Functionalized layered double hydroxides composite bio-adsorbent for efficient copper(II) ion encapsulation from wastewater

Cesium removal from contaminated montmorillonite using ethylene glycol monoethyl ether and Freezing-Thawing process

The unexpected nuclear accidents and uncontrolled leakages of radioactive cesium (137Cs) can contaminate the soils nearby nuclear power plants (NPPs). Radioactive 137Cs ions (Cs+) tend to strongly sorb on 2:1 phyllosilicate clay minerals, especially expandable clay minerals such as montmorillonite (MMT) and vermiculite. However, removal of 137Cs from the contaminated soils has been relatively inefficient due to the strong and irreversible interaction of Cs with the frayed edge sites in clays. This study employs the intercalation of ethylene glycol monoethyl ether (EGME) and the Freezing-Thawing (FT) approach to enhance the removal rate of cesium (Cs+) from Cs-contaminated montmorillonite (CsMMT) by the enhanced K+ ion exchange process. The EGME intercalated into the interlayer of the CsMMT and induced the interlayer expansion. The interlayer spacing of the CsMMT was expanded from 19.09 Å to 22.01 Å when 3.8 mmol EGME/g MMT was treated. For ion exchange with 4 mmol/g CsMMT of K+ without EGME intercalation, the Cs removal rate was observed to only 34.71 %, which was enhanced to 59.34 % after 3.8 mmol EGME/g CsMMT of treatment. In addition, the FT process further increased Cs removal up to 82.31 % by inducing the expansion of the interlayer and exfoliating the MMT. We believe that CsMMT can be efficiently decontaminated by applying both the intercalation of EGME and FT approach together.

Levofloxacin Synergistic Capture Using a "Memory-Effect" Layered Double Oxides Loaded with ZIF-67 Nanoparticles

Layered double hydroxides (LDHs) are limited by a lack of adsorption active sites and low porosity, leading to a suboptimal performance in antibiotic adsorption. In this study, LDH was used as templates to obtain LDO through high-temperature calcination, creating rapid mass transfer channels for LVX, thereby enhancing adsorption capacity and reducing adsorption time. Subsequently, small ZIF-67 crystals were grown in situ between the layers and on the surface of LDOs, providing additional adsorption active sites and surface area to the LDO@ZIF-67 composite material. In the LVX removal process, the synergistic effect between LDO and ZIF-67 mainly depends on the "memory effect" and the interaction of various mechanisms such as metal complexation, hydrogen bonding, and electrostatic attraction. LDO@ZIF-67 exhibits a rapid adsorption rate toward LVX, reaching adsorption equilibrium within 40 min, with an adsorption capacity as high as 268 mg/g, surpassing values reported in some literature. The adsorption process was more consistent with the Langmuir (R2 = 0.992) and pseudo-second-order kinetic model (R2 = 0.991). The analysis of adsorption thermodynamics results showed that the adsorption capacity gradually decreased with the increase of temperature, which belonged to the adsorption process of spontaneous exothermicity and reduced degree of freedom. In addition, LDO@ZIF-67 still maintains a good porous crystal structure after 5 cycles of adsorption-desorption, and the adsorption capacity can reach 214 mg/g. This study highlights the significant potential of LDO@ZIF-67 for removal of LVX from aqueous solutions and its promising application in wastewater treatment.

Environmental sustainable ZrO2 -phosphorous Biochar nano composite derived from sugarcane bagasse and their adsorption behavior of antidepressant drugs

Phosphorous biochar was synthesized from sugarcane bagasse (SB) by applying a 2:1 weight ratio of H3PO4 to OP and pyrolyzing it at 600 °C under nitrogen. Sugarcane bagasse was selected for its affordability and environmental benefits as a carbon support. Following this, a zirconium-loaded PC nanocomposite (ZrP400) was developed by impregnating zirconium hydroxide in concentrations 5-30% onto the mesoporous phosphorous biochar, which was then thermally treated at 400ºC. Analytical techniques showed that the ZrP400 adsorbents had a high surface area (1697-2434 m²/g) and considerable porosity. The effectiveness of these adsorbents in removing the hazardous tricyclic antidepressant amitriptyline (AMT) from water was tested. At a pH of 6.52, the neutral adsorbent provided various chemical functional groups that facilitated the binding of amitriptyline. With 20 mg of adsorbent at 35ºC, the capacity for amitriptyline adsorption reached up to 585 mg/g. Adsorption equilibrium was reached within 120 min over a concentration range of 10 to 300 mg/L. Kinetic and equilibrium data showed that the adsorption was well described by the pseudo-second-order and Freundlich isotherm models, indicating that chemisorption was the primary mechanism, with physisorption also contributing significantly to amitriptyline removal. The spent adsorbent could be effectively regenerated using ethanol. Additionally, the process's sustainability was assessed using GAPI and AGREE metrics, which confirmed its environmental friendliness, practicality, and sustainability.

Green Fabrication of Zinc-Based Metal-Organic Frameworks@Bacterial Cellulose Aerogels via In Situ Mineralization for Wastewater Treatment

Compared to conventional adsorbents, zinc-based metal-organic frameworks (MOFs) such as zeolite imidazolium skeleton-8 (ZIF-8) exhibit enhanced thermal, chemical, and structural stability. Nonetheless, their powdered form results in limited dispersibility in aqueous solutions and a tendency to aggregate, which significantly restricts their utility in adsorption applications. This study reports a green composite aerogel through the in situ mineralization of ZIF-8 onto bacterial cellulose (BC) for the effective removal of toxic metal ions (Cu2+) and Congo red (CR) from wastewater. The ZIF@BC composite aerogel was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and specific surface area analysis. The findings indicated that the ZIF-8 produced were evenly distributed across the BC nanonetwork, facilitating effective adsorption of CR and Cu2+. The maximum adsorption capacities of the ZIF@BC aerogels were determined to be 397.55 mg/g for CR and 424.80 mg/g for Cu2+, as per the Langmuir isotherm. Furthermore, the ZIF-8@BC aerogels demonstrated excellent selectivity and reusability, particularly for CR adsorption. The proposed mechanism for the interaction between the composite aerogel and CR and Cu2+ involves electrostatic interactions, hydrogen bonding, π-π bonding, coordination bonding, ion exchange, microchemical precipitation, and pore diffusion. This research offers significant promise for the utilization of MOF powders and highlights substantial industrial potential.

Effective removal of Cu (II) ions from aqueous solutions using low-cost, eco-friendly natural and modified potato peels

In this study, the researchers wanted to find out if potato peels (PP) and modified potato peels (MPP) could be used to remove Cu (II) ions from water solutions. The effect of adsorption parameters such as pH, contact time, adsorbent dose, and initial concentration were systematically optimized, and the adsorption kinetics and isotherms were investigated for potential use in real sample operations. The physicochemical properties and morphological structure of the adsorbent were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy to understand the Cu (II) ion adsorption mechanism. The studies carried out at different temperatures provided a deeper understanding of the adsorption capacities of the adsorbents. The Cu (II) ion removal capacities of PP were determined as 30.95, 32.67, and 35.33 mg/g at 25, 35, and 45 °C, respectively. Under the same conditions, the removal capacities of MPP were found to be 76.33, 80.64, and 86.20 mg/g, respectively. Further investigation of the adsorption kinetics showed that the experimental data fit the pseudo-second-order model for both PP and MPP adsorbents. Thermodynamic analyses revealed that the adsorption of Cu(II) ions onto the adsorbents was an endothermic process and spontaneous. PP and MPP could be reused for several cycles without losing their adsorption performance after successful regeneration with 0.10 M HCl. The mechanism of Cu (II) ion removal was explained by intermediary ion exchange, surface precipitation, and interaction between surface functionalities of PP and MPP. Therefore, highly functional PP and MPP could be promising adsorbents for efficient Cu (II) ion removal from aqueous solutions.

Valorization of carbon soot ash for the selective capture of lead ions from industrial waste water-A waste to resource approach

Landfills are struggling to accommodate the increasing amounts of carbon soot ash waste from oil refineries. Due to extensive industrial productions, large quantities of lead ions are released into the environment, which not only pollutes the environment but also affects flora and fauna. In this work, these urgent environmental issues will be tackled by studying the use of modified carbon soot ash for specific heavy metal adsorption. Carbon soot ash modified with chemical leaching and physical ball-milling was loaded onto the surface of graphene oxide. This adsorbent was found to selectively adsorb and remove toxic lead ions (>99%) from a mixed heavy metal solution. The adsorption efficiency was found to increase with temperature (20-60 °C) and pH (2-8). Langmuir isotherm and pseudo-second order kinetics were found to fit the adsorption process through curve fitting, where the adsorbent reached a maximum capacity of 194.55 mg/g. Potential mechanisms for lead adsorption and metal specificity are also discussed here. This work aligns with the waste-to-resource pathway, where waste carbon soot ash is diverted from landfilling and is formulated as a specific heavy metal adsorbent, that shows promise for environmental remediation.

Effect of environmental factors on adsorption of ciprofloxacin from wastewater by microwave alkali modified fly ash

Antibiotics, as emerging persistent pollutants, pose significant threats to human health. The effective and low-cost removal of ciprofloxacin (CIP) from wastewater has become an important research focus. In this study, fly ash (FA) was used as the raw material, and modified fly ash (MFA) was prepared by varying microwave power, alkali concentration, and immersion time to investigate its adsorption characteristics for CIP. Results showed that the optimal preparation conditions for MFA with the most effective adsorption of CIP, using the Box-Behnken response surface methodology, were a microwave power of 480 W, an alkali concentration of 1.5 mol/L, and a modification time of 3 h. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses revealed that after modification, the glassy structure of FA is destroyed, the specific surface area is increased, and obvious hydroxyl O-H absorption peaks appear. Both FA and MFA exhibited adsorption processes for CIP that conformed to pseudo-second-order kinetics and the Langmuir equation. Maximum adsorption of CIP (9.61 and 12.67 mg/g) was achieved at pH = 6. With increasing temperature, the adsorption capacity of both FA and MFA for CIP decreased, indicating an exothermic process. The adsorption capacity of CIP decreased with increasing ion concentration, with the impact order of ions being Al3+  > Ca2+  > Na+. The results show that pore filling, electrostatic interaction, ion exchange and complexation are the main ways of CIP adsorption by FA. Microwave alkali modified fly ash is an economical and efficient adsorbent for CIP removal in water, realizing the purpose of "treating waste with waste". This study provides a scientific basis for controlling CIP treatment in wastewater.

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.

Progress in layered double hydroxides (LDHs): Synthesis and application in adsorption, catalysis and photoreduction

Layered double hydroxides (LDHs), also known as anionic clays, have attracted significant attention in energy and environmental applications due to their exceptional physicochemical properties. These materials possess a unique structure with surface hydroxyl groups, tunable properties, and high stability, making them highly desirable. In this review, the synthesis and functionalization of LDHs have been explored including co-precipitation and hydrothermal methods. Furthermore, extensive research on LDH application in toxic pollutant removal has shown that modifying or functionalizing LDHs using materials such as activated carbon, polymers, and inorganics is crucial for achieving efficient pollutant adsorption, improved cyclic performance, as well as effective catalytic oxidation of organics and photoreduction. This study offers a comprehensive overview of the progress made in the field of LDHs and LDH-based composites for water and wastewater treatment. It critically discusses and explains both direct and indirect synthesis and modification techniques, highlighting their advantages and disadvantages. Additionally, this review critically discusses and explains the potential of LDH-based composites as absorbents. Importantly, it focuses on the capability of LDH and LDH-based composites in heterogeneous catalysis, including the Fenton reaction, Fenton-like reactions, photocatalysis, and photoreduction, for the removal of organic dyes, organic micropollutants, and heavy metals. The mechanisms involved in pollutant removal, such as adsorption, electrostatic interaction, complexation, and degradation, are thoroughly explained. Finally, this study outlines future research directions in the field.

Graphene oxide@Fe3O4-decorated iota-carrageenan composite for ultra-fast and highly efficient adsorption of lead (II) from water

The aggravated problem of lead pollution, especially in aquatic environments, necessitates the development of eminent adsorbents that could radically solve this environmental problem. Hence, a new composite was constructed based on iota carrageenan (i.Carr), graphene oxide (GO) and magnetite (Fe3O4) for removing noxious Pb2+ ions. The GO@Fe3O4-i.Carr composite was characterized by VSM, SEM, XPS, XRD, FTIR and Zeta potential. The removal of Pb2+ ions attained a quick equilibrium of almost 30 min with a removal efficiency reaching 93.68 %. The removal of Pb2+ was boosted significantly, in the order of GO@Fe3O4-i.Carr(1:1) > GO@Fe3O4-i.Carr(1:3) > GO@Fe3O4-i.Carr(3:1). Moreover, acquired experimental data fitted the pseudo 2nd order kinetic model and Freundlich isotherm model with a maximal monolayer adsorption capacity reached 440.05 mg/g. Notably, after five adsorption runs, the composite maintained its removal efficiency exceeding 74 %. The assumed adsorption mechanisms of Pb2+ onto GO@Fe3O4-i.Carr were complexation, precipitation, Lewis acid-base, and electrostatic attraction forces. Overall, the GO@Fe3O4-i.Carr composite elucidated the auspicious adsorbent criteria, comprising fast adsorption with high performance, ease-separation and tolerable recyclability, advising its feasible use to decontaminate water bodies from hazardous heavy metals.

KOH-modified bamboo charcoal loaded with α-FeOOH for efficient adsorption of copper and fluoride ions from aqueous solution

In this work, bamboo charcoal (BC) is prepared by pyrolysis of bamboo. Then, KOH modification and surface deposition of Goethite (α-FeOOH) are performed to obtain a new KOH-modified BC loaded with α-FeOOH (FKBC) adsorbent for copper (Cu2+) and fluoride (F-) ion adsorption from aqueous solution. Surface morphology and physiochemical properties of the prepared adsorbent are characterized by scanning electron microscopy-energy dispersive spectrometer, X-ray diffraction, and N2 adsorption-desorption. The effect of pH, contact time, adsorbent dosage, and initial concentration on Cu2+ and F- adsorption is also investigated. In addition, adsorption kinetics and isotherms are fitted to pseudo-second-order kinetics and Langmuir model, respectively. Thermodynamic parameters suggest that the adsorption process is spontaneous and endothermic. The adsorption mechanism is further characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The Cu2+ absorption mainly occurs through ion exchange, coordination reactions, and surface precipitation, while the F- adsorption mainly occurs via ion exchange and hydrogen bonding. The selective adsorption experiments reveal that FKBC has good selectivity for Cu2+ and F-. The adsorption-desorption experimental results indicate that FKBC can be reused for Cu2+ and F- adsorption after regeneration. Results indicate that FKBC can be a promising adsorbent for Cu2+ and F- removal from aqueous solutions.

Recovery of platinum group metal resources from high-level radioactive liquid wastes by non-contact photoreduction

Recovery of platinum group metals (PGMs) including palladium (Pd), rhodium (Rh), and ruthenium (Ru) from high-level radioactive liquid waste (HLLW) possesses enormous environmental and economic benefits. A non-contact photoreduction method was herein developed to selectively recover each PGM from HLLW. Soluble Pd(II), Rh(III), and Ru(III) ions were reduced to insoluble zero-valent metals and separated from simulated HLLW containing neodymium (Nd) as a representative for lanthanides, another main component in HLLW. Detailed investigation on the photoreduction of different PGMs revealed that Pd(II) could be reduced under 254- or 300-nm UV exposure using either ethanol or isopropanol as reductants. Only 300-nm UV light enabled the reduction of Rh(III) in the presence of ethanol or isopropanol. Ru(III) was the most difficult to reduce, which was only realized by 300-nm UV illumination in isopropanol solution. The effects of pH was also studied, suggesting that lower pH favored the separation of Rh(III) but hindered the reduction of Pd(II) and Ru(III). A delicate three-step process was accordingly designed to achieve the selective recovery of each PGM from simulated HLLW. Pd(II) was reduced by 254-nm UV light with the help of ethanol in the first step. Then Rh(III) was reduced by 300-UV light in the second step after the pH was adjusted to 0.5 to suppress the Ru(III) reduction. In the third step, Ru(III) was reduced by 300-nm UV light after isopropanol was added and the pH was adjusted to 3.2. The separation ratios of Pd, Rh, and Ru exceeded 99.8%, 99.9%, and 90.0%, respectively. Meanwhile, all Nd(III) still remained in the simulated HLLW. The separation coefficients between Pd/Rh and Rh/Ru exceeded 56,000 and 75,000, respectively. This work may provide an alternative method to recover PGMs from HLLW, which minimize the secondary radioactive wastes compared with other approaches.

Development of a green metallochromic indicator for selective and visual detection of copper(II) ions

Heavy metal ions, i.e., copper(II) (Cu(II)), are harmful to the environment and our health. The current research established an eco-friendly and efficient metal-sensitive indicator, which can identify Cu(II) ions in both liquid and solid forms, by utilizing anthocyanin extract obtained from jambolao fruit (Syzgium cumini) that is incorporated within bacterial cellulose nanofibers (BCNF).The CIE Lab color parameters demonstrated that Cu(II) binding causes a sensible change in color. It was observed that the visible color altered with an increase in the Cu(II) concentration. The bacterial cellulose nanofibers that were altered with anthocyanin were analyzed using ATR-FTIR and FESEM. The sensor's selectivity was tested by using a range of metal ions such as lead (Pb2+), cobalt (Co2+), cadmium (Cd2+), nickel (Ni2+), aluminium (Al3+), barium (Ba2+), manganese (Mn2+), zinc (Zn2+), mercury (Hg2+) and sodium (Na+). The findings demonstrated that the suggested sensor showed excellent selectivity toward Cu(II) ion. Cu(II) can be accurately identified using the sensing technique, with detection limits ranging from 10-400 ppm and 50-500 ppm for liquid and solid samples, respectively, and through observation with naked eye. The fabricated green metallochromic sensor is promising to be a simple, cheap, mobile and easily operable for the real-time and on-site detection of Cu(II) ion.

Sustainable fabrication of hybrid silver-copper nanocomposites (Ag-CuO NCs) using Ocimum americanum L. as an effective regime against antibacterial, anticancer, photocatalytic dye degradation and microalgae toxicity

In this study, a sustainable fabrication of hybrid silver-copper oxide nanocomposites (Ag-CuO NCs) was accomplished utilizing Ocimum americanum L. by one pot green chemistry method. The multifarious biological and environmental applications of the green fabricated Ag-CuO NCs were evaluated through their antibacterial, anticancer, dye degradation, and microalgae growth inhibition activities. The morphological features of the surface functionalized hybrid Ag-CuO NCs were confirmed by FE-SEM and HR-TEM techniques. The surface plasmon resonance λ_max peak appeared at 441.56 nm. The average hydrodynamic size distribution of synthesized nanocomposite was 69.80 nm. Zeta potential analysis of Ag-CuO NCs confirmed its remarkable stability at -21.5 mV. XRD and XPS techniques validated the crystalline structure and electron binding affinity of NCs, respectively. The Ag-CuO NCs demonstrated excellent inhibitory activity against Vibrio cholerae (19.93 ± 0.29 mm) at 100 μg/mL. Anticancer efficacy of Ag-CuO NCs was investigated against the A549 lung cancer cell line, and Ag-CuO NCs exhibited outstanding antiproliferative activity with a low IC₅₀ of 2.8 ± 0.05 μg/mL. Furthermore, staining and comet assays substantiated that the Ag-CuO NCs hindered the progression of the A549 cells and induced apoptosis as a result of cell cycle arrest at the G₀/G₁ phase. Concerning the environmental applications, the Ag-CuO NCs displayed efficient photocatalytic activity against eosin yellow degradation up to 80.94% under sunlight irradiation. Microalgae can be used as an early bio-indicator/prediction of environmental contaminants and toxic substances. The treatment of the Ag-CuO NCs on the growth of marine microalgae Tetraselmis suecica demonstrated the dose and time-dependent growth reduction and variations in the chlorophyll content. Therefore, the efficient multifunctional properties of hybrid Ag-CuO NCs could be exploited as a regime against infective diseases and cancer. Further, the findings of our investigation witness the remarkable scope and potency of Ag-CuO NCs for environmental applications.

Preparation of novel Zn-Al layered double hydroxide composite as adsorbent for removal of organophosphorus insecticides from water

In this work, a new and efficient composite LDH with high adsorption power using layered double hydroxide (LDH), 2,4-toluene diisocyanate (TDI), and tris (hydroxymethyl) aminomethane (THAM) was designed and prepared, which was used as an adsorbent to adsorb diazinon from contaminated water. The chemical composition and morphology of the adsorbent were evaluated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Energy dispersive X-ray (EDX) and Field emission scanning electron microscopy (FESEM) techniques. Also, the optimal conditions for adsorption of diazinon from water were determined by LDH@TDI@THAM composite. Various parameters like the effect of adsorbent dosage, pH, concentration and contact time of diazinon were studied to determine the optimal adsorption conditions. Then, different isotherm models and kinetic adsorption were used to describe the equilibrium data and kinetic. Also, the maximum adsorption capacity is obtained when the pH of the solution is 7. The maximum adsorption capacity for LDH@TDI@THAM composite was 1000 mg/g at 65 °C and the negative values of ΔG indicate that the adsorption process is spontaneous. After that, studying the reusability of LDH@TDI@THAM composite showed that the removal of diazinon by LDH@TDI@THAM was possible for up to four periods without a significant decrease in performance.

Anthocyanin-induced color changes in bacterial cellulose nanofibers for the accurate and selective detection of Cu(II) in water samples

The environment and our health are negatively impacted by heavy metal ions, like Cu(II). The present study developed a green and effective metallochromic sensor that detects copper (Cu(II)) ions in solution and solid state using anthocyanin extract from black eggplant peels embedded in bacterial cellulose nanofibers (BCNF). Cu(II) is quantitatively detected by the sensing method with detection limits between 10-400 ppm and 20-300 ppm in solution and solid state, respectively. In the solution state, we depicted a sensor for Cu(II) ions in aqueous matrices in the pH range from 3.0 to 11.0, with the capability to produce a visual color change from brown to light blue and dark blue depending on the Cu(II) concentration. Additionally, BCNF-ANT film can act as a sensor for Cu(II) ions in the pH range of 4.0-8.0. Neutral pH was selected from the standpoint of high selectivity. It was found that visible color changed when Cu(II) concentration was increased. Bacterial cellulose nanofibers modified with anthocyanin were characterized with ATR-FTIR and FESEM. Various metal ions, including Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺, Al³⁺, Ba²⁺, Hg²⁺, Mg²⁺, and Na⁺, were used to challenge the sensor to determine its selectivity. Anthocyanin solution and BCNF-ANT sheet were employed in the actual tap water sample successfully. The results also clarified that the various foreign ions did not significantly interfere with Cu(II) ions detection at optimum conditions. Compared to previously developed sensors, no electronic components, trained personnel, or sophisticated equipment were needed to apply the colorimetric sensor developed in this research. Cu(II) contamination in food matrices and water can be monitored on-site easily.

Synthesis of nanostructured novel ion-imprinted polymer for selective removal of Cu2+ and Sr2+ ions from reverse osmosis concentrated brine

This study aims to prepare an ion-imprinted polymer (IIP) using copper sulfate as a template and potassium persulfate as an initiator to selectively adsorb copper ions (Cu²⁺) from aqueous solutions and in an attempt to also test its applicability for removing strontium ions (Sr²⁺). The prepared polymer was denoted by IIP-Cu. Various physical and chemical characterizations were performed for the prepared IIP-Cu. The scanning electron microscopy and transmission electron microscopy analyses confirmed the cavities formed after the removal of the template. It also indicated that the IIP-Cu had a rough and porous topology. The X-ray photoelectron spectroscopy confirmed the successful removal of the Cu template from IIP-Cu. The Brunauer-Emmet-Teller revealed that the surface area of IIP-Cu is as high as 152.3 m²/g while the pore radius is 8.51 nm. The effect of pH indicated that the maximum adsorption of Cu²⁺ was achieved at pH 8 with 98.7%. Isotherm studies revealed that the adsorption of Cu²⁺ was best explained using Langmuir models with a maximum adsorption capacity of 159 mg/g. The effect of temperature revealed that an increase in temperature had an adverse impact on Cu²⁺ removal from the aqueous solution, which was further confirmed by thermodynamic studies. The negative value of standard enthalpy change (-4.641 kJ/mol) revealed that the adsorption of Cu²⁺ onto IIP-Cu was exothermic. While the continuous increase in Gibbs free energy from -6776 kJ/mol to -8385 kJ/mol with the increase in temperature indicated that the adsorption process was spontaneous and feasible. Lastly, the positive value of the standard entropy change (0.023 J/mol.K) suggested that the Cu²⁺ adsorption onto IIP-Cu had a good affinity at the solid-liquid surface. The efficiency of the prepared IIP-Cu was also tested by studying the adsorption capacity using Sr²⁺ and real brine water. The results revealed that IIP-Cu was able to remove 63.57% of Sr²⁺ at pH 8. While the adsorption studies revealed that the experiment was best described using the Langmuir model with a maximum adsorption capacity of 76.92 mg/g. Additionally, IIP-Cu was applied in a real brine sample, which consisted of various metal ions. The highest percentage of Cu²⁺ removal was 90.6% and the lowest was 65.63% in 1:4 and 1:1 brine ratios, respectively. However, this study indicates the successful application of IIP-Cu in a real sample when it comes to the effective and efficient removal of Cu²⁺ in a solution consisting of various competing ions.

Effective Adsorption and Removal of Doxorubicin from Aqueous Solutions Using Mesostructured Silica Nanospheres: Box-Behnken Design Optimization and Adsorption Performance Evaluation

The aim of this study is to evaluate the efficacy of mesoporous silica nanospheres as an adsorbent to remove doxorubicin (DOX) from aqueous solution. The surface and structural properties of mesoporous silica nanospheres were investigated using BET, SEM, XRD, TEM, ζ potential, and point of zero charge analysis. To optimize DOX removal from aqueous solution, a Box-Behnken surface statistical design (BBD) with four times factors, four levels, and response surface modeling (RSM) was used. A high amount of adsorptivity from DOX (804.84 mg/g) was successfully done under the following conditions: mesoporous silica nanospheres dose = 0.02 g/25 mL; pH = 6; shaking speed = 200 rpm; and adsorption time = 100 min. The study of isotherms demonstrated how well the Langmuir equation and the experimental data matched. According to thermodynamic characteristics, the adsorption of DOX on mesoporous silica nanospheres was endothermic and spontaneous. The increase in solution temperature also aided in the removal of DOX. The kinetic study showed that the model suited the pseudo-second-order. The suggested adsorption method could recycle mesoporous silica nanospheres five times, with a modest reduction in its ability for adsorption. The most important feature of our adsorbent is that it can be recycled five times without losing its efficiency.

Valorization of biowastes for clean energy production, environmental depollution and soil fertility

The mother earth is a source of natural resources that, in conjunction with anthropogenic activities, generates a wide spectrum of different biowastes. These biomaterials can be used as low-cost raw feedstock to produce bioenergy, value-added products, and other commodities. However, the improper management and disposal of these biowastes can generate relevant environmental impacts. Consequently, it is imperative to explore alternative technologies for the valorization and exploitation of these wastes to obtain benefits for the society. This review covers different aspects related to valorization of biowastes and their applications in water pollution, soil fertility and green energy generation. The classification and characteristics of different biowastes (biosolids, animal wastes and effluents, plant biomass, wood and green wastes) including their main generation sources are discussed. Different technologies (e.g., pyrolysis, hydrothermal carbonization, anaerobic digestion, gasification, biodrying) for the transformation and valorization of these residues are also analyzed. The application of biowastes in soil fertility, environmental pollution and energy production are described and illustrative examples are provided. Finally, the challenges related to implement low-cost and sustainable biowaste management strategies are highlighted. It was concluded that reliable simulation studies are required to optimize all the logistic stages of management chain of these residues considering the constraints generated from the economic, environmental and social aspects of the biowaste generation sources and their locations. The recollection and sorting of biowastes are key parameters to minimize the costs associated to their management and valorization. Also, the concepts of Industry 4.0 can contribute to achieve a successful commercial production of the value-added products obtained from the biowaste valorization. Overall, this review provides a general outlook of biowaste management and its valorization in the current context of circular economy.

Sustainability for wastewater treatment: bioelectricity generation and emission reduction

This review covers the technological measures of a self-sustainable anaerobic up-flow sludge blanket (UASB) system compared with an aerobic activated sludge process (ASP) for wastewater treatment plants (WWTPs). The ASP requires a huge amount of electricity and chemicals and also results in the emission of carbon. The UASB system, instead, is based on greenhouse gas (GHG) emission reduction and is associated with biogas production for cleaner electricity. WWTPs including the ASP system are not sustainable due to the massive financial power required for clean wastewater. When the ASP system was used, the amount of production was estimated to be 10658.98 tonnes CO₂eq-d^- of carbon dioxide. Whereas it was 239.19 tonnes CO₂eq-d^-1 with the UASB. The UASB system is advantageous over the ASP system as it has a high production of biogas, needs low maintenance, yields a low amount of sludge, and is also a source of electricity that can be used as a power source for the WWTPs. Also, the UASB system produces less biomass, and this helps in reducing costs and maintaining work. Moreover, the aeration tank of the ASP needs 60% of energy distribution; on the other hand, the UASB consumes less energy, approximately 3-11%.

Municipal Sewage Sludge as a Source for Obtaining Efficient Biosorbents: Analysis of Pyrolysis Products and Adsorption Tests

In the 21st century, the development of industry and population growth have significantly increased the amount of sewage sludge produced. It is a by-product of wastewater treatment, which requires appropriate management due to biological and chemical hazards, as well as several legal regulations. The pyrolysis of sewage sludge to biochar can become an effective way to neutralise and use waste. Tests were carried out to determine the effect of pyrolysis conditions, such as time and temperature, on the properties and composition of the products obtained and the sorption capacity of the generated biochar. Fourier transform infrared analysis (FTIR) showed that the main components of the produced gas phase were CO₂, CO, CH₄ and to a lesser extent volatile organic compounds. In tar, compounds of mainly anthropogenic origin were identified using gas chromatography mass spectrometry (GC-MS). The efficiency of obtaining biochars ranged from 44% to 50%. An increase in the pyrolysis temperature resulted in a decreased amount of biochar produced while improving its physicochemical properties. The biochar obtained at high temperatures showed the good adsorption capacity of Cu²⁺ (26 mg·g^-1) and Zn²⁺ (21 mg·g^-1) cations, which indicates that it can compete with similar sorbents. Adsorption of Cu²⁺ and Zn²⁺ proceeded according to the pseudo-second-order kinetic model and the Langmuir isotherm model. The biosorbent obtained from sewage sludge can be successfully used for the separation of metal cations from water and technological wastewater or be the basis for producing modified and mixed carbon sorbents.

Magnetic layered double hydroxide composite as new adsorbent for efficient Cu (II) and Ni (II) ions removal from aqueous samples: Adsorption mechanism investigation and parameters optimization

In this work, the magnetic layered double hydroxide composite as a new adsorbent was synthesized and applied for efficient copper (II) and nickel (II) ions removal from aqueous samples. After fabrication, the adsorbent was identified and characterized via Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy and vibrating sample magnetometer (VSM), while FE-SEM reveals and denote layered structure of present adsorbent. The magnetic strength of 20.34 emu g^-1 supplies sufficient magnetic property which leads to a solution fast separation of the adsorbent from the sample solution by an external magnet. Then, central composite design (CCD) based on response surface methodology (RSM) was used to optimize the effects of various parameters on the removal process and accordingly best operational conditions was fixed at: 0.039 g of adsorbent, 6.31 min sonication, pH (8) and 17 mgl^-1 of both copper (II) and nickel (II) ions concentrations, respectively. Moreover, the "Lack of Fit p-values" of analysis of variance were obtained to be 0.3758 and 0.8750 for nickel (II) and copper (II) ions, respectively which is not significant value denoting suitability of the current model. Amongst different isotherm and kinetic models, the current adsorption process followed the Freundlich and pseudo-second-order models, while the criterion for judgment is based on their higher correlation coefficients (more than 0.9) compared to other models. Kinetic judgment is based on the closeness of experimental and theoretical adsorption capacity and higher R² values. The Freundlich model based on the multilayer process occurs owing to the adsorption of ions onto the heterogeneous surface of the adsorbent. The adsorbent showed the maximum adsorption capacities of 200.00 mg g^-1 and 109.92 mg g^-1 for Cu²⁺ and Ni²⁺ ions, respectively. Experimental results explore that the chemical and electrostatic interactions were responsible for the under-study model ions. The relative standard deviations assign to both metal ions adsorption was 1.63-3.78% representing the applicability of the composite for practical purposes.

Influence of Fe2O3 and bacterial biofilms on Cu(II) distribution in a simulated aqueous solution: A feasibility study to sediments in the Pearl River Estuary (PR China)

This study investigated physico-chemical interactions among Cu(II), biogenic materials, and Fe₂O₃ in a continuous-flow biofilm reactor system under a well-controlled environment. The effects of Fe₂O₃ and bacterial biofilms on the distribution of Cu(II) in a simulated aquatic environment were studied. To control biological and abiotic elements in the marine environment, a biofilm reactor was designed to understand the metal speciation of Cu(II) and its distribution. The reactor consisted of a biofilm chamber equipped with glass slides for biofilms attachment. Due to its ability to grow as biofilm in the medium, Pseudomonas atlantica was cultivated to adsorb trace Cu(II) to attached and suspended cells. It was found that biofilms with 170-285 mequiv chemical oxygen demand (COD) concentration/m² of total oxidizable materials accelerated the Cu(II) adsorption to the surface of the reactor significantly by a factor of five. A significant inhibition to the bacterial growth took place (p ≤ 0.05; t-test) when Cu(II) concentration was higher than 0.5 mg/L. In the absence of Cu(II), bacterial cells grew normally to 0.075 of optical density (OD). However, at the Cu(II) concentration of 0.2 mg/L, the cells grew to a lower OD of 0.58. The presence of glycine and EDTA substantially reduced the toxicity of Cu(II) on bacterial growth (p ≤ 0.05; paired t-test). Their complexation with Cu(II) rendered the metal ions less available to bacterial cells. This implies that the Fe₂O₃ and bacterial biofilm affected Cu(II) distribution and speciation in the aquatic environment.

Enhanced Adsorption and Evaluation of Tetracycline Removal in an Aquatic System by Modified Silica Nanotubes

In the present study, a nanocomposite adsorbent based on mesoporous silica nanotubes (MSNTs) loaded with 3-aminopropyltriethoxysilane (3-APTES@MSNTs) was synthesized. The nanocomposite was employed as an effective adsorbent for the adsorption of tetracycline (TC) antibiotics from aqueous media. It has an 848.80 mg/g maximal TC adsorption capability. The structure and properties of 3-APTES@MSNT nanoadsorbent were detected by TEM, XRD, SEM, FTIR, and N₂ adsorption-desorption isotherms. The later analysis suggested that the 3-APTES@MSNT nanoadsorbent has abundant surface functional groups, effective pore size distribution, a larger pore volume, and a relatively higher surface area. Furthermore, the influence of key adsorption parameters, including ambient temperature, ionic strength, initial TC concentration, contact time, initial pH, coexisting ions, and adsorbent dosage, had also been investigated. The 3-APTES@MSNT nanoadsorbent's ability to adsorb the TC molecules was found to be more compatible with Langmuir isothermal and pseudo-second-order kinetic models. Moreover, research on temperature profiles pointed to the process' endothermic character. In combination with the characterization findings, it was logically concluded that the 3-APTES@MSNT nanoadsorbent's primary adsorption processes involved interaction, electrostatic interaction, hydrogen bonding interaction, and the pore-fling effect. The synthesized 3-APTES@MSNT nanoadsorbent has an interestingly high recyclability of >84.6 percent up to the fifth cycle. The 3-APTES@MSNT nanoadsorbent, therefore, showed promise for TC removal and environmental cleanup.

Heavy metals reshaping the structure and function of phylloplane bacterial community of native plant Tamarix ramosissima from Pb/Cd/Cu/Zn smelting regions

Heavy metal (HM) is noxious element that cannot be biodegraded, thus accumulating in the environment and posing a serious threat to the ecology. Plant phylloplane harbors diverse microbial communities that profoundly influence ecosystem functioning and host health. With more HM accumulating around smelters, native plants and microbes in various habitats tend to suffer from HM. However, the response of phylloplane bacteria of native plants to HM remains unclear. Thus, this study aimed to explain the response of Tamarix ramosissima, a phylloplane bacterial community to HM as well as the effect of the process on host growth in situ by investigating the potential source of HM and bacterial community shift. Results showed that, in most cases, the contaminated site with high HM level caused more accumulation of HM in phylloplane and leaves. Moreover, HM in the phylloplane was not from the internal transport of the plant but it could be due to the wind action or rains. Bacteria in phylloplane may have come from the soil due to their strong positive correlation with corresponding soil at the genus level. High HM level inhibited the relative abundance of dominant bacteria, increased the diversity and species richness of bacterial community in phylloplane, and induced more special bacteria to maintain higher productivity of the host plant, for which, Cu and Pb were the major contributors. Meanwhile, bacteria in phylloplane showed a universal positive correlation in the co-occurrence network, which showed less stability than that in corresponding soil in the smelting region, and it is helpful to regulate the growth of plants more rapidly. Nearly 25% of KEGG pathways were modulated by high HM level and bacterial function tended to stabilize HM to avoid the potential process of leaf absorption. The study illustrated that HM in phylloplane played an important role in shaping the bacterial community of phylloplane as compared to HM in leaves or phyllosphere, and the resulting increase of diversity and richness of bacterial community and special bacteria further maintained the growth of the host plant suffering from HM stress.

Regeneration mechanism of a novel high-performance biochar mercury adsorbent directionally modified by multimetal multilayer loading

Biochar that is directly obtained by pyrolysis exhibits a low adsorption efficiency; furthermore, the process of recycling adsorbents is ineffective. To solve these problems, conventional chemical coprecipitation, sol-gel, multimetal multilayer loading and biomass pyrolysis coking processes have been integrated. After selecting specific components for structural design, a novel high-performance biochar adsorbent was obtained. The effects of the O₂ concentration and temperature on the regeneration characteristics were explored. An isothermal regeneration method to repair the deactivated adsorbent in a specific atmosphere was proposed, and the optimal regeneration mode and conditions were determined. The microscopic characteristics of the regenerated samples were revealed along with the mechanism of Hg⁰ removal and regeneration by using temperature-programmed desorption technology and adsorption kinetics. The results show that doping multiple metals can reduce the pyrolysis reaction barrier of the modified biomass. On the modified surface of the sample, the doped metals formed aggregated oxides, and the resulting synergistic effect enhanced the oxidative activity of the biochar carriers and the threshold effect of Ce oxide. The optimal regeneration conditions (5% O₂ and 600 °C) effectively coordinated the competitive relationship between the deep carbonization process and the adsorption/oxidation site repair process; in addition, these conditions provided outstanding structure-effect connections between the physico-chemical properties and Hg⁰ removal efficiency of the regenerated samples. Hg⁰ adsorption by the regenerated samples is a multilayer mass transfer process that involves the coupling of physical and chemical effects, and the surface adsorption sites play a leading role.

Efficient Removal of Ciprofloxacin from Contaminated Water via Polystyrene Anion Exchange Resin with Nanoconfined Zero-Valent Iron

Ciprofloxacin (CIP), an important emerging contaminant, has been frequently detected in water, and its efficient removal has become an issue of great concern. In this study, a nanocomposite material nZVI/PA was synthesized by impregnating nanoscale zero-valent iron (nZVI) inside a millimeter-sized porous host (polystyrene-based anion exchange resin (PA)) for CIP removal. The nZVI/PA composite was characterized by field emission scanning electron microscopy coupled with energy-dispersive X-ray, transmission electron microscopy, X-ray diffraction, as well as X-ray photoelectron spectroscopy, and it was confirmed that nZVI was uniformly dispersed in PA with a small particle size. Furthermore, several key factors were investigated including initial solution pH, initial CIP concentration, co-existing ions, organic ligands, and dissolved oxygen. The experimental results indicated that the nZVI/PA composites exhibited a high removal efficiency for CIP under the conditions of initial pH 5.0, and initial CIP concentration 50 mg L^-1 at 25 °C, with the maximum removal rate of CIP reaching 98.5%. Moreover, the nZVI/PA composites exhibited high efficiency even after five cycles. Furthermore, quenching tests and electron spin resonance (ESR) confirmed that CIP degradation was attributed to hydroxyl (·OH) and superoxide radicals (⋅O2-). Finally, the main degradation products of CIP were analyzed, and degradation pathways including the hydroxylation of the quinolone ring, the cleavage of the piperazine ring, and defluorination were proposed. These results are valuable for evaluating the practical application of nZVI/PA composites for the removal of CIP and other fluoroquinolone antibiotics.

Biosorption of heavy metals from aqueous solutions using activated sludge, Aeromasss hydrophyla, and Branhamella spp based on modeling with GEOCHEM

This work tests the technical applicability of sewage sludge and isolated dead cells of Aeromasss hydrophyla and Branhamella spp for the elimination of inorganic pollutants such as Zn(II), Pb(II), Cd(II), and/or Cu(II) using synthetic wastewater with their initial concentrations of 100 mg/L, respectively. The sludge samples were collected from local sewage treatment plants. The effects of dose and pH on heavy metals removal were evaluated in batch studies and their removal performances were compared to those of previous studies. Both the Freundlich and the Langmuir models were plotted to study their biosorption using activated sludge and the bacteria. Isotherm data, resulting from the batch studies, were compared to the modeling results of Geochem. It was evident that the activated sludge could achieve 99% of Zn(II), Cd(II), Cu(II) and Pb(II) removal with 100 mg/L of concentration at pH 6.0 and 3 g/L of dose. Under the same conditions, 97% of Cd(II), Cu(II) and/or Pb(II) was removed by Aeromasss hydrophyla and Branhamella spp, as indicated by their adsorption capacities (activated sludge: 99.07 mg Pb²⁺/g; dewatered sludge: 57.15 mg Pb²⁺/g; digested sludge: 83.58 mg Pb²⁺/g; 24.47 mg Cd²⁺/g; Aeromasss hydrophylla: 71.91 mg Pb²⁺/g; Branhamella spp: 37.52 mg Cu²⁺/g). Of the four heavy metals studied, Pb(II) had the highest metal adsorption capacity for all adsorbents studied (Pb²⁺>Cu²⁺> Cd²⁺>Zn²⁺). The modeling results of the Geochem fitted well with the isotherm data of the batch studies at varying concentrations from 20 to 100 mg/L. The thermodynamic constant at pH 4 were comparable to those obtained from previous works. This indicates a reliable prediction over varying metal concentrations and pHs of the batch studies. In spite of the promising results, the treated effluents still could not meet the required effluent limits set by local legislation. Therefore, it is necessary to subsequently treat the samples using biological processes such as activated sludge.