Synthetic Water Research Articles

Kinetic, Isothermal and Thermodynamic Study on the Removal of Hexavalent Chromium with Biocomposites (Cellulose–PLA)

Currently, water is being polluted via various anthropogenic activities, resulting in wastewater contaminated with multiple pollutants, including heavy metals. Hexavalent chromium is a toxic heavy metal that poses significant health risks upon exposure. Biocomposites are materials that are partially composed of organic substances that enhance different properties of a composite. The aim of this study was to evaluate the kinetic, isothermal, and thermodynamic behaviour of a cellulose-based biocomposite with polylactic acid (PLA) for the removal of Cr (VI) from synthetic water. The results indicated that the Freundlich and Elovich models provided the best fit for the isothermal and kinetic data, with R2 values of 0.671 and 0.973, respectively, suggesting that the adsorption process was chemical in nature and occurred on a heterogeneous, multilayer surface. Additionally, the thermodynamic analysis revealed that the adsorption process was exothermic, irreversible, and non-spontaneous. This study presents an innovative approach to the removal of metal ions using a cellulose–PLA biocomposite for wastewater treatment, offering kinetic, isothermal, and thermodynamic data applicable to the adsorption of other heavy metals.

Reactive carbon capture using saline water: evaluation of prospective sources, processes, and products.

Reactive carbon capture (RCC) processes involve the capture of carbon dioxide (CO2) and conversion to a value-added product using a single sorbent/reaction medium. Not only can RCC processes generate valuable byproducts that can reduce the cost of carbon capture, but RCC tends to have lower energy demand than processes involving the transfer of CO2 between the mediums used for capture and subsequent reactions. Saline water has been proposed as a potential medium for RCC due to it's relative abundance and low cost. Additionally, the composition and chemistry of many saline water sources: (1) elevates the CO2 content (as compared to atmospheric concentrations), (2) provides various cations that can form valuable products with CO2, and (3) enhances the kinetics of chemical reactions used to convert CO2 to stable byproducts. In addition to established industrial processes for converting CO2 into inert or valuable byproducts, we found 20 new processes and technologies that have been developed specifically to capture and convert CO2 using saline water. Both preexisting and emerging processes can be broadly classified as electrochemical or chemical titration processes. When assessing the potential viability of applying any of these processes for large scale carbon capture, several factors must be considered, such as the net carbon footprint of the process, the market size, location of customers and value of the end product, the energy demand and chemical costs of the process, and any other environmental impacts. The feasability of many emerging saline-based RCC processes is difficult to determine, as many technologies were tested using synthetic saline waters and/or concentrated CO2 sources. Notwithstanding the early stage of development of many saline-based RCC technologies, the major limitation to implementation of this approach to carbon capture is the mismatch in the scale of the markets for products of saline-based RCC and the scale of carbon capture needed to meet climate goals. However, because the products of many of the processes reviewed here are stable and non-hazardous, these technologies may also be used for carbon sequestration efforts where the products are managed as waste, in which case the carbon capture potential of these technologies can surpass the market-imposed limitations on RCC. Thus, the potential benefits of saline water-based RCC identified in this review encourage further study and development of these technologies.

Green synthesis and enhanced photocatalytic performance of Co-Doped CuO nanoparticles for efficient degradation of synthetic dyes and water splitting

Green synthesis and enhanced photocatalytic performance of Co-Doped CuO nanoparticles for efficient degradation of synthetic dyes and water splitting

Retraction notice to "Photocatalytic degradation of organic synthetic dyes and textile dyeing waste water by Al and F co-doped TiO2 nanoparticles" [Environ. Res. 206 (2022) 112492

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. By changing the contrast and brightness, it appears that the various EDX spectra in Figure 5 show signs of being edited at several areas and are likely to originally be the same spectrum. Furthermore, the FTIR spectrum (Figure 2) in the original version showed signs of manipulation and this was removed and replaced with other FTIR spectra in the revised/published version. The corresponding author was contacted for comment about these concerns but failed to respond. The Editors have therefore lost confidence in the reliability of the findings presented in this article as a whole, and are retracting it. Unauthorised authorship changes were made when the revised version of this paper was submitted, following suggestions for relatively minor revisions from the reviewers and Guest Editor, with authors Mansour K. Gatasheh, Ashraf Atef Hatamleh and S.Ilavenil being added to the paper. No explanation was given for this change, nor was it approved by the editor. This authorship change breaches the policies of the journal and as a result, the editors no longer have confidence in the contributions of the authors in this paper and are retracting it. The journal apologises for not having identified the problematic authorship change during the review process and for any resulting inconvenience.

Retention of Nickel and Cobalt in Boda Claystone Formation

The Boda Claystone Formation (BCF) is considered to serve as a natural barrier to the potential high-level radioactive waste repository in Hungary. In order to evaluate the radionuclide retention capacity of the albitic claystone of the BCF, the adsorption and diffusion properties of the rock for Ni2+ and Co2+ cations (activation products) were investigated separately and in competitive conditions when the two ions were simultaneously added. Batch sorption experiments were performed with powdered and conditioned albitic claystone samples in synthetic pore water to obtain adsorption isotherms. In addition, adsorption tests were performed on petrographic thin sections to check the transferability between dispersed and compact systems. Correlation analysis of microscopic X-ray fluorescence elemental maps recorded on thin sections suggested that nickel is primarily bound to clay minerals (mainly illite and chlorite), which was confirmed by (scanning) transmission electron microscopy measurements. Around illite particles, a newly formed nickel-rich few atomic layer thick phyllosilicate phase was identified. The discrepancy between the experimental and modeled adsorption isotherm at high concentrations could be explained with this nickel-rich new phase. Apart from Cin = 10−3 M and only Ni2+ or Co2+ in the source, the apparent diffusion coefficients of Ni2+ and Co2+ (Cin = 10−3–10−2 M) were found to be similar. Overall, the BCF shows promising capabilities to retain the studied radionuclides.

Freeze-Casting of Mining Wastes for Developing Sustainable Self-Supporting Ceramic Membranes

In this work, kaolin processing waste (KW) and columbite–tantalite waste (CTW) from mining activities were used to manufacture sustainable self-supporting ceramic membranes using the freeze-casting technique. The wastes were characterized, and formulations using only wastes were developed. Gelatin was used in the freeze-casting as a processing aid to avoid dendritic or lamellar pores. The membranes were sintered at different temperatures (1100 °C, 1200 °C and 1300 °C) and analyzed by X-ray diffraction, scanning electron microscopy, flexural strength measurement, and mercury porosimetry. The flux through the membranes was measured using a gravity-driven dead-end filtration system. The membranes containing 80% KW and 20% CTW sintered at 1200 °C showed high porosity (59%), a water permeate flux of 126.5 L/hm2, and a mechanical strength of 1.5 MPa. Filtration tests demonstrated effective turbidity removal (>99%) for synthetic water consisting of tap water and bentonite, reaching 0.1 NTU. The use of mining waste has shown considerable promise for the development of sustainable and affordable membranes for water treatment applications.

Enhanced iodinated disinfection byproducts formation in iodide/iodate-containing water undergoing UV-chloramine sequential disinfection: Machine learning-aided identification of reaction mechanisms.

Restricted to the complex nature of dissolved organic matter (DOM) in various aquatic environments, the mechanisms of enhanced iodinated disinfection byproducts (I-DBPs) formation in water containing both I- and IO3- (designated as I-/IO3- in this study) during the ultraviolet (UV)-chloramine sequential disinfection process remains unclear. In this study, four machine learning (ML) models were established to predict I-DBP formation by using DOM and disinfection features as input variables. Extreme gradient boosting (XGB) algorithm outperformed the others in model development using synthetic waters and in cross-dataset generalization of surface waters. Shapley additive explanation (SHAP) analysis, partial dependence plots (PDPs), and individual conditional expectation (ICE) analysis were then employed to explain the models' workings and feature interactions, aiding in identification and quantification of underlying mechanisms. A type of DOM component (namely DC_b) was found as the greatest contributor and identified as reduced quinones associated with broken-down lignin within higher plant-derived fulvic substance, serving as precursors and electron shuttles for I-DBP formation. Based on the interactional effects acquired from explanation results, the ejection of e-aq from excited DOM and pre-existing I- in the I-/IO3- system were identified responsible for the enhanced generation of I-DBPs compared to that in the I- or IO3- alone systems; extra DOM scavenged reactive iodine species (RIS), contributing to a limited enhancement. These findings and the methodology developed here together enhance our understanding of the mechanisms how DOM limitedly promotes I-DBP formation during UV-chloramine sequential disinfection of I-/IO3--containing water and facilitate effective online monitoring in the future.

Reuse of End-of-life Seawater Reverse Osmosis (RO) Membranes for Water Treatment

Due to the continuing growth in RO desalination plants and the finite lifespan of the RO membranes, large stocks of the end-of-life (EoL) RO membranes are discarded to landfills. This has become a critical challenge in the RO desalination industry. The overall objective of this study was to validate the possibility of direct reuse of the end-of-life seawater reverse osmosis membranes (EoL SWRO) for brackish water desalination in order to limit the environmental impact of their disposal. This study investigates the membrane performance and characterization of four SWRO modules (EoL-M1, EoL-M2, EoL-M3, and EoL-M4). The hydraulic performance of the old membranes was assessed using 5,000 ppm synthetic (NaCl) brackish water and real brackish water, and was compared with the performance of two commercial membranes, namely brackish water RO membrane (BW30) and nanofiltration membrane (NF90). 84-92% NaCl rejection was achieved by direct reuse of EoL membranes, which was higher than the rejection characteristics obtained using commercial BW30 and NF90 membranes. Removal of common salts represent in natural water sources (Na2SO4, Mg2SO4 and MgCl2) and humic substances was also investigated using EoL membranes. The rejection of Na2SO4, MgSO4 and MgCl2 salt solutions was in the range of (50.0-85.8%) with a highest rejection value was obtained for Na2SO4 and the lowest rejection was observed for MgCl2 solution, while a complete rejection was achieved for humic acid. Salt rejection of real brackish water filtration by the EoL membranes (75-77%) presented NF-like properties (Salt rejection was obtained for NF90 membrane was 77%). Therefore, the potential of reusing EoL SWRO is promising and thus benefit the desalination industry and the environment in Oman.

Full-grid bathymetry estimation in the numerical simulation of 8 tidal constituents using an ensemble adjustment Kalman filter-smoothing scheme

The spatially varying geographic-parameters introduce significant uncertainty into the ocean model. Due to the impracticality of manually tuning spatial varying parameters, data assimilation methods are widely used for geographic-parameter optimization (GPO). Practically, the limited observations do not contain enough information to perform GPO directly on the entire grid. Therefore, techniques are required to reduce the complexity of the parameters. A full-grid GPO scheme based on the ensemble adjustment Kalman filter (EAKF) is developed. Via smoothing the spatial distribution of posterior parameter members, the EAKF-smoothing (EAKF-S) introduces additional spatial correlations among parameters. Meanwhile, the small-scale correlation between the state and the parameters, which exhibit strong pseudo-correlations, is filtered out. A tide model of the Bohai Sea and Yellow Sea, considering 8 principal tidal constituents. is constructed using the Princeton Ocean Model with the generalized coordinate system (POMgcs). The EAKF-S is employed for optimizing the full-grid bathymetry. In twin experiment, based on idealized water level observations, EAKF-S effectively reduced model errors and approximately inverted the “true” bathymetry. After GPO, the lowest mean absolute error of the parameter ensemble is 0.83 m. A series of practical GPO experiments based on synthetic water level observations calculated from NAO.99Jb data are performed. First, the improvement of EAKF-S in accuracy and efficiency over standard EAKF is proven using an M2 tide model. After that, a practical experiment on an 8 constituents tide model is performed. The results show that the forecasting performance of all 8 constituents is improved after GPO, indicating the efficacy of EAKF-S.

Invisible Peril: Assessing microplastic pollution in Ghanaian mangroves

Mangroves are key providers of crucial ecological services. This study's aim is to investigate the levels of microplastic (MP) contamination in mangroves from Ghana's Western and Central regions. A total of 1303 particles were analysed from sediment and water samples, 65 % comprising MPs. West and Central regions had notable differences in MPs abundance. Sediment had the highest number of MPs (703 MPs), with concentrations ranging from 0.01 to 2.23 MPs/g·dw, whilst concentrations in water ranged from 0.2 to 3.75 MPs/l. Fibre shapes were the most abundant MP (67 %) followed by fragments. Ten different groups of polymers were found, with polyester, polyethylene and polypropylene being the most abundant. Synthetic hair, textile and water sachets/small plastic bags were expected to be the source of most MPs collected. High population abundance was shown to be related to high levels of MPs. Our findings suggest reducing single-use plastics, waste management/treatment, and clean drinking water, could reduce the impact of MPs in Ghana.

Removal of carbendazim by sorption onto a continuous fixed bed hybrid filter of calcined clay and waste derived biochar

This study focused on enhanced Carbendazim (CBZ) removal by using dual filter media of calcined clay (CC) and biochar (WB-BC) in a continuous fixed-bed column. The experiments were carried out using synthetic and real water. In the continuous system with an initial CBZ concentration of 0.2 mmol L−1, a flow rate of 4 mL min−1, a bed depth of biochar 1 cm and a pH of 6.8, the optimal values for the mass transfer zone (0.64 cm) and adsorption capacity (0.38mmolg−1) were observed. Furthermore it was observed that the dual filter media of WB-BC and CC effectively adsorbs CBZ from real water matrix, with an average adsorption capacity of 0.33mmolg−1. Significant reduction in the concentrations of chlorides, sulfates, nitrates, Ca2+, and Mg2+ were also observed in real water samples along with CBZ removal. Analysis using mass-transfer models showed that BDST model effectively described the breakthrough curve data. Density Functional Theory (DFT) calculations revealed that WB-BC exhibits a stronger interaction and higher adsorption capacity for CBZ compared to CC as evidenced by a shorter vertical distance (2.711 Å) and higher adsorption energy value (−42.95kJmol−1) in case of WB-BC-CBZ complex. Additionally, the larger band gap (ΔE) value (2.881 eV) for WB-BC-CBZ complex indicates superior structural stability and chemical hardness.

Lead removal by its precipitation with biogenic sulfide in a membrane biofilm reactor

We evaluated the feasibility of using hydrogen (H2)-based membrane biofilm reactors (MBfRs) to promote the growth of hydrogenotrophic sulfate-reducing bacteria (SRB) to remove lead (Pb) through its precipitation as lead sulfide (PbS) via biogenic sulfide (HS−) production. Two MBfRs (R1 and R2) were set-up to treat synthetic water rich in sulfate (SO42−) (585 mg/L) and Pb (50, 100, or 250 mg/L). R1 had one influent that had the Pb and synthetic media mixed together; R2 received the Pb solution and synthetic medium through separate influent lines. Oxygen (O2) and nitrate (NO3−) were secondary electron acceptors in R1 and R2, respectively. R1 and R2 produced enough HS− (> 73 mg/L) to precipitate Pb, and Pb removal reached >97 %. Chemical equilibrium calculations identified which solids were possible in each stage of operation. Precipitation of Pb with phosphate (PO43−) occurred in the feed solution in R1, but phosphate precipitation was avoided in the R2 influent. The predominant Pb precipitate inside R2 was PbS, which was confirmed by SEM-EDX analysis. The microbial communities of R1 and R2 were dominated by two SRB – Desulfomicrobium and Fusibacter – along with sulfur oxidizer Thiovirga and denitrifier Thauera. Although the presence of electron acceptors other than SO42− enabled other respiratory metabolisms, they did not prevent SO42− reduction to HS− or the precipitation of PbS.

Adsorption of Cr(VI) Using Organoclay/Alginate Hydrogel Beads and Their Application to Tannery Effluent.

The tanning industry is among the most environmentally harmful activities globally due to the pollution of lakes and rivers from its effluents. Hexavalent chromium, a metal in tannery effluents, has adverse effects on human health and ecosystems, requiring the development of removal techniques. This study assessed the efficacy of organobentonite/alginate hydrogel beads in removing Cr(VI) from a fixed-bed adsorption column system. The synthesized organobentonite (OBent) was encapsulated in alginate, utilizing calcium chloride as a crosslinking agent to generate hydrogel beads. The effects of the volumetric flow rate, bed height, and initial Cr(VI) concentration on a synthetic sample were analyzed in the experiments in fixed-bed columns. The fractal-like modified Thomas model showed a good fit to the experimental data for the asymmetric breakthrough curves, confirmed by the high R2 correlation coefficients and low χ2 values. The application of organoclay/alginate hydrogel beads was confirmed with a wastewater sample from an artisanal tannery industry in Belén (Nariño, Colombia), in which a Cr(VI) removal greater than 99.81% was achieved. Organobentonite/alginate hydrogels offer the additional advantage of being composed of a biodegradable polymer (sodium alginate) and a natural material (bentonite-type clay), resulting in promising adsorbents for the removal of Cr(VI) from aqueous solutions in both synthetic and real water samples.

CO2 Foamed Viscoelastic Gel-Based Seawater Fracturing Fluid for High-Temperature Wells.

This study investigates the development of a novel CO2-foamed viscoelastic gel-based fracturing fluid to address the challenges of high-temperature formations. The influence of various parameters, including surfactant type and concentration, gas fraction, shear rate, water salinity, temperature, and pressure, on foam viscosity was systematically explored. Rheological experiments were conducted using a high-pressure/high-temperature (HPHT) rheometer at 150 °C and pressures ranging from 6.89 to 20.68 MPa. To simulate field conditions, synthetic high-salinity water was employed. The thermal stability of the CO2 foam was evaluated at a constant shear rate of 100 1/s for 180 min. Additionally, foamability and foam stability were assessed using an HPHT foam analyzer at 100 °C. The results demonstrate that liquid phase chemistry, experimental conditions, and gas fraction significantly impact foam viscosity. Viscoelastic surfactants achieved a peak foam viscosity of 0.183 Pa·s at a shear rate of 100 1/s and a 70% foam quality, surpassing previous records. At lower foam qualities (≤50%), pressure had a negligible effect on foam viscosity, whereas at higher qualities, it increased viscosity by over 30%. While a slight increase in viscosity was observed with foam qualities between 40% and 60%, a significant enhancement was noted at 65% foam quality. The addition of polymers did not improve foam viscosity. The generation of viscous and stable foams is crucial for effective proppant transport and fracture induction. However, maintaining the thermal stability of CO2 foams with minimal additives remains a significant challenge in the industry. This laboratory study provides valuable insights into the development of stable CO2 foams for stimulating high-temperature wells.

Data-Informed Synthetic Networks of Water Distribution Systems for Resilience Analysis in Puerto Rico

The increasing potential of infrastructure disruptions calls for high-quality infrastructure models to be used in resilience analysis and decision making. Unfortunately, many utilities and communities do not have access to accurate and detailed models due to a lack of data and resources. Furthermore, security restrictions on sharing infrastructure models present roadblocks to research, analysis, and decision making. Recent advances in the development of synthetic water distribution models provide a potential solution to this problem. There is an opportunity to improve these methods by leveraging incomplete pipe datasets to aid synthetic network generation. To address this gap, we developed a methodology for synthetic network generation that incorporates partial pipe data using a modification of the minimum cost flow algorithm for network generation and pipe sizing. This methodology demonstrates how partial pipe data can be leveraged to improve site-specific synthetic network generation. For the study area of Mayagüez, Puerto Rico, a synthetic model generated using 50% of real pipe data matches the pressure of the validation system with an average error of 23.5 m of head, which improves upon the average error of 31.6 m of head produced by a synthetic model generated using no data of the real pipes. Additionally, synthetic networks are shown to replicate the pressure response under a disruption scenario of the validation network, suggesting potential use in resilience analysis.

Fe3O4 nanoparticles decorated on N-doped graphene oxide nanosheets for elimination of heavy metals from industrial wastewater and desulfurization

Finding an effective and excellent pertinent single catalyst material for multipurpose application for the purification of hydrocarbons in fuels (desulfurization), and for efficient removal of heavy metals from industrial effluent is greatly endowed. In the present work, a hybrid nanocomposite of ultrafine magnetite (Fe3O4) nanoparticle embedded on the surface of in-situ nitrogen doped layered GO (NGO) sheets were fabricated by sol-gel method and treatment with microwave irradiation technique is reported for the first time. The results show a high removal efficiency of 97 % for multiple heavy metals (Pb2+, Cd2+, Cu2+, Cr+2, Mn+2etc.) in industrial effluent and as well as in synthetic water with a very good retention performance of 99 %. The composites were tested against the elimination of sulfur from thiophene is 1.495 mmol g−1 is reported high is due to coupling and coordination of nitrogen with FeO and C. Recycling studies showed that the developed composites had excellent recyclability, with <82 % removal at the 5th cycle; its feasibility was evaluated using industrial effluent water and in synthetic water. Surface phenomena studies presented here revealed that the adsorptive removal processes of heavy metals involved π electron donor-acceptor interactions, ion exchange, and electrostatic interactions, along with surface complexation that showed an excellent synergism. A high stability, and retention performance is better than the pure Fe3O4 and NGO sheets. We hope that this study will motivate and give further scope for scientists working on magnetite-based graphene nanocomposites.

Filtro empacado con residuos de lodos de Al para la eliminación de fósforo como sistema de pulimento en una planta de tratamiento de aguas residuales

Recently, using residual aluminum sludge (Al-sludge) from drinking water treatment plants for phosphorus removal has been assessed and it has shown to be highly efficient. However, most of the studies have been conducted using synthetic water. Only a few works have applied this method to real wastewater (WW), and none of them have been tested in continuous mode, as a polishing step, in a pilot-scale, decentralized wastewater treatment plant (WWTP). This paper aimed to evaluate the performance of an immersed filter packed with a bed of residual Al-sludge as a polishing system for Phosphorous removal, in a pilot-scale, decentralized WWTP. The study determined at laboratory-scale the capacity for phosphorus removal through batch and continuous tests using both synthetic and real wastewater and evaluated the effect of retention time. Based on the results, an Al-sludge immersed filter (Al-sludge Filter) at pilot-scale was constructed, implemented, and evaluated as a polishing step for the effluent of a decentralized-WWTP. The results showed that during continuous testing with real WW, the phosphorus removal capacity was 2.55 mg P-PO43-∙g-1 per gram of Al sludge using a retention time of 120 min. The Al-sludge filter as a polishing system presented an average removal efficiency of 94 ± 8 % and an effluent concentration of under 0.50 mg P-PO43-∙l-1 during the first 20 operational days. For the next 17 days, the system removed 85 ± 9 % on average, showing an effluent concentration of under 1.0 mg P-PO43-∙l-1. From operational day 32 onwards, the removal efficiency was 63.6 ± 10.7 %, with an average effluent concentration of 2.20 ± 0.39 mg P-PO43-∙l-1.

Agitated tank biosorption of ibuprofen using corn cob

The presence of emerging contaminants, especially drugs for human and veterinary use in natural waters, due to their high degree of persistence and the fact that the treatments used in wastewater treatment plants (WWTP) are not efficient at removing them, has been the subject of study by the scientific community. In this work, the removal of ibuprofen from synthetic waters was studied working in an stirred tank using corn cob residues as a biosorbent. Aiming to achieve the highest drug removal rates, several parameters where studied such as: the concentration of biosorbent, the particle size of the biosorbent, the minimum contact time between both adsorbate and biosorbent to reach the equilibrium, the optimum pH and the temperature. The best conditions to remove ibuprofen (20 mg/L) from synthetic water were the use of 15 g/L of corn cobs with a particle size of 0.4191 mm stirring for one hour at pH 6.0. No matter the temperature, a removal rate of 50% was obtained after 10 minutes of contact,reaching an 89% at the equilibrium. A kinetic study showed that the pseudo-second-order kinetic model was the one that best reproduced the experimental data with a determination coefficient (R2) of 0.982, and for the equilibrium behavior, theFreundlich model was the best fit for the adsorption equilibrium data with a R2 of 0.972.

Use of native macrophyte Echinodorus subalatus for grey water treatment applying alternative bed substrate in constructed wetlands

ABSTRACT Two vertical flow constructed wetland (VFCW 1 and VFCW 2) with native macrophyte Echinodorus subalatus (Mart.) were operated. In VFCW 1, the substrates used were ceramic brick, washed sand, seashells (Anomalocardia brasiliana), and ceramic brick and sand in VFCW 2. The system was operated for 74 days, in batches, with cycles of 168 h, and fed with synthetic grey water. The presence of seashells in VFCW 1 was a differential factor (p < 0) for the removal of anionic surfactant (94.09 ± 7.77%), COD (88.43 ± 5.43%) and total phosphorus (45. 98 ± 9.86%) when compared to VFCW 2. The Langmuir isotherm was used to calculate the substrate adsorption capacity for total phosphorus, anionic surfactant, and COD. The results showed that adsorption on support materials was not the primary mechanism of pollutants removal. From 16S sequencing, it was observed that phylum Firmicutes was the most abundant (96.5%), followed by phylum Proteobacteria (3.5%). The results suggest that using seashells as an alternative substrate improved pollutant removal efficiency.

Innovative eco-friendly methyl orange removal: Mechanism, kinetic, and thermodynamic study using starch cryogel-integrated mesoporous silica nanoparticles

This study introduces a novel, eco−friendly composite, uncalcined mesoporous silica nanoparticles incorporated into a starch cryogel (MSNs-Cry), designed for the effective removal of methyl orange (MO) from water. MSNs−Cry integrates uncalcined mesoporous silica nanoparticles (MSNs) within a starch cryogel network, leveraging the high adsorption capacity of MSNs. The composite achieved a maximum adsorption capacity of 18.98 mg g⁻1 and demonstrated high removal efficiencies of 99.00 % ± 0.21 % in synthetic water (10 mg L−1 MO) and 92.77 % ± 1.76 % in real wastewater containing 0.43 mg L−1 MO. The Langmuir isotherm model provided a superior fit (R2 = 0.9930) compared to the Freundlich model (R2 = 0.9180), and the adsorption kinetics followed a pseudo−second−order model (R2 = 0.9917). The primary adsorption mechanisms included electrostatic attraction, hydrophobic interactions, and hydrogen bonding. The process was endothermic (ΔH° = 31.3 kJ mol−1), spontaneous, and more favorable at higher temperatures (ΔG° = −34.2 to −38.6 kJ mol−1 at 298–318 K). In the presence of sodium silicate at 13.1 times the MO concentration, removal efficiency drops by 35.77 %, and with sodium sulfate and urea at 100 times the MO concentration, it decreases by 8.65 %. Despite these challenges, MSNs−Cry effectively removes MO in the presence of the anionic dye Congo Red and metal ions, demonstrating its selective adsorption capabilities. The tablet form of MSNs−Cry prevents the loss of uncalcined MSNs, mitigating potential environmental and operational impacts. Additionally, the composite's effectiveness at a natural pH of 6.65 eliminates the need for pH adjustment, offering a cost−effective solution for real−world applications. This study establishes MSNs−Cry as a promising material for sustainable water purification.