Regeneration and reusability of non-conventional low-cost adsorbents to remove dyes from wastewaters in multiple consecutive adsorption–desorption cycles: a review

Crosslinked chitosan-benzil/microalgae/kronos (titanium dioxide) biocomposite for the removal of brilliant green dye: Response surface methodology optimisation and mechanism

In this study, the adsorptive performance of the hydrothermally crosslinked Chitosan- Benzil/Microalgae/Kronos (TiO2) (Cs/Bz2-Ma-KT) biocomposite was evaluated towards removal of brilliant green (BG) a toxic cationic dye. Box-Behnken-Design from Response Surface Methodology (BBD-RSM) was employed for the design of the experiments, statistical analysis of the variables affecting the adsorption process, and finally for the optimisation of the adsorption parameters. The results revealed that the pH of the adsorption environment has the highest impact on the removal of BG dye due to the electrostatic repulsion and attraction occurring in pH values lower and higher than pHpzc of the adsorbent, respectively. The synthesised Cs/Bz2-Ma-KT exhibited a specific surface area of 1.32 (m2/g) with a pore diameter of 34.42 (nm; pore volume = 0.11 cm3/g) and was categorised as a mesoporous material. The adsorption equilibrium studies revealed that the adsorption of BG dye by Cs/Bz2-Ma-KT happens in a monolayer fashion (best compatibility with the Langmuir isotherm model; R2 = 0.93), while the adsorption process mainly occurs through chemisorption (better compatibility with the PPSO kinetic model). Furthermore, the maximum monolayer adsorption capacity of Cs/Bz2-Ma-KT was found to be 289.2 mg/g, exhibiting a great potential to be employed for the removal of BG dye from effluents. Moreover, the thermodynamic parameters revealed the spontaneity and feasibility of the adsorption process due to the negative values of ΔG, whereas the positive ΔH value signified the endothermic nature of the adsorption process.

Advances in perovskite membranes for carbon capture & utilization: A sustainable approach to CO2 emissions reduction - A review

Despite agreements like the Paris Agreement, the world continues to face rising temperatures, extreme weather, and ecosystem disruptions, driven by continued use fossil fuel, agricultural emissions, and industrial activities and leading to greenhouse gas contributing to the serious fuelling climate change. Carbon capture and utilization (CCU), particularly thermochemical carbon dioxide (CO2) splitting powered by thermal energy, offers a promising solution. Perovskite-based inorganic membranes, known for their high selectivity and permeability toward various gases, efficiency, and energy-saving potential, have attracted significant interest in gas separation, production and emerged as a leading technology for carbon capture and hydrogen purification. This review explores advancements in perovskite materials, focusing on H2/CO2 separation, CO2 conversion to CO, and optimal operating conditions. It addresses key questions such as improving material performance through innovations in double and composite perovskites, enhancing oxygen removal via thermochemical or electrochemical pumps, and integrating CO2 splitting with fuel production. These strategies aim to reduce costs, boost efficiency, and provide sustainable pathways for addressing climate change.

Isotherm, kinetic, thermodynamic, and reusability studies of oil palm EFB-derived activated carbon for leachate treatment

Municipal solid waste (MSW) leachate poses significant environmental challenges due to its high concentrations of organic and inorganic pollutants. This study investigates the adsorption efficiency of activated carbon derived from oil palm empty fruit bunches (EFBAC) for landfill leachate treatment. EFBAC was synthesized via physical activation, involving carbonization at 450 °C and activation at 800 °C under limited air conditions. Batch adsorption experiments evaluated the effects of contact time, adsorbent dosage, pH, and temperature on the removal of chemical oxygen demand (COD), ammoniacal nitrogen (AN), and color. Optimal conditions achieved maximum removal efficiencies of 72.1% for COD, 57.5% for AN, and 69.0% for color. Isotherm analysis identified the Sips, Dubinin-Radushkevich, and Koble-Corrigan models as the best fits for COD, AN, and color, respectively. Kinetic studies indicated a pseudo-second-order mechanism, highlighting chemisorption as the rate-limiting step, while thermodynamic evaluation confirmed the process as spontaneous and endothermic. Although adsorption performance declined after the first reuse cycle, EFBAC demonstrated significant potential as a cost-effective and sustainable adsorbent for leachate treatment. These findings contribute to the circular economy by valorizing agricultural waste and align with the United Nations' Sustainable Development Goals (SDGs) for responsible production and climate action.

Eco-nano solutions for rapid phosphorus recovery: Closing the loop for sustainable agriculture

Efficient phosphorus (P) removal from agricultural drainage is crucial for making its removal and recovery economically viable and operationally feasible. This study evaluated cost-effective, green-synthesized nanoparticles (using grass extract) for rapid and efficient P adsorption. Batch experiments were conducted to assess the effect of pH, P concentration, adsorbent dosage, contact time, and temperature on P adsorption. The nanoparticles removed 20 mg/L of P in 5 min, demonstrating their significant potential for effective adsorption in short retention time. They achieved a maximum adsorption capacity of 77.5 mg g-1, outperforming their chemically synthesized counterparts. Moreover, smaller particles exhibited faster initial adsorption, while larger ones contributed more to overall adsorption over time. Modeling results revealed that rapid initial P adsorption was driven by physisorption, while chemisorption controlled the rate of adsorption in the later stages. After five regeneration cycles, the nanoparticles retained over 50 % of their adsorption capacity, demonstrating strong reusability potential. Further research is needed to optimize these nanoparticles for P removal from dynamic agricultural drainage, offering a cost-effective and sustainable solution for P management.

Synthetic Aggregates and Bituminous Materials Based on Industrial Waste

The transition to a circular economy requires new materials and products with new production designs, technologies, and processes. In order to create new materials with physico-chemical qualities suitable for application in the building materials engineering sector, stone dust and polymer waste-two environmentally hazardous industrial wastes-were combined in this study. The materials obtained were evaluated based on an analysis performed using the Micro-Deval test. The results obtained showed a Micro-Deval coefficient value of 7.7%, indicating that these artificial aggregates can replace the natural aggregates used in road construction. Additionally, it was shown that the stone dust used could be applied as a sorbent for dyes without later leaching this dye from the final synthetic stones. Another category of materials that meets the principles of the circular economy and was developed in this study is bituminous mastic, which is currently used for the hot sealing of joints in road infrastructure. For this purpose, a composite material was developed using stone dust and cooking oil to replace the filler, a non-regenerable source used for obtaining bituminous mixtures. Specific standard methods were used to assess the degree to which the new materials approach the behavior of commercially available products.

Sustainable polymeric adsorbents for adsorption-based water remediation and pathogen deactivation: a review

Water is a fundamental resource, yet various contaminants increasingly threaten its quality, necessitating effective remediation strategies. Sustainable polymeric adsorbents have emerged as promising materials in adsorption-based water remediation technologies, particularly for the removal of contaminants and deactivation of water-borne pathogens. Pathogenetic water contamination, which involves the presence of harmful bacteria, viruses, and other microorganisms, poses a significant threat to public health. This review aims to analyze the unique properties of various polymeric materials, including porous aromatic frameworks, biopolymers, and molecularly imprinted polymers, and their effectiveness in water remediation applications. Key findings reveal that these adsorbents demonstrate high surface areas, tunable surface chemistries, and mechanical stability, which enhance their performance in removing contaminants such as heavy metals, organic pollutants, and emerging contaminants from water sources. Furthermore, the review identifies gaps in current research and suggests future directions, including developing multifunctional polymeric materials and integrating adsorption techniques with advanced remediation technologies. This comprehensive analysis aims to contribute to advancing next-generation water purification technologies, ensuring access to clean and safe water for future generations.

Cellulose Acetate Supported MOF-5/Crystalline Nanocellulose Composite Film as an Adsorbent Material for Methylene Blue Removal from Aqueous Solutions

In this study, a novel, low-cost, and efficient adsorbent film was fabricated by a solvothermal method. The adsorbent film was developed to be hydrolytically stable, not vulnerable to aggregation in aqueous environments, and not prone to secondary contamination. The adsorbent consists of cellulose acetate (CA) as a support embedded with a MOF-5/crystalline nanocellulose (CNC) composite material. The CA-supported MOF-5/CNC film was characterized using a variety of techniques, including X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, which revealed hydroxyl and carbonyl functional groups on the adsorbent film. The film was evaluated for the adsorptive removal of methylene blue (MB) from an aqueous solution. Adsorption was characterized by a rapid increase in MB adsorption during the first hour with equilibrium achieved within 4-5 h into the adsorption process. The maximum adsorption capacity was determined to be 4.29 mg/g and the maximum dye removal efficiency was 77%. The MB adsorption process best fitted the Freundlich isotherm and pseudo-second-order kinetic models. Thermodynamic studies showed that the adsorption was exothermic and feasible. The adsorbent film showed admirable regeneration ability, demonstrating its cost-effectiveness and its potential as a promising material for wastewater treatment.

Inclusive study of peanut shells derived activated carbon as an adsorbent for removal of lead and methylene blue from water

Green and efficient agro-waste-based activated carbon has been prepared utilizing peanut shells for adsorptive elimination of an industrial dye, methylene blue, and lead from polluted water. The carbonaceous biomass obtained from peanut shells was chemically activated using either NaOH, ZnCl2, or steam and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2 adsorption and desorption studies. The adsorption process was optimal for methylene blue at alkaline pH, while pH 4.5 was optimal for Pb (II) adsorption. The adsorption takes place through pseudo-second-order kinetic, and the rate-governing step of the adsorption procedure are intraparticle diffusion and film diffusion. Furthermore, the thermodynamics of the adsorption process has been studied, and the obtained Gibbs free energy (ΔG°) values are negative (- 35.90 to - 43.59 kJ mol-1) indicating the spontaneous adsorption of the investigated pollutants on the prepared activated carbon. As per the correlation coefficient, the obtained results were best fit by the Langmuir isotherm with maximum adsorption capacity of 303.03 mg g-1 for methylene blue and 130.89 mg g-1 for Pb (II). The activated carbon successfully removed methylene blue and Pb (II) with %removal exceeding 95%. The mechanisms of interaction of Pb (II) with the activated carbon is a combination of electrostatic interaction and ion exchange, while methylene blue interacts with the activated carbon via π-π interaction, hydrogen bonds, and electrostatic interaction. Thus, the prepared activated carbon has been employed to decontaminate wastewater and groundwater samples. The developed agro-waste-based activated carbon is a promising, cost-efficient, green, and accessible tool for water remediation.

Optimization use of watermelon rind in the coagulation-flocculation process by Box Behnken design for copper, zinc, and turbidity removal

Watermelon rinds were investigated as a bio-coagulant for treating water contaminated by metals and turbidity, owing to their biodegradability and greater environmental friendliness compared to chemical coagulants. Fourier transform infrared spectroscopy, scanning electron microscopy paired with energy dispersive X-ray analysis and X-ray diffraction characterized the watermelon rinds before and after use. A Box-Behnken experimental design optimized the most influential parameters of initial pH, coagulant dose, and particle size based on response surface methodology. This analysis revealed the experimental data fit quadratic polynomial models, achieving maximum removal efficiencies of 97.51 % for zinc, 99.88 % for copper, and 99.21 % for turbidity under optimal conditions. Statistical analysis confirmed the models effectively captured the experimental data. Analysis of variance denoted the high significance of the quadratic effects of dose and pH. Removal of metal ions Zn2+ and Cu2+ was significantly impacted by these factors. The watermelon rind powder retained its coagulation efficiency after five cycles of reuse, with removal rates of 80.04 % for Zn, 88.33 % for Cu and 86.24 % for turbidity. These results demonstrate the potential of watermelon rind as an alternative coagulant for wastewater treatment. Further testing on real industrial effluents at larger scales would help assess their feasibility for real-world applications.

Facile fabrication of sulfonated porous yeast carbon microspheres through a hydrothermal method and their application for the removal of cationic dye

Water pollution containing dyes become increasingly serious environmental problem with the acceleration of urbanization and industrialization process. Renewable adsorbents for cationic dye wastewater treatment are becoming an obstacle because of the difficulty of desorbing the dye from the adsorbent surface after adsorption. To overcome this dilemma, herein, we report a hydrothermal method to fabricate sulfonic acid modified yeast carbon microspheres (SA/YCM). Different characterization techniques like scanning electron microscopy, FTIR spectroscopy, and X-ray diffraction have been used to test the SA/YCM. Decorated with sulfonic acid group, the modified yeast carbon microspheres possess excellent ability of adsorbing positively charged materials. The removal rate of Methyl blue (MB) by renewable adsorbent SA/YCM can reach 85.3% when the concentration is 500 mg/L. The SA/YCM regenerated by HCl showed excellent regeneration adsorption capacity (78.1%) after five cycles of adsorption-desorption regeneration experiment. Adsorption isotherm and kinetic behaviors of SA/YCM for methylene blue dyes removal were studied and fitted to different existing models. Owing to the numerous sulfonic acid groups on the surface, the SA/YCM showed prominent reusability after regeneration under acidic conditions, which could withstand repeated adsorption-desorption cycles as well as multiple practical applications.

A critical review and bibliometric analysis of methylene blue adsorption using leaves

The rapid development of the industrial world causes wastewater containing dyes to continue to increase. Even in recent years, the food, textile, cosmetic, plastic, and printing industries have developed the use of dyes. Methylene blue (MB) is one of the cationic dyes widely used in dyeing silk, wood, and cotton because of its absorbency and good fastness to materials. The adsorption process is the best technique and preferred in removing dyes from wastewater due to excellent selectivity, high efficiency from high-quality treated effluent, flexibility in design, and simplicity. Therefore, there is a growing interest to identify low-cost alternative adsorbents that have reasonable adsorption efficiency, especially natural materials such as leaves. In this study, research on MB adsorption using leaves was analyzed using bibliometric analysis. Information of bibliometric is extracted from the Scopus database with the keyword "Methylene Blue", "Adsorption or Desorption", and "Leaves or leaf". The results showed that India, Desalination and Water Treatment, and SASTRA Deemed University were the country, journal, and institution that contributed the most publications on this topic. Therefore, it is expected that with the use of bibliometrics, the use of leaf-based MB adsorption processes in their potential for MB dye removal can be investigated especially for large-scale development.

Studies on the Process of Basic Dyes Adsorption on Uniform Spherical Carbons

The influence of carbon pore structure on the sorption process of selected cationic dyes has been investigated. The structure and surface of carbonaceous materials have been characterized basing on various techniques: scanning electron microscopy, low temperature nitrogen adsorption-desorption measurements, X-ray photoelectron spectroscopy and thermal analysis combined with identification of gaseous products. The kinetic and equilibrium adsorption measurements of Basic Violet 3, Basic Red 1 and Basic Blue 9 from aqueous media were performed. The studied carbons seem to be promising adsorbents towards dyes, taking into account the easy-to-use uniform spherical form of the granules and a complex type of porosity with micro-, meso- and macropores appropriate for large molecule adsorption.

Sustainable aerogels based on biobased poly (itaconic acid) for adsorption of cationic dyes

This work reports the synthesis of poly (itaconic acid) by thermal polymerization mediated by 2,2'-Azobis(2-methylpropionamidine) dihydrochloride. Furthermore, physical hydrogels were prepared by using high molecular weight poly (itaconic acid) characterized by low dispersity and laponite RD. The hydrogels presented porous 3D network structures, with a high-water penetration of almost 2000 g/g of swelling ratio, which can allow the adsorption sites of both poly (itaconic acid) and laponite RD to be easily exposed and facilitate the adsorption of dyes. The water adsorption followed Schott's pseudo-second-order model. The mechanism of the adsorption process was investigated using 1H and 31P NMR. The hydrogel is able to fast adsorb by a combination of electrostatic interactions and hydrogen bonding by the synergic effect of the clay and poly (itaconic acid). Moreover, the prepared aerogels exhibited a fast removal of Basic Fuchsin, with an adsorption capacity of 67.56 mg/g and a high removal efficiency (~99 %). The adsorption followed the pseudo-second-order kinetic model and Langmuir isotherm model. Furthermore, the thermodynamic parameters showed that the BF process of adsorption was spontaneous and feasible, endothermic, and followed physisorption. These results indicated that the PIA/laponite-based aerogel can be considered a promising adsorbent material in textile wastewater treatment.

Synthesis and Properties of Cobalt/Nickel-Iron-Antimony(III, V)-Oxo Tartrate Cluster-Based Compounds

Two types of isostructural iron-cobalt/nickel-antimony-oxo tartrate cluster-based compounds, namely (H3O)(Me2NH2)[M(H2O)6]2[FeII2SbIII12(μ4-O)3(μ3-O)8(tta)6]·6H2O (M = Co (1); Ni (3)), H5/3[Co2.5FeII4/3FeIII3(H2O)13SbV1/3FeIII2/3(μ4-O)2(μ3-O)4SbIII6(μ3-O)2(tta)6]·2H2O (2) and H2[Ni2.25FeII1.5FeIII3(H2O)14SbV0.25FeIII0.75(μ4-O)2(μ3-O)4SbIII6(μ3-O)2(tta)6]·2H2O (4) (H4tta = tartaric acid) were synthesized via simple solvothermal reactions. All the clusters in the structures adopt sandwich configurations, that is, bilayer sandwich configuration in 1 and 3 and monolayer sandwich configuration in 2 and 4. Interestingly, the monolayer sandwiched compounds 2 and 4 represent rare examples of cluster-based compounds containing mixed-valence Sb(III, V), whose center of the intermediate layer is the co-occupied [FexSbV1-x]. This is different from that of previously reported sandwich-type antimony-oxo clusters in which the center position is either occupied by a transition metal ion or a Sb(V) alone. Thus, the discovery of title compounds 2 and 4 makes the evolution of center metal ion more complete, that is, from M, MxSbV1-x to SbV. All the title compounds were fully characterized, and the photocatalysis, proton conduction and magnetism of compounds 2 and 4 were studied.

Surface activity, mechanisms, kinetics, and thermodynamic study of adsorption of malachite green dye onto sulfuric acid-functionalized Moringa oleifera leaves from aqueous solution

In the present study, activated carbon prepared from H2SO4-functionalized Moringa oleifera leaves (ACMOL) was used as a potential adsorbent for the effective removal of malachite green (MG) dye from aqueous media. FT-IR, SEM, EDS, Zeta potential, XRD, BET, proximate, and CHNS analysis techniques were used for surface characterization of the ACMOL. The adsorption efficiency of the ACMOL was investigated as a function of varying adsorbent dosage (0.02-0.2 g/100 mL), pH (3.0-9.0), ionic strength (0.1-0.5 M KCl), urea concentration (0.1-0.5 M), contact time (30-210 min), and temperature (303-323 K). The representative adsorption isotherms belong to the typical L-type. Maximum percentage removal was found to be 84% (124.40 mg/g) for MG dye concentration (30 mg/L) at pH 7.0 and 303 K with ACMOL dose 0.02 g/100 mL. The adsorption kinetics and equilibrium experimental data of MG dye adsorption on the ACMOL were well explained by the pseudo-second-order kinetics (R2 = 0.99) and Langmuir isotherm model (R2 = 0.99), respectively. The value of adsorption and desorption coefficient was found to be 0.036 min-1 and 0.025 mg min-1/L, respectively. Thermodynamic study showed the spontaneous (ΔG° =  - 31.33, - 31.92, and - 32.49 kJ/mol at temperatures 303 K, 313 K, and 323 K, respectively) and exothermic (ΔH° =  - 13.7 kJ/mol) nature of the adsorption with some structural changes occurring on the ACMOL surface (ΔS° = 58.198 J/K·mol).

Turning waste avocado stones and montmorillonite into magnetite-supported nanocomposites for the depollution of methylene blue: adsorbent reusability and performance optimization

The existence of methylene blue (MB) in wastewater even as traces is raising environmental concerns. In this regard, the performances of four adsorbents, avocado stone biochar (AVS-BC), montmorillonite (MMT), and their magnetite Fe3O4-derived counterparts, were compared. Results showed the superior performance of Fe3O4@AVS-BC and Fe3O4@MMT nanocomposites with removal percentages (%R) of 95.59% and 88%. The morphological features of AVS-BC as revealed by SEM analysis showed a highly porous surface compared to a plane and smooth surface in the case of MMT. Surface analysis using FT-IR and Raman spectroscopies corroborated the existence of the Fe-O peaks upon loading with magnetite. The XRD analysis confirmed the formation of cubic magnetite nanoparticles. The adsorption process in the batch mode was optimized using central composite design (CCD). Equilibrium and kinetic isotherms showed that the adsorption of MB onto Fe3O4@AVS-BC fitted well with the Langmuir isotherm and the pseudo-second-order (PSO) model. The maximum adsorption capacity (qm) was 118.9 mg/g (Fe3O4@AVS-BC) and 72.39 mg/g (Fe3O4@MMT). The Fe3O4@AVS-BC showed a higher selectivity toward MB compared to other organic contaminants. The MB-laden adsorbent was successfully used for the remediation of Cr (III), Ni (II), and Cd (II) with removal efficiencies hitting 100% following thermal activation.

Adsorptive removal of acid red 18 dye from aqueous solution using hexadecyl-trimethyl ammonium chloride modified nano-pumice

Discharging untreated dye-containing wastewater gives rise to environmental pollution. The present study investigated the removal efficiency and adsorption mechanism of Acid Red 18 (AR18) utilizing hexadecyl-trimethyl ammonium chloride (HDTMA.Cl) modified Nano-pumice (HMNP), which is a novel adsorbent for AR18 removal. The HDTMA.Cl is characterized by XRD, XRF, FESEM, TEM, BET and FTIR analysis. pH, contact time, initial concentration of dye and adsorbent dose were the four different parameters for investigating their effects on the adsorption process. Response surface methodology-central composite design was used to model and improve the study to reduce expenses and the number of experiments. According to the findings, at the ideal conditions (pH = 4.5, sorbent dosage = 2.375 g/l, AR18 concentration = 25 mg/l, and contact time = 70 min), the maximum removal effectiveness was 99%. The Langmuir (R2 = 0.996) and pseudo-second-order (R2 = 0.999) models were obeyed by the adsorption isotherm and kinetic, respectively. The nature of HMNP was discovered to be spontaneous, and thermodynamic investigations revealed that the AR18 adsorption process is endothermic. By tracking the adsorption capacity of the adsorbent for five cycles under ideal conditions, the reusability of HMNP was examined, which showed a reduction in HMNP's adsorption effectiveness from 99 to 85% after five consecutive recycles.

Hungarian and Indonesian rice husk as bioadsorbents for binary biosorption of cationic dyes from aqueous solutions: A factorial design analysis

The wastewater of the dye industry can be characterized by a complex chemical composition and consists of numerous dyes. Bioadsorbents are increasingly applied for the biosorption of dyes because they are inexpensive and environmentally friendly. Rice husk (RH) is a potential agricultural waste that can be converted into a bioadsorbents for the biosorption of cationic dyes. Herein, the removal of methylene blue (MB) and basic red 9 (BR9) dyes by Hungarian rice husk (HRH) and Indonesian rice husk (IRH) using binary biosorption was investigated. Adsorbents were characterized by zeta potential, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Batch biosorption evaluated the influence of different variables, including pH, adsorbent dose, contact time, and initial concentrations. Several factors that influence the biosorption of MB and BR9 onto rice husk were assessed using main effect, Pareto charts, normal probability plots, and interaction effect in a factorial design. The optimum contact time was 60 min. Isotherm and kinetic models of MB and BR9 in binary biosorption fitted to the Brunauer-Emmett-Teller multilayer and the Elovich equation based on correlation coefficients and nonlinear chi-square. Results showed that the biosorption capacity of HRH was 10.4 mg/g for MB and 10 mg/g for BR9; values for IRH were 9.3 mg/g and 9.6 mg/g, respectively. Therefore, HRH and IRH were found to be effective adsorbents for removing MB and BR9 via binary biosorption.

Preparation of Fe/Ni-MOFs for the Adsorption of Ciprofloxacin from Wastewater

This work studies the use of Fe/Ni-MOFs for the removal of ciprofloxacin (CIP) in wastewater. Fe/Ni-MOFs are prepared by the solvothermal method and characterized by X-ray diffraction (XRD), a scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and a thermal gravimetric analyzer (TG). Under the conditions of the concentration of 50 ppm, a mass of 30 mg, and a temperature of 30 °C, the maximum adsorption capacity of ciprofloxacin removal within 5 h was 232.1 mg/g. The maximum removal rate was 94.8% when 40 mg of the Fe/Ni-MOFs was added to the solution of 10 ppm ciprofloxacin. According to the pseudo-second-order (PSO) kinetic model, the R² values were all greater than 0.99, which proved that the adsorption theory of ciprofloxacin by Fe/Ni-MOFs was consistent with the practice. The adsorption results were mainly affected by solution pH and static electricity, as well as other factors. The Freundlich isotherm model characterized the adsorption of ciprofloxacin by Fe/Ni-MOFs as multilayer adsorption. The above results indicated that Fe/Ni-MOFs were effective in the practical application of ciprofloxacin removal.

Removal of cadmium and lead ions from aqueous solutions by novel dolomite-quartz@Fe3O4 nanocomposite fabricated as nanoadsorbent

The elimination of heavy metal ion contaminants from residual waters is critical to protect humans and the environment. The natural clay (dolomite and quartz) based composite Fe₃O₄ nanoparticles (DQ@Fe₃O₄) has been largely explored for this purpose. Experimental variables such as temperature, pH, heavy metal concentration, DQ@Fe₃O₄ dose, and contact time were optimized in details. The DQ@Fe₃O₄ nanocomposite was found to achieve maximum removals of 95.02% for Pb²⁺ and 86.89% for Cd²⁺, at optimal conditions: pH = 8.5, adsorbent dose = 2.8 g L^-1, the temperature = 25 °C, and contact time = 140 min, for 150 mg L^-1 heavy metal ion initial concentration. The Co-precipitation of dolomite-quartz by Fe₃O₄ nanoparticles was evidenced by SEM-EDS, TEM, AFM, FTIR, XRD, and TGA analyses. Further, the comparison to the theoretical predictions, of the adsorption kinetics, and at the equilibrium, of the composite, revealed that they fit, respectively to, the pseudo-second-order kinetic, and Langmuir isotherm. These both models were found to better describe the metal binding onto the DQ@Fe₃O₄ surface. This suggested a homogenous monolayer sorption dominated by surface complexation. Additionally, thermodynamic data have shown that the adsorption of heavy metal ions is considered a spontaneous and exothermic process. Moreover, Monte Carlo (MC) simulations were performed in order to elucidate the interactions occurring between the heavy metal ions and the DQ@Fe₃O₄ nanocomposite surface. A good correlation was found between the simulated and the experimental data. Moreover, based on the negative values of the adsorption energy (Eads), the adsorption process was confirmed to be spontaneous. In summary, the as-prepared DQ@Fe₃O₄ can be considered a low-cost-effective heavy metals adsorbent, and it has a great potential application for wastewater treatment.

Zero-Waste Approach for Heavy Metals' Removal from Water with an Enhanced Multi-Stage Hybrid Treatment System

The aim of the work was to develop a zero-waste technological solution for hybrid removal of heavy metals from river sediments. The proposed technological process consists of sample preparation, sediment washing (a physicochemical process for sediment purification), and purification of the wastewater produced as a by-product. A suitable solvent for heavy metal washing and the effectiveness of heavy metal removal were determined by testing EDTA and citric acid. The process for removing heavy metals from the samples worked best with citric acid when the 2% sample suspension was washed over a 5-h period. The method was chosen of the adsorption of heavy metals from the exhausting washing solution on natural clay. Analyses were performed of the three main heavy metals, Cu(II), Cr(VI), and Ni(II), in the washing solution. Based on the laboratory experiments, a technological plan was prepared for the purification of 100,000 tons of material per year.