Appraisal of the adsorption potential of novel modified gellan gum nanocomposite for the confiscation of methylene blue and malachite green.

In the present investigation a novel, environmentally affable and economical, modified gellan gum nanocomposite (MAA-g-GG/Ppy/MMT) was fabricated via free-radical polymerization for the liquid-phase mitigation of Methylene blue (MB) and Malachite green (MG) dyes. The innovation of this work is substantiated by the intentional combination of diverse materials, the strategic incorporation of polypyrrole for enhanced adsorption, and the thoughtful addition of MMT as a nanofiller to address mechanical strength and improve adsorption capacity. The physico-chemical facets of MAA-g-GG/Ppy/MMT and its interaction with the dye molecules were elucidated using FT-IR, SEM-EDX, BET, TEM, and XRD techniques. The optimum conditions for the sorption of MB and MG were deemed to be dosage (1.2 g/L for both dyes), contact time (50 min for both dyes), initial MG/MB concentration (MB = 40 mg/L & MG = 30 mg/L), and pH (MB = 10 & MG = 7). The Freundlich isotherm was identified as the most suitable model, as evidenced by the highest R2 value (∼0.999), indicating multilayer adsorption. The pseudo second-order model appraised the kinetic data. Thermodynamic findings revealed the adsorption process to be spontaneous, viable and exothermic which was ascertained by negative ∆H⸰ values (-22.8 kJ/mol for MB and -18.3 kJ/mol for MG). The substantial Langmuir adsorption capacity (Qm: MG =185.185; MB = 344.827) can be ascribed to the reason for strong interactions between MAA-g-GG/Ppy/MMT and dyes. The high reliability of MAA-g-GG/Ppy/MMT was determined by the regeneration studies that worked up to four cycles for both dyes. The real water (distilled water, tap water, and river water) samples spiked with MG/MB demonstrated a substantial uptake of dyes (>85 %) and the marginal influence of ionic strength on the adsorptive potential of MAA-g-GG/Ppy/MMT validated its efficacy for the decontamination of real effluents. The forces of attraction between the dyes and MAA-g-GG/Ppy/MMT included van der Waals, electrostatic forces of attraction, and π-π interaction. This green, economical, and viable MAA-g-GG/Ppy/MMT will prove to be an efficient adsorbent for the decontamination process of sequestration of dyes to achieve a sustainable environment.

Comparative Study of ZnO-and-TiO2-Nanoparticles-Functionalized Polyvinyl Alcohol/Chitosan Bionanocomposites for Multifunctional Biomedical Applications.

This study aimed to synthesize chitosan/polyvinyl alcohol (CS/PVA)-based zinc oxide (ZnO) and titanium dioxide (TiO2) hybrid bionanocomposites (BNCs) and observe their comparative accomplishment against the skin cancer cell line, A431, and antioxidant potential. CS was blended with PVA to form polymeric films reinforced with the immobilization of ZnO and TiO2 nanoparticles (NPs), separately. The optimization of the BNCs was done via physicochemical studies, viz. moisture content, swelling ratio, and contact angle measurements. The free radical scavenging activity was observed for 1,1-diphenyl-2-picryl-hydrazyl, and the antibacterial assay against the Escherichia coli strain showed a higher zone of inhibition. Furthermore, the anticancer activity of the synthesized BNCs was revealed against the skin cancer cell line A431 under varying concentrations of 50, 100, 150, 200, and 300 µg/mL. The anticancer study revealed a high percent of cancerous cell inhibition (70%) in ZnO BNCs as compared to (61%) TiO2 BNCs in a dose-dependent manner.

Synergistic effect of silver NPs immobilized on Fe3O4@L-proline magnetic nanocomposite toward the photocatalytic degradation of Victoria blue and reduction of organic pollutants.

The surface of magnetite (Fe3O4) nanoparticles was subject to modification through the incorporation of L-proline (LP) by simple co-precipitation method in which silver nanoparticles were deposited by in situ method, thereby yielding the Fe3O4@LP-Ag nanocatalyst. The fabricated nanocatalyst was characterized using an array of techniques including Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), Brunauer-Emmett-Teller (BET), and UV-Vis spectroscopy. The results evince that the immobilization of LP on the Fe3O4 magnetic support facilitated the dispersion and stabilization of Ag NPs. The SPION@LP-Ag nanophotocatalyst exhibited exceptional catalytic efficiency facilitating the reduction of MO, MB, p-NP, p-NA, NB, and CR in the presence of NaBH4. The rate constants obtained from the pseudo-first-order equation were 0.78, 0.41, 0.34, 0.27, 0.45, 0.44, and 0.34 min-1 for CR, p-NP, NB, MB, MO, and p-NA, respectively. Additionally, the Langmuir-Hinshelwood model was deemed the most probable mechanism for catalytic reduction. The novelty of this study lies in the use of L-proline immobilized on Fe3O4 MNPs as a stabilizing agent for the in-situ deposition of silver nanoparticles, resulting in the synthesis of Fe3O4@LP-Ag nanocatalyst. This nanocatalyst exhibits high catalytic efficacy for the reduction of multiple organic pollutants and azo dyes, which can be attributed to the synergistic effects between the magnetic support and the catalytic activity of the silver nanoparticles. The easy recyclability and low cost of the Fe3O4@LP-Ag nanocatalyst further enhance its potential application in environmental remediation.

A review on remediation of dye adulterated system by ecologically innocuous "biopolymers/natural gums-based composites".

The mitigation of wastewater exploiting biopolymers/natural gums-based composites is an appealing research theme in today's scenario. The following review presents a comprehensive description of the polysaccharides derived from biopolymers (chitosan, collagen, cellulose, starch, pectin, lignin, and alginate) and natural gums (guar, gellan, carrageenan, karaya, moringa oliefera, tragacanth, and xanthan gum). These biopolymers/natural gums-based composites depicted excellent surface functionality, non-toxicity, economic and environmental viability, which corroborated them as potential candidates in the decontamination process. The presence of -OH, -COOH, and -NH functional groups in their backbone rendered them tailorable for modification/functionalization, and anchor an array of pollutants via electrostatic interaction, hydrogen bonding, and Van der Waals forces. Further, due to these functional moieties, these bio-based composites revealed an excellent adsorption capacity than conventional adsorbents. This review provides an overview of the classification of biopolymers/natural gums based on their origin, different ways of their modification, and the remediation of dye-contaminated aqueous environments employing diverse bio-based adsorbents. The isotherm, kinetic modelling along with thermodynamics of the adsorption process is discussed. Additionally, the reusable efficacy of these bio-adsorbents is reviewed.

A comprehensive review on bio-mimicked multimolecular frameworks and supramolecules as scaffolds for enzyme immobilization.

Immobilization depicts a propitious route to optimize the catalytic performances, efficient recovery, minimizing autocatalysis, and also augment the stabilities of enzymes, particularly in unnatural environments. In this opinion, supramolecules and multimolecular frameworks have captivated immense attention to achieve profound controllable interactions between enzyme molecules and well-defined natural or synthetic architectures to yield protein bioconjugates with high accessibility for substrate binding and enhanced enantioselectivities. This scholastic review emphasizes the possibilities of associating multimolecular complexes with biological entities via several types of interactions, namely covalent interactions, host-guest complexation, π - π ${\rm{\pi }}-{\rm{\pi }}$ interactions, intra/inter hydrogen bondings, electrostatic interactions, and so forth offers remarkable applications for the modulations of enzymes. The potential synergies between artificial supramolecular structures and biological systems are the primary concern of this pedagogical review. The majority of the research primarily focused on the dynamic biomolecule-responsive supramolecular assemblages and multimolecular architectures as ideal platforms for the recognition and modulation of proteins and cells. Embracing sustainable green demeanors of enzyme immobilizations in a quest to reinforce site-selectivity, catalytic efficiency, and structural integrality of enzymes are the contemporary requirements of the biotechnological sectors that instigate the development of novel biocatalytic systems.

Development of highly efficient magnetically recyclable Cu2+/Cu0 nano-photocatalyst and its enhanced catalytic performance for the degradation of organic contaminations.

This work reports the successful functionalization of l-proline on the surface of superparamagnetic iron oxide nanoparticles (SPION) synthesized via a simple, cost-effective hydrothermal method. Moreover, the chemical attachment of Cu2+/Cu0 nanoparticles on the surface of SPION@l-proline was done by an in-situ deposition method. The developed nano-photocatalyst was characterized in detail by XRD, FT-IR, XPS, FE-SEM, TEM, EDX, BET, TGA, and VSM. XRD of SPION@l-proline-Cu reveals peaks of both SPION and copper nanoparticles which confirms the formation of nanophotocatalyst. TGA demonstrates a major weight loss between 250 and 310 °C due to l-proline which ensures the successful immobilization of SPION on the surface of l-proline. The band energy at 932 eV suggests a complete reduction of Cu2+ ion to Cu0 metal on the surface of SPION@l-proline nanocomposite as confirmed by the XPS technique. Under UV light irradiation, the photocatalytic reduction performance of the developed Cu2+ metal ion-based and Cu0 nanoparticle-based magnetic nano-photocatalysts was demonstrated and compared for the first time for the photocatalytic reduction of 4-NP, 4-NA, NB, MO, MB, and CR. The results show that Cu0-based magnetic nanophotocatalyst has slightly enhanced catalytic activity. Furthermore, solar-driven photocatalytic degradation of CR azo dye by synthesized nano-photocatalyst was also investigated, with a 95 % degradation efficiency in just 40 min. The developed magnetic nano-photocatalyst can easily be separated by using an external magnet due to the superparamagnetic nature of core material (SPION) at room temperature as confirmed from VSM and can be reused for multiple cycles without losing considerable catalytic activity. Because of its high photocatalytic efficiency, cost-effectiveness, good magnetic separation performance, non-toxicity, and strong thermal and chemical stabilities, Cu2+/Cu0-based magnetic nano-photocatalyst has potential application in wastewater treatment.

Zinc oxide nanoparticles-impregnated chitosan surfaces for covalent immobilization of trypsin: Stability & kinetic studies.

Trypsin (Try, EC. 3.4.21.4) was effectively immobilized on the surface of glutaraldehyde(GA)-activated ZnO/Chitosan nanocomposite through covalent attachment via Schiff-base linkages. Size, structure, surface morphology, & percentage elemental composition of the prepared ZnO nanoparticles and chitosan-coated ZnO nanocomposite were studied by UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction analysis (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and Energy-Dispersive X-Ray Microanalysis (EDAX) techniques. Optimal immobilization conditions (incubation time (16 h), enzyme concentration (1.8 mg/ml), and pH (7.8)) were investigated to obtain the maximum expressed activity of the immobilized trypsin. Immobilized & solubilized trypsin exhibited the optimum catalytic activity at pH 8.5, 60 °C, and pH 7.8, 45 °C respectively. Kinetic parameters (Km, Vmax) of immobilized (27.12 µM, 8.82 µM/min) & free trypsin (25.76 µM, 4.16 µM/min) were determined, indicating that efficiency of trypsin improves after immobilization. Immobilized trypsin preserved 67% of initial activity at 50 °C during 2 h of incubation & sustained nearly 50% of catalytic activity until the 9th repeated cycle of utilization. Moreover, immobilized trypsin retained 50% of enzymatic activity after 90 days of storage at 4 °C. Hence, the current findings suggest that ZnO/Chitosan-GA-Trypsin would be a promising biocatalyst for large-scale biotechnological applications.

Critical review on adsorptive removal of antibiotics: Present situation, challenges and future perspective.

This review gives a proper dedicated understanding of the contamination level, sources, and biological dangers related with different classes of antibiotics in consumable water. The literature on the adsorption of antibiotics is relatively uncommon and developments are still under progression, especially for adsorbents other than activated carbon. Also, adsorption technique has already been applied vastly for water treatment. Notwithstanding significant progressions, designed natural wastewater treatment frameworks are just bearably effective (48-77%) in the expulsion of antibiotics. Hence, the compilation of available literature especially for antibiotic adsorption was much needed. Moreover, the conventional adsorbents have some limitations of their own. In this study, the main focus was laid on unconventional adsorbents such as Biochar, Biopolymers, Carbon Nanotubes, Clays, Metal-Organic Frameworks, Microalgae and some miscellaneous adsorbents. The mechanism of adsorption by the unconventional adsorbents includes electrostatic interactions, π-π bonding, weak Van der Waal forces, H-bonding and surface complexation, which was similar to that of conventional adsorbents and hence these unconventional adsorbents can easily replace the costlier conventional adsorbents with even better adsorption efficiency. This paper also briefly discussed the thermodynamics, adsorption equilibrium; isotherm and kinetics of adsorption. This review paper seizes the critical advances of adsorption phenomenon at various interfaces and lays the foundation for current scenario associated with further progress. Besides, this study would help in understanding the antibiotic adsorption, cost estimation and future goals that will attract the young the researchers of this field.

Execution and viable applications of face shield "a safeguard" against viral infections of cross-protection studies: A comprehensive review.

Face shield are the unmistakable plastic gatekeepers secures eyes and face, simpler to wear and a group of specialists state face shields may supplant masks as an increasingly agreeable and progressively successful obstacle to COVID-19. Face shields are useful in stopping respiratory droplets from speading from the wearer to others. The droplets, which come into contact with the shield, are quickly spread over a large area, both transversely and vertically, over the shield, but with a shrinking concentration of droplets, as opposed to face masks, which appear to slide under the nose of the wearer or, worse, collapse entirely off the shield. Hence, a face- shield can be considered as personal protective equipment (PPE), which is a first line of resistance, utilized by the clinicians and forefront health workers for protection against the infectious body fluid and aerosols. Face-shields are mainly fabricated using polycarbonate material, because of their excellent optical transparency in UVA-visible-IR spectrum and mechanical properties. The goal of this article is to provide researchers working in the same area, as well as health and industrial staff, with a detailed analysis of the usage of face shields against bioaerosols and the need for personal security. The reviews main focus on the background of the face shield, provide assistance in the selection, its design and structure, applications, advantages and disadvantages. Lastly, people's view about the usage of face shield as it becomes an essential part of human beings like an accomplice during this current pandemic situation.

A comprehensive review on incredible renewable carriers as promising platforms for enzyme immobilization & thereof strategies.

Enzymes are the highly versatile bio-catalysts having the potential for being employed in biotechnological and industrial sectors to catalyze biosynthetic reactions over a commercial point of view. Immobilization of enzymes has improved catalytic properties, retention activities, thermal and storage stabilities as well as reusabilities of enzymes in synthetic environments that have enthralled significant attention over the past few years. Dreadful efforts have been emphasized on the renewable and synthetic supports/composite materials to reserve their inherent characteristics such as biocompatibility, non-toxicity, accessibility of numerous reactive sites for profitable immobilization of biological molecules that often serve diverse applications in the pharmaceutical, environmental, and energy sectors. Supports should be endowed with unique physicochemical properties including high specific surface area, hydrophobicity, hydrophilicity, enantioselectivities, multivalent functionalization which professed them as competent carriers for enzyme immobilization. Organic, inorganic, and nano-based platforms are more potent, stable, highly recovered even after used for continuous catalytic processes, broadly renders the enzymes to get efficiently immobilized to develop an inherent bio-catalytic system that displays higher activities as compared to free-counter parts. This review highlights the recent advances or developments on renewable and synthetic matrices that are utilized for the immobilization of enzymes to deliver emerging applications around the globe.

Morphological and Swelling Potential Evaluation of Moringa oleifera Gum/Poly(vinyl alcohol) Hydrogels as a Superabsorbent.

Synergistic use of superabsorbent hydrogels has vital contribution to the daily life. This work gives an account of a facile approach to synthesize superabsorbent hydrogels based on Moringa oleifera gum and polyvinyl alcohol cross-linked with borax. Fourier transform infrared, X-ray diffraction, and scanning electron microscopy were employed to characterize the structure, crystallinity, and surface morphologies of the samples. The cross-link density, swelling ratio, reswelling, water retention properties, and salt sensitivity of hydrogels were investigated. Reaction parameters for the hydrogel synthesis were optimized on the basis of water absorbency, and the reaction condition of greater water absorbency after 12 h at room temperature was taken as an ideal condition. Optimum conditions were obtained as [poly(vinyl alcohol) PVA] = 10% (w/v) and [borax] = 1.05 × 10-3 mol/L. Under the optimized conditions, the maximum swelling ratio of MOG/PVA hydrogel reached 1163 g/g in deionized water and 290 g/g in 0.9 wt % NaCl solution. Furthermore, all hydrogels exhibited salt sensitivity and excellent water retention capacity under the high temperature state and displayed smart swelling behaviors in physiological saline solutions. The water absorbency, reusability, and salt sensitivity of the hydrogels give these smart polymer wide promising applications.

Correction: Removal of Pb(ii) and Cd(ii) from wastewater using arginine cross-linked chitosan-carboxymethyl cellulose beads as green adsorbent.

[This corrects the article DOI: 10.1039/C9RA00356H.].

Synthesis, Characterization, Kinetics, and Thermodynamics of EDTA-Modified Chitosan-Carboxymethyl Cellulose as Cu(II) Ion Adsorbent.

A new adsorbent derived from the naturally occurring biopolymers, chitosan (CS) and carboxymethyl cellulose (CMC) was prepared by cross-linking them using EDTA. EDTA having high affinity for metal ions can be used to enhance the chelation properties of the adsorbent enormously. The product obtained (chitosan-EDTA-CMC, CSECM) was characterized by different techniques: FTIR, XRD, SEM/EDAX, TGA, and XPS. The parameters for evaluation of the adsorption properties for removal of Cu(II) ions from the aqueous solution were determined using the batch adsorption method by studying the effect of pH, contact time, initial ion concentration, and temperature on adsorption. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models were applied to study the kinetics of the adsorption process, whereas Langmuir, Freundlich, Temkin, and D-R models were applied to evaluate the thermodynamics of the adsorption process. The kinetic adsorption parameters were in best agreement with the pseudo-second-order model, while thermodynamic parameters best fitted to the Langmuir isotherm at different temperatures for adsorption of Cu(II) ions from aqueous solution with a maximum adsorption capacity of 142.95 mg/g at pH 5.5. CSECM showed excellent regeneration capability and recovery of the Cu(II) ion up to five cycles without the loss of the adsorption efficiency, which is the best characteristic to select the appropriate choice of the adsorbent. The adsorbent was also employed in batch experiments to evaluate the adsorption of hardness, producing common metal ions in single and real wastewater solutions.

A review on latest innovations in natural gums based hydrogels: Preparations & applications.

The prospective uses of natural gum polysaccharides in various aspects of food, water, energy, biotechnology, environment and medicine industries, have garnered a great deal of attention recently. Natural gums have gained widespread attention due to their availability, low cost, structural diversity and remarkable properties as 'green' bio-based renewable materials. Natural gums are obtainable as natural polysaccharides from various tree genera possessing exceptional properties, including their renewable, biocompatible, biodegradable, and non-toxic nature and their ability to undergo easy chemical modifications. Hydrogels based on natural gums offer several valuable properties when equated to synthetic origin. The fundamental objective of this review is to compile different strategies for the preparation of hydrogels based on several important commercially available gums (arabic, guar, gellan, ghatti, karaya, kondagogu, konjac, locust bean tamarind, tragacanth, tara and xanthan) for the greener synthesis and stabilization of metal/metal oxide NPs, production of electrospun fibers, water purification, drug delivery, tissue engineering, agriculture and for antimicrobial and biomedical applications.

New method for hydrogel synthesis from diphenylcarbazide chitosan for selective copper removal.

In this work, a simple method was developed for hydrogel preparation from 1,5-Diphenylcarbazide (DPC) and chitosan (CS) through Diazotization reaction of CS as a selective adsorbent (DPCCS) for Cu(II) ions. CS was treated with sodium nitrate and subsequent crosslinking reaction with DPC for the preparation of DPCCS. Different techniques were used for characterization of DPCCS. Various parameters such as, temperature, pH, and concentration of Cu(II) were used for adsorption studies. Kinetics of Cu(II) ion on DPCCS follows the Pseudo second order and equilibrium of adsorption occurs in short time. The equilibrium data was best fitted with the Langmuir isotherm and the maximum adsorption capacity of DPCCS was 185.505 mg g-1. Thermodynamic parameters ΔG°, ΔH° and ΔS° suggested that the adsorption of Cu(II) ion on the surfaces of DPCCS was spontaneous, endothermic and randomness of Cu(II) ion in the solution was enhanced respectively. Regeneration of DPCCS and Cu(II) ion recovery were studied up to five cycles without the lost of the adsorption capacity.

Removal of Pb(ii) and Cd(ii) from wastewater using arginine cross-linked chitosan-carboxymethyl cellulose beads as green adsorbent.

A one pot approach has been explored to synthesize crosslinked beads from chitosan (CS) and carboxymethyl cellulose (CM) using arginine (ag) as a crosslinker. The synthesized beads were characterized by FTIR, SEM, EDX, XRD, TGA and XPS analysis. The results showed that CS and CM were crosslinked successfully and the obtained material (beads) was analyzed for adsorption of Cd(ii) and Pb(ii) by using batch adsorption experiments; parameters such as temperature, contact time, pH and initial ion concentration were studied. Different kinetic and thermodynamic models were used to check the best fit of the adsorption data. The results revealed that the kinetics data of the adsorption of Pb(ii) and Cd(ii) ions shows the best fit with the pseudo second order model whereas the thermodynamics data shows the best fit with the Langmuir isotherm with maximum adsorption capacities of 182.5 mg g-1 and 168.5 mg g-1 for Pb(ii) ions Cd(ii) ions, respectively. For the recovery and the regeneration after the one use of the beads, several adsorption-desorption cycles were carried out to check the reusability and recovery of both the metal ion and the adsorbent without the loss of maximum adsorption efficiency.

Evaluation of the antioxidant, antibacterial and anticancer (lung cancer cell line A549) activity of Punica granatum mediated silver nanoparticles.

This work aimed to synthesize silver nanoparticles via an environmentally benign route, using the aqueous extract of Punica granatum as a precursor as well as a stabilizing and reducing agent. The as-synthesized silver nanoparticles were confirmed using UV-visible spectroscopy with an absorbance peak at 450 nm and were thereafter further confirmed using dynamic light scattering (DLS), High Resolution Transmission Electron Microscopy (HR-TEM) and X-Ray Diffraction (XRD). TEM analysis revealed 6-45 nm and spherically dispersed nanoparticles and XRD showed the crystalline nature of the nanoparticles. The free radical scavenging activity of the nanoparticles for DPPH and intracellular reactive oxidative species (ROS) production were observed using dihydroethidium (DHE) non-fluorescent stain and a CellROX® Deep Red fluorescent probe. Antibacterial assays against the most common Gram negative (Escherichia coli) and Gram positive (Staphylococcus aureus) bacteria showed a higher zone of inhibition against S. aureus. Furthermore, the anti-cancerous activity of the biologically synthesized silver nanoparticles was revealed by the inhibited cell growth of lung cancer A549 cells and no cytotoxicity was observed. This may be due to their ability to arrest the cell cycle at G1 phase. Thus, this work provides a gateway to explore more about the anticancer properties of biogenically synthesized silver nanoparticles and these biologically prepared silver nanoparticles have the potential to be utilized in biomedical science.

Chitosan centered bionanocomposites for medical specialty and curative applications: A review.

The polyfunctional nature of chitosan enables its application not only in polymer technology but also shows their importance in the field of nanotechnology for the fabrication of the wide spectrum of functional nanomaterials in biomedical field. Chitosan is a poly aminosaccharide with appealing structure composed of ß-(1→4)-linked D-glucosamine (deacetylated unit) and N-acetyl-d-glucosamine (acetylated unit). It has various functional groups that enriches for various properties such as antibacterial, mucoadhasive, nontoxic, biodegradable, biocompatible. With the advancement of material technologies, chitosan is being chemically modified into self-assembled nanocomposites for advanced biomedical applications. This review article demonstrate the various schemes for the preparation of chitosan nanocomposites from different functional material, focusing on their application specifically in tissue engineering, drug and gene delivery, wound healing and bioimaging.

Versatile nature of hetero-chitosan based derivatives as biodegradable adsorbent for heavy metal ions; a review.

The polyfunctional chitosan can act as the biological macromolecule ligand not only for the adsorption and the recovery of metal ions from an aqueous media, but also for the fabrication of novel adsorbents which shows selectivity and better adsorption properties. The unmodified chitosan itself, a single cationic polysaccharide, has hydroxyl and amine groups carrying complex properties with the metal ions. In addition, the selectivity of metal ions, the adsorption efficiency and adsorption capacity of the adsorbent can be modified chemically. This review covers the synthetic strategies of chitosan towards the synthesis of hetero-chitosan based adsorbents via chemical modifications in past two decades. It also includes how chemical modification influences the metal adsorption with N, O, S and P containing chitosan derivatives. Hope this review article provides an opportunity for researchers in the future to explore the potential of chitosan as an adsorbent for removal of metal ions from wastewater.

A review on biogenic synthesis of ZnO nanoparticles using plant extracts and microbes: A prospect towards green chemistry.

Nanotechnology is emerging as an important area of research with its tremendous applications in all fields of science, engineering, medicine, pharmacy, etc. It involves the materials and their applications having one dimension in the range of 1-100nm. Generally, various techniques are used for syntheses of nanoparticles (NPs) viz. laser ablation, chemical reduction, milling, sputtering, etc. These conventional techniques e.g. chemical reduction method, in which various hazardous chemicals are used for the synthesis of NPs later become liable for innumerable health risks due to their toxicity and endangering serious concerns for environment, while other approaches are expensive, need high energy for the synthesis of NPs. However, biogenic synthesis method to produce NPs is eco-friendly and free of chemical contaminants for biological applications where purity is of concerns. In biological method, different biological entities such as extract, enzymes or proteins of a natural product are used to reduce and stabilised formation of NPs. The nature of these biological entities also influence the structure, shape, size and morphology of synthesized NPs. In this review, biogenic synthesis of zinc oxide (ZnO) NPs, procedures of syntheses, mechanism of formation and their various applications have been discussed. Various entities such as proteins, enzymes, phytochemicals, etc. available in the natural reductants are responsible for synthesis of ZnO NPs.