.1 and 26.2 mg N kg-1 from urea and ADE alone, respectively). Biochar application significantly mitigated volatilization and reduction percentages for urea and ADE were 40%-64% and 18%-55%, respectively. 1.0% biochar application mitigated volatilization significantly compared to 0.25% application regardless of N source and biochar types. Possible mechanism for volatilization mitigation for urea and ADE were increased N immobilization by soil microorganisms and accelerated net nitrification rate due to increased soil nitrifying bacteria, respectively. Overall, our results clarified different mechanisms for N volatilization mitigation from different (inorganic vs. organic) N sources with biochar application.

Enhancing the properties of swelling soils with lime, fly ash, and expanded polystyrene -A review.

This paper discusses efforts made by past researchers to steady the expansive (problematic) soils using mechanical and chemical techniques - specifically with EPS beads, lime and fly ash. Administering swelling of problematic soils is critical for civil engineers to prevent structural distress. This paper summarizes studies on reduction of swelling potential using EPS, lime and fly ash individually. Chemical stabilization with lime and fly ash are conventional methods for expansive soil stabilization, with known merits and demerits. This paper explores the suitability of different materials under various conditions and stabilization mechanisms, including cation exchange, flocculation, and pozzolanic reactions. The degree of stabilization is influenced by various factors such as the type and amount of additives, soil mineralogy, curing temperature, moisture content during molding, and the presence of nano-silica, organic matter, and sulfates. Additionally, expanded polystyrene (EPS) improves structural integrity by compressing when surrounded clay swells, reducing overall swelling. Thus, EPS addresses limitations of chemicals by mechanical means. Combining EPS, lime and fly ash creates a customized system promoting efficient, long-lasting, cost-effective and eco-friendly soil stabilization. Chemicals address EPS limitations like poor stabilization. This paper benefits civil engineers seeking to control expansive soil swelling and prevent structural distress. It indicates potential of an EPS-lime-fly ash system and concludes by identifying research gaps for further work on such combinatorial stabilizer systems.

New insight into enhanced carbon recovery from anaerobic fermentation of waste activated sludge with cation exchange resin coupled with NaCl pretreatment.

Carbon recovery from waste activated sludge has been attracting considerable attention. However, the migration and transformation patterns of carbon sources between the phases have rarely been reported. In this study, a novel strategy using cation exchange resin (CER) coupled with sodium chloride (NaCl) to enhance carbon recovery through anaerobic fermentation (AF) was proposed. The results demonstrated that CER coupled with NaCl destroyed OH and CO stretching in amide I while promoting the formation of ß-sheet and random coil structures, leading to sludge disintegration. This significantly improved the kinetics of endogenous carbon release, resulting in the release of 1146.33 mg/L of carbon from the solid sludge into the liquid phase. Approximately 75.61 % of the initial carbon source was bio-transformed into short-chain fatty acids. Correspondingly, carbon recovery was significantly increased up to 852.23 mg C/L, 4.57 times that of the control. Mechanism exploration revealed that carbon source recovery was significantly elevated by the synergistic effect of CER and NaCl. CER effectively removed high-valence cations from extracellular polymeric substance (EPS), weakening its bridging and adsorption-electro neutralization capabilities, promoting protein deflocculation, and triggering EPS disruption to release extracellular carbon sources. NaCl disrupted the ionic strength and distribution inside and outside microbial cells, creating an osmotic pressure difference that resulted in cell plasmolysis and lysis, ultimately inducing the release of intracellular carbon sources. Economic and carbon emission reduction benefit analyses verified that the CER coupled with NaCl pretreatment is a cost-effective sludge treatment strategy. This study illustrates the carbon source migration and transformation pathways in the CER coupled with NaCl-assisted AF process, providing guidance for sustainable sludge management.

Recycling aluminum from polyaluminum chloride sludge through acid dissolution and cation resin separation/purification.

To recycle aluminum (Al) from waterworks sludge resulting from polyaluminum chloride (PAC) used as coagulants, this study proposed an innovative strong acidic cation (SAC) exchange resin treatment strategy for Al separation from coexisting fulvic acid (FA) and heavy metals (HMs) in the H2SO4 leachate of PAC sludge. Fluorescence titration confirmed the breakdown of the Al-FA complex at pH 2.0, which facilitated Al separation from FA in the acidic leachate. The species distribution of the dissociated Al (i.e. Ala, Alb, and Alc) significantly influenced the adsorption of Al onto the cation exchange resin. The continuous release of H+ during the cation exchange reaction greatly promoted the transformation of dissociated Alc and Alb into Ala, thereby improving the adsorption of total Al. Moreover, the SAC resin column successfully separated the codissolved HMs from the Al in the leachate even at an influent pH of 2.8, which was attributed to the greater selectivity of the sulfonate groups on the cation exchange resin for free Al3+. The Al eluted from the exhausted resin with 1.1 M H2SO4 was collected as the recycled coagulant after proper pH adjustment. The Al adsorption capacity of the SAC resin decreased by approximately 5 % with each operation cycle and was regained by complete regeneration with 1.8 M H2SO4 after 5 cycles. Overall, the integrated efficiency of Al recovery from PAC sludge by H2SO4 acidification and SAC resin separation/purification reached 70.10 %. The recycled Al from sludge has a water treatment performance comparable to that of fresh PAC coagulant.