Synthesis of magnetic alginate hybrid beads for efficient chromium (VI) removal

Biosynthesis and Mathematical Interpretation of Zero-Valent Iron NPs Using Nigella sativa Seed Tincture for Indemnification of Carcinogenic Metals Present in Industrial Effluents

Zero-valent iron nanoparticles (ZVI-NPs) are utilized for the indemnification of a wide range of environmental pollutants. Among the pollutants, heavy metal contamination is the major environmental concern due to their increasing prevalence and durability. In this study, heavy metal remediation capabilities are determined by the green synthesis of ZVI-NPs using aqueous seed extract of Nigella sativa which is a convenient, environmentally friendly, efficient, and cost-effective technique. The seed extract of Nigella sativa was utilized as a capping and reducing agent for the generation of ZVI-NPs. UV-visible spectrophotometry (UV-vis), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared spectroscopy (FTIR) was used to investigate the ZVI-NP composition, shape, elemental constitution, and perspective functional groups, respectively. The biosynthesized ZVI-NPs displayed a peak of plasmon resonance spectra at 340 nm. The synthesized NPs were cylindrical in shape, with a size of 2 nm and (-OH) hydroxyl, (C-H) alkanes and alkynes N-C, N=C, C-O, =CH functional groups attached to the surface of ZVI-NPs. Heavy metals were successfully remediated from industrial wastewater collected from the various tanneries of Kasur. During the reaction duration of 24 h, different concentrations of ZVI-NPs (10 μg, 20 μg and 30 μg) per 100 mL were utilized for the removal of heavy metals from industrial wastewater. The 30 μg/100 mL of ZVI-NPs proved the pre-eminent concentration of NPs as it removed >90% of heavy metals. The synthesized ZVI-NPs were analyzed for compatibility with the biological system resulting in 87.7% free radical scavenging, 96.16% inhibition of protein denaturation, 60.29% and 46.13% anti-cancerism against U87-MG and HEK 293 cell lines, respectively. The physiochemical and exposure mathematical models of ZVI-NPs represented them as stable and ecofriendly NPs. It proved that biologically synthesized NPs from a seed tincture of Nigella sativa have a strong potential to indemnify heavy metals found in industrial effluent samples.

The adsorbent preparation of FeOOH@PU for effective chromium (VI) removal

A novel adsorbent (FeOOH@PU) for hexavalent chromium [Cr(VI)] removal was synthesized using a polyurethane foam (PU) and FeOOH via a facile one-step method. Scanning electron microscopy (SEM), FTIR, X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS) characterized the adsorbent. The influence of environmental factors was investigated to evaluate the adsorption behavior for Cr(VI). Furthermore, adsorption dynamic and adsorption isotherm models described the adsorption performance. This adsorbent also treated electroplating wastewater and remediated simulated Cr(VI) contaminated soil. The adsorbent effectively removed Cr(VI) with a high adsorption rate; its equilibrium rate constant was 13 times that of FeOOH. Cr(VI) removal was a monolayer adsorption process and the maximum adsorption capacity of FeOOH@PU reached 34.9 mg Cr/g. Electrostatic attraction was the mechanism of Cr(VI) removal. Electroplating wastewater became clear and the Cr(VI) concentration decreased from 9.76 to 0.042 mg/L after treatment with FeOOH@PU. Cr enrichment in rice seedlings grown in remediated soil decreased from 7.687 to 6.295 mg Cr/kg. These results suggested that FeOOH@PU was a promising adsorbent for Cr(VI) removal and Cr(VI) stabilization.

Facile construction of cost-effective zinc-aluminium polymeric framework for efficient removal of selective both drug and dye from an aqueous medium

A novel aluminium (Al) and its active alloys are extensively been used in nearly all areas owing to their cost-effectiveness. But when it is subjected to an aqueous medium, gets corroded through a chemical response. In this paper, a novel framework was fabricated by copolymer coating over on Al and loaded with zinc via electro polymerization and electrodeposition method ([EDA- OPDA]Al@Zn). The as-fabricated composite has emerged for the sorption of Methylene Blue (MB) aqueous dye and Paracetomal drug (PAR). The as-fabricated composite framework has been categorized via IR spectra, FE-SEM images, and EDX spectra. The sorption progression was optimized for numerous prompting features like pH, contact time and impact of dosage. Based on kinetics data, the growth in QE value by an enhancement in temperature for adsorption and the higher r values shows the adsorption progression is a pseudo-second-order model. The thermodynamic constraints specify that the field of adsorbate is impulsive and typical endothermic process. Instead, the corrosion resistance of a composite in the 3.5% of NaCl. Solution was explored via EIS spectra and potentio-dynamic polarization. Depending on the observed features, it indicates that the [EDA-OPDA]Al@Zn framework provided fantastic corrosion resistance. So it is obvious that the as-synthesized framework is of multitasking, that it could be successfully performed for the exclusion of MB aqueous dye and PAR drug from the aqueous medium and it also withstands effectively in this corrosive medium.

Evaluation of Heavy Metal Removal of Nanoparticles Based Adsorbent Using Danio rerio as Model

Nanoparticles are potential candidates for wastewater treatment especially for the removal of heavy metals due to their strong affinity. Many biopolymers are used as adsorbents and encapsulation of nanoparticle onto them can increase their efficiency. In this study, SPIONs, alginate, and SPIONs incorporated on alginate beads have been synthesized and characterized both microscopically and spectroscopically. These were then used for the removal of chromium metal and the percentage of removal was evaluated using a batch adsorption study. The percent removal of chromium using SPIONs, alginate and alginate-SPIONs beads were recorded to be 93%, 91% and 94%, respectively. The adsorption of chromium using SPIONs and alginate-SPIONs beads followed the Tempkin isotherm, whereas adsorption of chromium metal by alginate beads was found to be homogeneous in nature and followed the Langmuir isotherm with an R² value of 0.9784. An in-vivo study using Danio rerio as a model organism was done to examine the toxicity and the removal efficiency of the samples. It was observed that chromium water treated with alginate-SPIONs beads, which were removed after water treatment showed less damage to the fishes when compared to SPIONs and alginate beads treated with chromium water where the SPIONs and alginate beads were not removed after the treatment period.

Synthesis of Biomass-Derived Activated Carbons and Their Immobilization on Alginate Gels for the Simultaneous Removal of Cr(VI), Cd(II), Pb(II), As(III), and Hg(II) from Water

Low-cost alginate gels of activated carbons were prepared, which were derived from the peels of banana and sweet lime. The synthesized carbon was activated and immobilized on alginate, producing its gel. These gels were categorized according to their methods of drying, in which air drying, freeze drying, and supercritical drying led to the formation of xerogels, cryogels, and aerogels, respectively. The gels were used for adsorption of heavy metals from their aqueous solution. The heavy metals that were targeted for removal were Pb(II), Cd(II), Cr(VI), As(III), and Hg(II). Among all the adsorbents, the alginate cryogel of sweet lime-derived activated carbon (SLACC) showed the highest removal percentage of heavy metals, and thus, it was used for batch study. The adsorption of heavy metals by SLACC was checked at different times, pH values, adsorbent doses, temperatures, and adsorbate concentrations. The study revealed that the pseudo-second-order model best described the kinetic study, while the adsorption followed the Freundlich isotherm. SLACC showed maximum adsorption capacities (q _cal) of 3.71, 4.22, 20.04, 7.31, and 4.37 mg/g for Cr, Cd, Pb, As, and Hg, respectively, when 20 mg of SLACC was used for the removal of 4 ppm concentration of the targeted heavy metals from their 20 mL solution. Based on the thermodynamic study, it was found that the adsorption was spontaneous and exothermic. Furthermore, the adsorbent was also used on real water samples and showed up to 90% removal efficiency for these targeted heavy metals. SLACC was regenerated with 0.1 M ethylenediaminetetraacetic acid (EDTA) solution and reused for five cycles, in which the percentage removal of heavy metals was more than 50% till the fourth cycle. Furthermore, the leaching study showed that no toxic elements had leached from SLACC into water, making it a safe adsorbent.

Plant-Derived Iron Nanoparticles for Removal of Heavy Metals

Nanoparticle synthesis has seen exponential development recently as its characteristics of high surface area, high rate of adsorption, and easy, cost-effective synthesis have been exploited for the purpose of ground water purification via the removal of organic and inorganic compounds, along with the removal of heavy metals and microbes. The synthesis of Zero-Valent Iron Nanoparticles (ZVI NPs) by green methods has proved to be environmentally friendly in many ways as it employs the use of naturally occurring plant extracts. These nanoparticles have large surface areas and efficiently remove heavy metals. The reducing potential of these ZVI NPs is mostly −0.44 V, thus allowing them to reduce heavy metal compounds such as cadmium, lead, zinc, copper, and arsenic present in wastewater. Irradiated nanoparticles have also exhibited antimicrobial resistance and adsorption. It is also observed that nanoparticles show a higher rate of efficacy at a lower pH. The adsorbent, which is ZVI NPs in this case, when present in large doses reduces heavy metal compounds rapidly and effectively.

Portable SA/CMC entrapped bimetallic magnetic fly ash zeolite spheres for heavy metals contaminated industrial effluents treatment via batch and column studies

Heavy metals are perceived as a significant environmental concern because of their toxic effect, bioaccumulation, and persistence. In this work, a novel sodium alginate (SA) and carboxymethylcellulose (CMC) entrapped with fly ash derived zeolite stabilized nano zero-valent iron and nickel (ZFN) (SA/CMC-ZFN), followed by crosslinking with CaCl₂, is synthesized and applied for remediation of Cu(II) and Cr(VI) from industrial effluent. The characterization of the adsorbent and its surface mechanism for removing metals were investigated using advanced instrumental techniques, including XRD, FT-IR, SEM–EDX, BET, and XPS. The outcomes from the batch experiments indicated that monolayer adsorption on homogeneous surfaces (Langmuir isotherm model) was the rate-limiting step in both heavy metals sorption processes. The maximum adsorption capacity of as-prepared SA/CMC-ZFN was 63.29 and 10.15 mg/g for Cu(II) and Cr(VI), respectively. Owing to the fact that the wastewater released from industries are large and continuous, a continuous column is installed for simultaneous removal of heavy metal ions from real industrial wastewater. The outcomes revealed the potential of SA/CMC-ZFN as an efficient adsorbent. The experimental breakthrough curves fitted well with the theoretical values of Thomas and Yoon-Nelson models. Overall, the results indicated that SA/CMC-ZFN is a viable, efficient, and cost-effective water treatment both interms of batch and column processes.

An Overview on Composite Sorbents Based on Polyelectrolytes Used in Advanced Wastewater Treatment

Advanced wastewater treatment processes are required to implement wastewater reuse in agriculture or industry, the efficient removal of targeted priority and emerging organic & inorganic pollutants being compulsory (due to their eco-toxicological and human health effects, bio-accumulative, and degradation characteristics). Various processes such as membrane separations, adsorption, advanced oxidation, filtration, disinfection may be used in combination with one or more conventional treatment stages, but technical and environmental criteria are important to assess their application. Natural and synthetic polyelectrolytes combined with some inorganic materials or other organic or inorganic polymers create new materials (composites) that are currently used in sorption of toxic pollutants. The recent developments on the synthesis and characterization of composites based on polyelectrolytes, divided according to their macroscopic shape-beads, core-shell, gels, nanofibers, membranes-are discussed, and a correlation of their actual structure and properties with the adsorption mechanisms and removal efficiencies of various pollutants in aqueous media (priority and emerging pollutants or other model pollutants) are presented.

Facile green synthesis of zero-valent iron nanoparticles using barberry leaf extract (GnZVI@BLE) for photocatalytic reduction of hexavalent chromium

In this study, zero-valent iron (GnZVI) was synthesized using barberry leaf extract (GnZVI@BLE). The physicochemical properties of the final products were characterized by FT-IR, SEM, TEM, and EDS techniques. The results of TEM analysis showed that the obtained iron zero-valent nanoparticles with a diameter between 20 and 40 nm and shell-core structures were successfully synthesized. The results of FT-IR confirmed the presence of various functional groups. The photocatalytic activity of synthesized nanoparticles was investigated by reduction of hexavalent chromium. Laboratory data showed that the presence of GnZVI@BLE as a nanocatalyst in the photocatalytic process could be reduction the hexavalent chromium (Cr (VI)). Photocatalytic data revealed that, when the dosage of nanoparticles was 0.675 g/L, the reduction efficiency of hexavalent chromium was 100%. The kinetics of the reaction follows a pseudo-second-order equation. The constant of reaction rate was 0.4 at pH 2 and 0.5 g/L concentration of GnZVI@BLE.

Synthesis of an Alginate-Based Fe3O4-MnO2 Xerogel and Its Application for the Concurrent Elimination of Cr(VI) and Cd(II) from Aqueous Solution

In this study, magnetite-manganese oxide (Fe₃O₄-MnO₂) nanoparticles were synthesized and immobilized on alginate, producing a magnetite-manganese oxide xerogel (mMOX). This eco-friendly xerogel was used as an adsorbent of Cr(VI) and Cd(II). It was mesoporous and thermally stable, as determined by Brunauer-Emmett-Teller and thermogravimetric analysis. A scanning electron microscope coupled with an energy-dispersive X-ray system, Zetasizer, and attenuated total reflectance-Fourier transform infrared were used for characterization of adsorbents. The performance of the mMOX was investigated for the simultaneous adsorption of Cr(VI) and Cd(II) at different temperatures, pH values, contact times, initial concentrations of the adsorbate, and adsorbent doses. The developed xerogel (mMOX) showed high adsorption capacities of 3.86 mg/g for Cr(VI) and 3.95 mg/g for Cd(II) on 120 min of contact time with 5 ppm Cr(VI) and Cd(II) solution. The kinetic data fitted well with the pseudo-second order, while the Freundlich isotherm model was found to be fit for adsorption data. Thermodynamic study revealed the adsorption to be spontaneous and exothermic. The adsorbent showed useful application for real water samples by more than 75% uptake of Cr and Cd with low adsorption of Na, K, and Mg. The regeneration study indicated that the mMOX could be reused up to six cycles with more than 50% removal of Cr(VI) and Cd(II) ions from aqueous solution with minimal leaching of metal ions (Fe, Ca, Na, K, and Mn) into the solution.

Development of triaminotriazine functionalized graphene oxide capped chitosan porous composite beads for nutrients remediation towards water purification

The porous, definite and nitrogen rich triaminotriazine (TAT) grafted graphene oxide (GO) known as TATGO composite was developed for nutrients (NO₃^- and PO₄^3-) retention. Additionally, the structural property of TATGO composite was improved with the use of chitosan (CS) to produce easily separable TATGO@CS hybrid beads which possess the significant NO₃^- and PO₄^3- adsorption capacities of 58.46 and 61.38 mg/g respectively than their individual materials. The instrumentations such as SEM, TGA, FTIR, EDAX, XRD and BET studies were executed for adsorbents. The optimization of the parameters accountable for adsorption process was performed in batch scale. The effect of isotherms (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)), kinetics (pseudo-first/second order and particle/intraparticle diffusion) and thermodynamic parameters (ΔG°, ΔH° and ΔS°) of the adsorption was explored. The removal mechanism of TATGO@CS hybrid beads was to be electrostatic attraction on NO₃^- and PO₄^3-. The field applicability and reuse of TATGO@CS hybrid beads was also inspected.

Novel synthesis of Ni/Fe layered double hydroxides using urea and glycerol and their enhanced adsorption behavior for Cr(VI) removal

Novel modified Ni/Fe layered double hydroxides with different morphology of spherical - like shape were fabricated via using urea as a ligand and glycerol (Ni/Fe LDH/GL) with Ni:Fe molar ratios of 2:1 by the simplest co -precipitation method. Also, for comparison purposes, Ni/Fe LDH was synthesized to be used as a control one. A suggested interpretation for the morphology change was also given. The materials were characterized by X-ray diffraction (XRD), The Fourier transform infrared (FT - IR) spectroscopy, field emission scanning electron microscopy (FESEM), EDX for elemental analysis, high resolution transmission electron microscopy (HRTEM), Brunauer, Emmett, and Teller (BET) equation, particle size distributions and Zeta potential measurements. In addition, the synthesized materials were used as adsorbents for removal of potassium dichromate from aqueous solutions under various experimental conditions. The adsorption of Cr (VI) was strongly pH dependant and the pH_PZC was studied. Kinetic studies were evaluated through different models including, pseudo first and second orders, mixed 1, 2 orders, intra particle diffusion and Avrami models. For adsorption isotherms, two-parameter models (Langmuir, Freundlich and Temkin) and three parameter models (Sips, Langmuir-Freundlich and Tooth) were investigated showing maximum adsorption capacity of 50.43 mg/g and 136.05 mg/g for Ni/Fe LDH and Ni/Fe LDH/GL, respectively. Also, the effect of temperature was investigated at (23, 35, 45, 55 °C) and the thermodynamic parameters (∆H°, ∆S° and ∆G°) were calculated showing exothermic and spontaneous adsorption process. The effect of coexisting anions (Cl^-, SO₄^2- and HPO₄^2-) and humic acid at different concentrations on the removal efficiency of dichromate ions was investigated. Chemical stability and recyclability of these adsorbents were also studied. The intermolecular hydrogen bonds formation between dichromate ion, urea, glycerol, LDH was explored by Monte Carlo simulation This study suggested that the modified Ni/Fe LDH/GL materials were promising nanoadsorbents for efficient potassium dichromate removal.

Eco-friendly porous carboxymethyl cellulose/dextran sulfate composite beads as reusable and efficient adsorbents of cationic dye methylene blue

Eco-friendly hydrogel composite beads based on crosslinked-carboxymethyl cellulose (CMC) and dextran sulfate (DS) embedded within network were prepared using ionotropic gelation in presence of sodium n-dodecyl sulfate (SDS) as pore-forming template. The milligels composites C/Dx were characterized by FTIR, SEM/EDX and TGA analyses. The composites exhibited porous structure and enhance in swelling properties with enriching DS as well as pH-sensitivity. The effect of DS on adsorption of composites for cationic dye methylene blue (MB) was investigated by changing influencing factors: pH, adsorbent dosage, time contact, dye concentration, and temperature. The results revealed that adsorption performances were remarkably improved by increasing DS content into beads. Kinetics and isotherm adsorption studies revealed pseudo second-order and Langmuir isotherm as befitting models. The maximum Langmuir equilibrium adsorption capacity (q_m) was found to increase from 82 mg g^-1 for C/D0 to 526 mg g^-1 for C/D1. Thermodynamic study revealed spontaneous and endothermic process nature. Furthermore, milligels displayed good reusability after five adsorption/desorption cycles and with an augment in their removal ability compared to starting ones, reaching 714 mg g^-1 for R-C/D1. In view of easy preparation and recovery, effectiveness adsorption and good regeneration, the composites could be applied as low-cost adsorbents in wastewater treatment.

Alginate-based composites for environmental applications: A critical review

Alginate-based composites have been extensively studied for applications in energy and environmental sectors due to their biocompatible, nontoxic, and cost-effective properties. This review is designed to provide an overview of the synthesis and application of alginate-based composites. In addition to an overview of current understanding of alginate biopolymer, gelation process, and cross-linking mechanisms, this work focuses on adsorption mechanisms and performance of different alginate-based composites for the removal of various pollutants including dyes, heavy metals, and antibiotics in water and wastewater. While encapsulation in alginate gel beads confers protective benefits to engineered nanoparticles, carbonaceous materials, cells and microbes, alginate-based composites typically exhibit enhanced adsorption performance. The physical and chemical properties of alginate-based composites determine the effectiveness under different application conditions. A series of alginate-based composites and their physicochemical and sorptive properties have been summarized. This critical review not only summarizes recent advances in alginate-based composites but also presents a perspective of future work for their environmental applications.

Hydrothermal synthesis of hydrocalumite assisted biopolymeric hybrid composites for efficient Cr(vi) removal from water

Hydrocalumite (HC) incorporated biopolymer (alginate and chitosan) based hybrid composite materials were developed for the selective removal of chromium.

Combined effects of adsorption and photocatalysis by hybrid TiO2/ZnO-calcium alginate beads for the removal of copper

The use of nanosized titanium dioxide (TiO₂) and zinc oxide (ZnO) in the suspension form during treatment makes the recovering and recycling of photocatalysts difficult. Hence, supported photocatalysts are preferred for practical water treatment applications. This study was conducted to investigate the efficiency of calcium alginate (CaAlg) beads that were immobilized with hybrid photocatalysts, TiO₂/ZnO to form TiO₂/ZnO-CaAlg. These immobilized beads, with three different mass ratios of TiO₂:ZnO (1:1, 1:2, and 2:1) were used to remove Cu(II) in aqueous solutions in the presence of ultraviolet light. These beads were subjected to three cycles of photocatalytic treatment with different initial Cu(II) concentrations (10-80ppm). EDX spectra have confirmed the inclusion of Ti and Zn on the surface of the CaAlg beads. Meanwhile, the surface morphology of the beads as determined using SEM, has indicated differences of before and after the photocatalytic treatment of Cu(II). Among all three, the equivalent mass ratio TiO₂/ZnO-CaAlg beads have shown the best performance in removing Cu(II) during all three recycling experiments. Those TiO₂/ZnO-CaAlg beads have also shown consistent removal of Cu, ranging from 7.14-62.0ppm (first cycle) for initial concentrations of 10-80ppm. In comparison, bare CaAlg was only able to remove 6.9-48ppm of similar initial Cu concentrations. Thus, the potential use of TiO₂/ZnO-CaAlg beads as environmentally friendly composite material can be further extended for heavy metal removal from contaminated water.