Nanocomposite Beads Research Articles

Synthesis and Characterization of Ca-ALG/MgO/Ag Nanocomposite Beads for Catalytic Degradation of Direct Red Dye

Increased water pollution due to the tremendous increase of dye-containing effluent is still a serious problem which, in turn, adversely affects aquatic life and, consequently, the balance of our ecosystem. The aim of this research was to investigate whether Ca-ALG/MgO/Ag nanocomposite beads successfully prepared from calcium alginate hydrogels with MgO (Ca-ALG/MgO) doped with Ag nanoparticles (Ag NPs) caused effective degradation of Direct Red 83 dye. The formation of nanocomposite beads was confirmed by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), Dynamic Light Scattering (DLS), and Energy Dispersive X-ray Analysis (EDX). The results from the EDX analysis proved that both MgO and Ag nanoparticles within the alginate beads network were present. This study also examines the effects of various operating parameters, such as the reducing agent, time of reaction, the concentration of the dye solution, and the catalyst dosage, which were examined and studied carefully to find the optimum degradation conditions. The kinetics and isothermal study revealed that the degradation process using Ca-ALG/MgO/Ag nanocomposite beads as a catalyst in the presence of sodium borohydride (NaBH4) as a reducing agent was the best fit for the pseudo-first-order model and the Temkin isotherm model. The results indicated that the optimum dosage of Ca-ALG/MgO/Ag was 0.3 g for a dye concentration of 50 mg/L, and equilibrium of the degradation process was attained at 340 min. Accordingly, it could be stated that the catalyst, Ca-ALG/MgO/Ag nanocomposite beads, is considered efficient for the degradation of Direct Red 83 dye. The degradation efficiency reached 95% approximately. Furthermore, after four runs of reuse, Ca-ALG/MgO/Ag nanocomposite beads exhibited excellent performance and long-term stability.

Efficient nitrate reduction in water using an integrated photocatalyst adsorbent based on chitosan-titanium dioxide nanocomposite.

Globally, there exists a huge concern on the increased discharge of nitrates to the natural water resources out of various anthropogenic activities as it causes serious environmental pollution and associated harmful effects. In the present work, sol-gel-derived functional nanocomposites based on silver (Ag) and nitrogen (N)-doped titanium dioxide (TiO2)-coated chitosan nanocomposites were successfully synthesized in the form of beads, and their application for the reduction of nitrates in water was studied. The synthesized nanocomposite beads were characterized for their structural, textural, and morphological features using X-ray diffraction analysis, Fourier transform infrared spectroscopy, UV-visible spectroscopy, BET surface area analysis, Scanning electron microscopy, Transmission electron microscopy, and X-ray photoelectron spectroscopy. A uniform coating of doped titania species on the chitosan porous structure was achieved through electrostatic interaction. Adsorption/photocatalytic reduction of nitrates was further carried out using functional nanocomposite beads by monitoring the nitrate concentration of the model contaminated water, in an adsorption study under dark condition and photocatalytic study under UV/sunlight for a definite time period. Drying conditions of the nanocomposite beads were found to have a significant effect on the adsorption cum photocatalytic efficiencies of the nanocomposite. The freeze-dried chitosan-titania nanocomposite beads containing 0.5mol% Ag exhibited an adsorption efficiency of ~ 43.5% (under dark for 30min) and photocatalytic reduction capability of ~ 95% (under sunlight for 2h), whereas the oven dried beads of the same composition exhibits adsorption and photocatalytic efficiencies of 40% (under dark for 30min) and 70% (under UV light for 2h) respectively, towards the reduction of nitrate ions in an aqueous solution. Continuous flow adsorption cum photocatalytic study using the oven-dried nanocomposite beads was also carried out with the help of an experimental setup fabricated in-house and under varying experimental conditions such as flow rate, bed height, and concentration of feed solution. Nitrate reduction efficiency of 87.6% and an adsorption capacity of 7.9mgg-1 were obtained for the nanocomposite beads in the continuous flow adsorption cum photocatalysis experiment for up to 8h when using an inlet concentration of 100ppm, bed height 12cm, and flow rate 5.0mLmin-1. A representative fixed-bed column adsorption experiment performed with oven dried nanocomposite beads in a real groundwater sample collected from the Palakkad District of Kerala shows promising results for nitrate reduction (85.9% efficiency) along with a significant removal rate for the other anions as well. Thus, the adsorption cum photocatalytic nitrate reduction efficiency of the functional nanocomposite material makes them suitable for the reduction of nitrates from water/wastewater through an integrated nanocomposite approach.

Activated Charcoal/Alginate Nanocomposite Beads for Efficient Adsorption of the Cationic Dye Methylene Blue: Kinetics and Equilibrium

Activated Charcoal/Alginate Nanocomposite Beads for Efficient Adsorption of the Cationic Dye Methylene Blue: Kinetics and Equilibrium

Hydrogel Nanocomposite Adsorbents and Photocatalysts for Sustainable Water Purification

AbstractHydrogels have been employed for water purification applications, but their performance and strength are unsatisfactory for widespread adoption. Recently, hydrogel nanocomposites have been proposed to resolve the inherent challenges faced by hydrogels for water treatment. This review comprehensively analyzes hydrogel nanocomposites for water treatment using adsorbent and photocatalysis techniques. The structure, classification, and tunable synthesis methods of hydrogels are explained. Further, how hydrogels can be incorporated with functional nanoparticles (NPs) and can be used as templates/precursors for developing advanced 3D architectures, including the formation of hydrogel nanocomposite beads and 3D printing objects are discussed. Finally, the structure‐property relationships of hydrogel nanocomposites are critically reviewed by considering introductory gelation chemistry, such as swelling characteristics, mechanical properties, stimuli‐responsiveness, and ionic/electronic conduction. The extensive cross‐linking of polymer chains with NPs offers high mass/charge transport, high surface areas, and enhanced polymer‐water interactions to achieve high‐performing adsorbents and photocatalysts. Several motivating examples of emerging NP‐containing hydrogel nanocomposites for use in adsorbents and photocatalysis have been discussed. Such efforts validated the excellent technological potential held by hydrogel nanocomposites for water purification applications. Finally, future directions of hydrogel nanocomposites for sustainable water treatment are proposed.

Synthesis of sodium alginate/carboxy-methyl cellulose/Cu-based metal-organic framework composite for adsorption of tetracycline from aqueous solution: Isotherm, kinetic and thermodynamic approach

Sodium alginate/carboxy-methyl cellulose/Cu-based metal-organic framework (SA/CMC/Cu-BDC) nanocomposite beads were prepared using an ex-situ combination of natural bio-polymers and pre-synthesized Cu-BDC powder and freeze-drying. Several methods such as XRD, FTIR, EDX, SEM, and N2 adsorption-desorption were used to pinpoint the physical and chemical properties of as-prepared materials. Cu-BDC particles distributed in the interior porosity of two-biopolymeric composites as revealed by SEM. The composite beads prepared by 30 wt% Cu-BDC particles showed approximately high surface area with micro and meso cavities. Batch adsorption experiments were carried out to explore the adsorption performance of Tetracycline (TC) antibiotic. Results showed that maximum adsorption efficiency of TC was attained at pH 7 using SA/CMC/Cu-BDC composite beads with 30 wt% loading of Cu-BDC powder. The effects of two biopolymeric composite compared with one biopolymeric composites was explored; results showed that SA/CMC/Cu-BDC 30 wt% have higher maximum adsorption capacity (180.5 mg g−1) compared to the SA/Cu-BDC 30 wt% (127 mg g−1). The isotherm equilibrium and kinetic data for TC adsorption onto SA/CMC/Cu-BDC followed Langmuir isotherm model and pseudo-second-order kinetic model, respectively. Thermodynamical parameters revealed that TC adsorption is spontaneous with endothermic nature. The hydrogen bonding, electrostatic and π − π interactions have substantial roles during the adsorption of TC onto SA/CMC/Cu-BDC composite beads

Adsorption, oxidation, kinetic and thermodynamic studies of methyl orange by magnetic Fe3O4 NPs and their chitosan/alginate nanocomposites

ABSTRACT Magnetic iron oxide (Fe3O4) nanoparticles, iron oxide chitosan (Fe3O4-CS) and iron oxide alginate (Fe3O4-AT) nanocomposite beads were synthesised using green synthesis method. They were used as both adsorbents for the adsorption of methyl orange (MO) dye from the wastewater and heterogeneous catalysts for the catalytic wet peroxidation (CWPO) of MO. While the dye removal was successfully performed with Fe3O4NPs, Fe3O4-CS and Fe3O4-AT in both adsorption studies and CWPO, the highest removal efficiency (99%) in the shortest time (8 min for adsorption, 20 min for CPWO) was obtained with Fe3O4-CS for MO removal. The adsorption experiments were performed with the batch techniques at different contact time, pH, initial dye concentration, temperature, amount of adsorbent and foreign ion effect parameters by Fe3O4-CS adsorbent. The equilibrium was quickly reached after 30 min at pH 3 and 298 K. Fitting equilibrium data to Langmuir, Temkin and Freundlich isotherms showed that Langmuir model was more suitable to describe MO adsorption with a maximum monolayer adsorption capacity of 132 mg/g at 298 K. The Experimental data were analysed using intra particle diffusion, pseudo-first-order and pseudo-second-order kinetic models and it was found that the adsorption kinetics followed a pseudo-second-order equation. Based on thermodynamic studies, adsorption process occurred as spontaneous and exothermic. The effects of the amount of catalyst, pH, temperature and H2O2 concentration were investigated to determine their catalytic activities for the decomposition of MO with CWPO technique. The reusability of Fe3O4-CS for both adsorption and CWPO techniques for MO removal was performed, and the adsorption and oxidation efficiency was found to be 97%. Moreover, the reaction kinetics was also investigated and the oxidation reaction was in good agreement with the pseudo-first order kinetic model. The activation energy (Ea) of the reaction was found to be 10.72 kJ/mol.

Adsorptive removal of fluoroquinolone antibiotics using green synthesized and highly efficient Fe clay cellulose-acrylamide beads

Environmentally sustainable clay polymeric nanocomposite hydrogel beads based on carboxymethyl cellulose (CMC), acrylamide (AM), and Fe clay were developed by an ionotropic gelation technique and studied as an efficient adsorbent for fluoroquinolone antibiotics. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Thermo gravimetric analysis (TGA), X-ray diffraction (XRD), swelling measurement, and point of zero charge (pHPZC) were used to define the chemical structure and surface morphology of the prepared nanocomposite hydrogel beads. A series of batch adsorption experiments were used to optimize various parameters affecting the removal of Cipro and Levo. At the optimized condition of solution pH (5), initial antibiotic concentration (10 mg/mL), incubation temperature (35 °C), adsorbent dosage (1500 mg/L), and bead weight (15 g/L), the pollutant removal was more than 92% for Cipro and 93% for Levo. For determining Cipro and Levo adsorption on newly synthesized nanocomposite, isotherm, kinetic, and thermodynamic characteristics were evaluated. The Langmuir model well-represented equilibrium data from adsorption and the pseudo-second-order model clearly describes kinetics data. The maximum adsorption capacity obtained for Cipro and Levo was 57.84 mg/g, and 38.01 mg/g respectively. The reusability study revealed that the Cipro and Levo removal efficiency was above 85% for Cipro and 90% for Levo up to the fifth cycle, and validation with the real water samples confirmed above 70% Cipro and Levo removal. The residual toxicity of treated effluent against freshwater Chlorella sp . was significantly lower (>80%) compared to the untreated one, indicating that the process effectively reduced the environmental toxicity of the pollutants. • Novel Fe clay-CA beads was prepared for efficient removal of fluoroquinolone antibiotics. • Green synthesized Fe clay-CA beads shows good thermal stability with cost effectiveness and environmentally sustainable. • The adsorption process depends on pH, temperature, adsorbent weights and dosage and the initial pollutant concentration. • High adsorption capacity of Cipro and Levo was obtained on Fe clay-CA beads.

Removal of naproxen and diclofenac using magnetic nanoparticles/nanocomposites

Magnetic iron oxide and iron/copper nanoparticles were synthesized using Lathyrus brachypterus extract, and then magnetic Fe3O4–CS, Fe3O4–AT, Fe/Cu–CS and Fe/Cu–AT nanocomposite beads were synthesized using chitosan and alginate natural polymers. They were used for both adsorption and heterogeneous catalysts for the catalytic wet peroxidation (CWPO) of naproxen (NPX), diclofenac (DCF) and NPX + DCF drugs which are important micro-organic pollutants, separately and together (NPX + DCF) from aqueous media. In adsorption studies, the drugs were adsorbed very quickly in the first minutes and then, desorbed in between 8 and 10 min. In competitive adsorption, the adsorbents showed selective properties for DCF and NPX. In CWPO technique, drug removal was achieved in 9 min with a conversion capacity of 92% for DCF with Fe/Cu–CS and 84% for NPX with Fe/Cu–AT optimum experimental conditions, such as pH 5, 30% of H2O2, 100 mg catalyst and 298 K. Based on reusability of the catalysts, it was seen that there was a slight decrease in the removal efficiencies in the third cycle and the stable and active structure of the catalyst was preserved to the desired extent. Furthermore, the oxidation reaction was in good agreement with the pseudo-first-order kinetic model.

Structure-property relationships of Kaolin-nanocomposite beads decorated with tertiary amines: Influence of shape on network elasticity and multi-responsivity

Aluminosilicate mineral Kaolin-loaded nanocomposite beads containing cationic 2-(dimethylamino)ethyl methacrylate (DMAEMA) and thermoresponsive N-isopropylacrylamide (NIPA) have been successfully synthesized by combined method of dropwise freezing into cryogenic liquid and sedimentation cryogelation. Hertzian elasticity, thermal stability, and responsive-swelling properties were investigated. The nanocomposite gels exhibited better mechanical properties and thermal stability than neat copolymer gels. The stress and displacement distribution on surface of Kaolin-loaded nanocomposite beads were evaluated with classical Hertz theory, and the results were compared with the results obtained from Rubber elasticity theory. The scaling relationship for contact stress and surface displacement was obtained assuming Hertz's small contact area, and the compression force was scaled with displacement with an exponent of 1.34 ± 0.08. The elastic properties directly attributed to effective potential showed that Hertz potential is valid for small deformations and the elastic modulus decreased with the swollen bead diameter. Addition of Kaolin and NIPA to PDMAEMA-based network has opposite effect on the mechanical properties. The elastic modulus increased, but the swelling ratio decreased with addition of Kaolin. The opposite behavior was observed when NIPA was added, the swelling increased and the mechanical properties weakened. All gels showed significant temperature sensitivity as a result of combination of PDMAEMA and PNIPA, while the swelling was higher at acidic pH than alkaline pH. An overshooting effect attributed to the dynamic conformational changes of tertiary amine of DMAEMA was observed during swelling in pH 3.6. The increase in network density of nanocomposite gel with addition of Kaolin leads to slower relaxation of molecules, and water absorption tends to become relaxation-controlled. An increase in diffusion exponent is observed as diffusion changes from Fickian to non-Fickian. Influence of single salts; NaCl, KCl and K2CO3 on swelling of nanocomposites was investigated. The swelling of Kaolin-loaded nanocomposites decreased with increasing ionic strength, and a “salting-out” effect was observed. The use of naturally occurring nanoscale particles in such structural material design is an important method for biomedical applications and separation technology.

Statistical physics modeling and evaluation of adsorption properties of chitosan-zinc oxide nanocomposites for the removal of an anionic dye

The development of rapid methods to synthesize cost-effective adsorbents for the dye removal is an emerging and relevant topic in the field of wastewater purification. This study focuses on the preparation of zinc-oxide nanoparticles (NPs) impregnated chitosan (CS@ZnO) nanocomposite beads via mechanical stirring (MS) and microwave-assisted (MA) routes. The beads were characterized and utilized for the removal of Eriochrome Black-T (EBT) dye. Results showed that the CS@ZnO-MA beads provided the best adsorption capacities for EBT removal (40.9 ± 0.83 mg g−1) at pH 3.5. The best composite (CS@ZnO-MA) can be regenerated 5 times without significantly affecting its adsorption properties and can remove 71 % of EBT dye from a multi-pollutant solution. The novelty of this study relies on the facile preparation and impregnation of the biopolymer with metal-oxide NPs, which render high adsorption capacity, mechanical strength and high specific surface area of the CS to contribute in the removal of dye molecules from textile wastewater. An enhanced statistical physics model revealed that the adsorption mechanism of EBT dye molecules on these composites was multimolecular. The study indicates an effective synthesis route that can be implemented to prepare new adsorbents using CS at a large-scale for water treatment.

Bio-sorbent alginate/citric acid-sawdust/Fe3O4 nanocomposite beads for highly efficient removal of malachite green from water

Sawdust is a by-product of wood-related industries with striking features for pollutant uptake. For the first time in the current study, sustainable magnetic alginate composite beads containing citric acid-modified sawdust (CA-sawdust) as a bio-waste and Fe3O4 nanoparticles were designed. This novel eco-friendly composite (Alginate/CA-sawdust/Fe3O4 beads) was successfully applied to remove cationic malachite green (MG). Easy separation under a magnetic field and reusability could be mentioned as two significant properties of this bio-sorbent. The removal percentage of MG using alginate/CA-sawdust/Fe3O4 beads was calculated to be 90–95 %. This process was well-described with Langmuir isotherm and nonlinear pseudo-first-order kinetic models. Moreover, both film and intraparticle diffusion models were found to be probable removal mechanisms.

Synthesis of Alginate/Hydroxyapatite Beads for Acetaminophen Delivery

Conventional drug delivery systems usually involve the intake of multiple drugs, which could amplify the risk of overdosing. Acetaminophen is a widely used pain relief substance that is prone to accidental overdosing. Hence, a controlled drug delivery system is needed to ensure its efficacy. A nanocomposite hydroxyapatite/alginate system that was used as a drug carrier for acetaminophen was synthesized through the sol-gel method, and the mechanism underlying its controlled drug delivery was investigated. Spherical nanocomposite bead samples were synthesized by incorporating 5 wt%, 10 wt%, and 15 wt% hydroxyapatite into mixtures containing alginate. The mixtures were then dropped into calcium chloride solution. The phase purity of the hydroxyapatite sample was confirmed through X-ray diffraction, and the functional groups that confirmed the presence of alginate and hydroxyapatite in the nanocomposite samples were analyzed by using Fourier transform infrared spectroscopy. The release of acetaminophen can be controlled for 48 h, and the Korsmeyer–Peppas kinetics model showed the best correlation for all samples. The kinetics of Al/HAp5, Al/HAp10, and Al/HAp15 were governed by quasi-Fickian diffusion with the n values of 0.199, 0.238, and 0.225, respectively. The composite beads show potential for application as a controlled drug delivery vehicle.

Low-cost biosorbent hybrid hydrogels for paraquat remediation of water

The excessive and indiscriminate use of agrochemicals, such as paraquat (PQ), leads to numerous water pollution problems. The adsorption of aqueous contaminants is one of the most effective methodologies for water purification. This study develops nanocomposite biopolymeric hydrogels of chitosan and clay, and examines the biosorption capacity of PQ from aqueous matrices. The main objective of the work is to achieve a biocomposite with great biosorbent characteristics and low cost. The nanocomposite hydrogels were synthesized by simple techniques and characterized by aqueous absorption capacity, differential scanning calorimetry, thermogravimetric analysis, infrared spectroscopy, X-ray diffraction, microscopic and texture techniques, and surface charge analysis. Besides, their performance in the removal of PQ from aqueous systems was studied in discontinuous tests under different conditions. The results showed maximum adsorption capacities of 0.06, 0.98, 0.94 and 0.99 mg·g−1 for CS, CS/DDA, CS/Bent and CS/LVF beads, respectively. The results showed that the presence of clay is essential for PQ sorption to occur. Thermodynamic, kinetic, and isothermal studies of the nanocomposite beads indicated that biosorption occurred spontaneously and that it has the participation of exothermic physisorption and chemisorption processes, corresponding mainly to the pseudo-second-order kinetic model, and to the Langmuir and Freundlich isothermal models. The CS hydrogel showed a non-spontaneous sorption process associated with the physisorption of PQ on the beads. The tests showed hopeful results for the utilization of the developed nanocomposite hydrogels as PQ biosorbents, with novel properties and low-cost characteristics, which are a sustainable and promising solution for the generation of pollutant-free water.

Studies on photocatalytic removal of antibiotics, ciprofloxacin and sulfamethoxazole, by Fe3O4-ZnO-Chitosan/Alginate nanocomposite in aqueous systems

An ultraviolet-light-induced antibiotic degradation system based on nano-ZnO and Fe3O4 and chitosan/alginate nanocomposite bead assembly has been developed using a facile green-synthesis approach. In this study Camellia sinensis extract was used as reducing agent to facilitate the formation of the nanoparticles. The Fe3O4-ZnO-CS/SA nanocomposite was employed to degrade ciprofloxacin (CIP) and sulfamethoxazole (SMX) under UV-C light irradiation, and 94.77% and 93.31% degradation was achieved respectively within 180 min with the optimized conditions [pH of 4.0, antibiotic concentration of 10 mg/L, and Fe3O4-ZnO-CS/SA nanocomposite weight of 10 g and 15 g for CIP and SMX respectively]. For both the antibiotics, the pseudo-first-order model fitted well with the reaction kinetics data, while the Langmuir isotherm model showed a better fit compared to the Freundlich and Temkin models. Analyzing various characterization data reaction mechanism for CIP and SMX degradation was proposed. In addition, possible degradation pathways of CIP and SMX were proposed based on the intermediates detected by HR-LCMS analysis. Furthermore, the trapping experiments showed that superoxide (1O2) and hydroxyl (OH) radicals play major role in the photodegradation of CIP and SMX. The effects of ionic strength, natural organics and various natural water systems on degradation efficacy was investigated. The degraded products were found to show less toxicity to a model organism, a fresh water alga, compared to the parent compounds. This work provides a simple strategy to integrate CS/SA with nano-ZnO and Fe3O4 to construct effective nanocomposite photocatalyst for the degradation of different classes of antibiotics.

Mechanistic insight into impact of clay on compressive elasticity of poly(N-alkyl acrylamide)/Laponite-based nanocomposite cryo-beads

Relationship between formation pathway and Hertzian elasticity of poly(N-isopropylacrylamide-co‑sodium acrylate)/Laponite® XLG, P(NIPA-NaA)/LAP, based nanocomposite cryo-beads was evaluated. Millimeter-sized nanocomposite cryo-beads were prepared by combination of dropwise freezing into cryogenic liquid (DFLC) method with sedimentation cryogelation method. pH-sensitive 3D-templete was formed by conducting free-radical crosslinking cryopolymerization of NIPA and NaA in the presence of synthetic hectorite Laponite® XLG as inorganic crosslinker and N,N′-methylenebis(acrylamide) as chemical crosslinker. The effects of network template, ionic comonomer, inorganic clay incorporation, pH- and ionic strength of swelling medium on the swelling and elasticity were evaluated as a function of bead size. The deformability of swollen cryo-beads was investigated using Hertzian elasticity. The crosslink density and Hertz modulus of nanocomposite beads vary with the droplet size and the polymer spheres with low crosslink density tend to absorb more water. In DFLC method, the desired sphere size and swelling can be adjusted by selecting the needle size used for dripping. The swelling degree increased significantly as the size of nanocomposite cryo-beads increased. At a fixed swelling ratio, the cylindrical nanocomposite cryogels exhibited greater elastic moduli and crosslink density than that of spherical gels. Correlation of elastic modulus of cryo-beads with swelling and cross-linked polymer concentration predicted a higher scaling exponent than the classical estimate for swelling in good solvents. It was investigated how the presence of 30 mol% pH-sensitive anionic comonomer NaA in the structure of all nanocomposite gels affects their pH-dependent swelling behavior. At pH < 5.7, the gels exhibited a lower swelling ratio, whereas at pH > 6.6 they tended to swell and followed second-order swelling kinetics by Fickian diffusion. When pH of swelling medium was alternately changed, all gels exhibited a pH-switch and swelling rate was two times higher than shrinkage rate. By investigating the effect of KCl, NaCl and K2CO3 on the swelling of cryobeads, it was determined how the salt cation changes the electrostatic repulsion between network charges. Nanocomposite cryo-beads showed fast pH-responsiveness and immediately reabsorbed the water they lost due to pH change, therefore, they can be designed as drug release carriers by pH-switching modulation.

Development of hybrid green nanocomposite polymeric beads doped with nano sulfated zirconia for effective removal of Cefotaxime antibiotic from aqueous solution

Adsorption efficiency of Cefotaxime by novel nanocomposites beads composed of iota carrageenan (IC), sulfonated poly vinyl alcohol (SPVA) and nano sulfated zirconia (SZrO2) was evaluated in this study. SZrO2 was synthesized from solvent-free and easy calcination technique then embedded with 1–2.5 wt.% into the polymeric matrix. A batch adsorption experiment was carried out to investigate the effects of dosage, pH, beginning concentration, and time on Cefotaxime antibiotic adsorption. The ideal conditions to achieve complete removal are 88.97 mg L−1 initial cefotaxime concentration at time 3.58 h with 11.68 mg of beads composite with 2.5 wt.% of SZrO2. The pseudo second order kinetics model better illustrated the adsorption of cefotaxime on nanocomposite beads, and the maximum adsorption capacity are 659 mg g−1 for the composite with 2.5 wt.% of SZrO2. The mechanism of adsorption process depend mainly on the interactions between the different functional groups of SPVA, IC and SZrO2. The nanocomposites beads also exhibit excellent reproducibility after ten adsorption cycles. This type of nanocomposites beads can be easily separated from water without leaving any residue, verifying this novel nanocomposite beads has strong potential in water treatment for the antibiotic contaminant removal.

Study of Isotherm and Kinetics for Remediation of Congo Red Using Nanocomposite Bead

Cellulose-based nanocomposite (FeCNB) has been synthesized via sol-gel conversion for adsorptive remediation of Congo red, a carcinogenic and mutagenic azo dye, from water. The bead was characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX) and transmission electron microscopy (TEM). The effect of adsorbent dose, pH, contact time, shaking speed, initial dye concentration and temperature was carried out in a batch adsorption study. The maximum removal of Congo red was found at pH 6.0, corresponding to the adsorbent dose of 1.0 gdm-3 and 90 min of contact time. The experimental data were analyzed using different isotherm and kinetic models. The data was fitted best to Langmuir isotherm model and pseudo-second-order kinetic model. The maximum adsorption capacity evaluated from Langmuir isotherm is 3.52 mgg-1 at 303 K. Thermodynamic study was carried out to evaluate the changes in Gibbs free energy (ΔG0 ), enthalpy (ΔH0 ) and entropy (ΔS0 ) of the dye-adsorbent interaction. The negative ΔG0 values at all temperatures suggested the spontaneous nature; the positive ΔH0 value indicated the endothermic nature and the positive ΔS0 indicated the increased randomness of the adsorption process. Desorption study found 0.1 (M) NaOH as the most suitable eluting agent for dye-loaded adsorbent. The adsorbent can be used up to five successive cycles of adsorption-desorption.

Efficient adsorption of heavy metals from wastewater on nanocomposite beads prepared by chitosan and paper sludge

Chitosan was commonly used with inorganic salt and organic compounds to prepare adsorption material for water treatment. Different materials were mixed for the preparation, leading to a high cost for water treatment. Sludge from papermaking has abundant fiber and inorganic salt, which can reduce the addition of raw materials in preparing the adsorption material and thus lower the cost. This work used recycled industrial paper sludge to prepare adsorption material to remove heavy metals from wastewater. The adsorption properties of the prepared sludge-chitosan material for Cu2+ and Cr3+ in wastewater were investigated. The impacts of adsorption time, pH, and initial concentrations of Cu2+ and Cr3+ on adsorption amount were studied and optimized. The saturated adsorption capacity of sludge-chitosan material for Cu2+ and Cr3+ can reach 114.6 and 110.3 mg/g. The adsorption kinetics satisfied the pseudo-second-order model, indicating two modes, physical diffusion, and chem-sorption, in the heavy metal adsorption by the sludge-chitosan materials. Physical distribution has little Effect on chemical adsorption. The materials can be applied to treating Cu2+ and Cr3+ containing wastewater with the proposed cheap and readily available sludge-chitosan material. The results confirmed that sludge-chitosan material possessed good regeneration performance and was an ideal adsorbent.

Multi-ionic interaction with magnesium doped hydroxyapatite-zeolite nanocomposite porous polyacrylonitrile polymer bead in aqueous solution and spiked groundwater

Removal of multi-ionic contaminants from water resources has been a major challenge faced during the treatment of water for drinking and industrial applications. In the present study, varying composition of magnesium doped hydroxyapatite (Mg-HAp) and zeolite nanocomposite embedded porous polymeric beads were synthesized using solvent displacement method and its sorption efficiency towards multi-ion contaminant (such as Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, Tl, Th, U, V and Zn) was investigated in aqueous solution and spiked groundwater. The prepared beads were characterized using suitable techniques like high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) equation. The surface area and pore radius of the beads varied from 6.996 to 66.469 m2/g and 1.698–3.960 nm respectively according to the composition of the bead. The control bead without nanocomposite showed maximum surface area. Multi-ion adsorptions onto beads were confirmed using an inductively coupled plasma-optical emission spectrophotometer (ICP-OES) and X-ray photoelectron spectrophotometer (XPS). The sorption efficiency was high at pH 5 owing to its anionic surface charge leading to an increase in affinity towards the cations. For validating field application, selected high performance beads were tested in multi-ion spiked groundwater. The results indicated that the Mg-HAp nanocomposite bead dominate all the other bead compositions with more than 90% removal efficiency for most of the multi-ion contaminants. The feasible adsorption mechanism has been discussed. This adsorption study revealed that the Mg-HAp nanocomposite bead is a promising material that is cost-effective, non-toxic, biodegradable, eco-friendly and highly efficient towards the removal of multi-ionic contaminants from groundwater.

Insights into catalytic reduction of dyes catalyzed by nanocomposite beads Alginate@Fe3O4: Experimental and DFT study on the mechanism of reduction

In the present work, a facile pathway was developed to prepare magnetic alginate nanocomposite beads (M@AN). The prepared nanocomposite beads were evaluated as a catalyst for the degradation of methylene blue (MB) and orange G (OG) dyes in a simple and binary system under the presence of a reducing agent NaBH4. The in-situ formed magnetic nanoparticles (Fe3O4-NPs) were identified by visual observance, X-ray diffraction (XRD), UV–Vis DR Spectroscopy (UV–vis DR), Fourier transform infrared (FTIR) spectroscopy and energy dispersive x-ray (EDS). The obtained results revealed the formation of dispersed Fe3O4-NPs inside the beads linked with −COO groups of alginate biopolymer by a bidentate bridging coordination. Owing the presence and well-dispersed Fe3O4 nanoparticles in M@AN surface. The prepared catalyst was more efficient with the cationic MB dye in the simple and binary system. In the simple system, the rate constant was 0.0034 s−1 and 7.416 10−4 s−1 for MB and OG dye, respectively, whereas in the binary system the rate constant was 0.0012 s−1 and 5.096 10−4 s−1 for MB and OG dye, respectively. To have deep insight into the reduction mechanism of MB dye onto M@AN, the density functional theory (DFT) method was used. The results showed that the NaBH4 and MB reagents are firstly diffused onto the surface of the nanocatalyst via hydrogen banding, then, the reduction reaction was carried out by a nucleophilic attack of borohydride ion by hydrogenation on the double bond between carbon and nitrogen in –NC– group of MB which thereafter transformed into –NH–CH– bond. The theoretical results show good agreement with the experimental data, in which the calculated UV–visible spectrum of Leuco–MB product using DFT method shows an electronic transition at 300 nm which is a close value to the experimental.