Preparation of PVP–PVA–exfoliated graphite cross-linked composite hydrogels for the incorporation of small tin nanoparticles

Effective chromium removal of metal anchored alginate-chitosan binary bio-composites

Water is the most essential resource for the biotic and abiotic components of an ecosystem. Any change in the quality of this water may cause adverse impact on the ecosystem. Hexavalent chromium is one such important pollutant that gets exposed in the water mainly through anthropogenic processes. Adsorption is considered to be an effective, economic and easiest method for remediation of such pollutants. Amongst the innumerable adsorbents available, biopolymers fetch the interest due to its cost effectiveness, efficiency and biocompatibility. But, the mechanical strength and workability of such biopolymers makes it unfit to use as an adsorbent. To improve these drawbacks, synthesis of biopolymeric composites become the need of the hour. So, an attempt was made here to synthesize metal cross-linked binary bio-composites using Alginate and Chitosan polymer matrix. Synthesized bio-composites were characterised with the aid of FTIR, XPS, Thermal analysis, SEM with EDAX and subjected for hexavalent chromium removal from water. Analysis of variance (ANOVA) with 95 % confidence intervals was used to assess the significance of independent variables and their interactions. Adsorption studies were done using batch process and to achieve greater sorption, various influencing parameters were optimized one by one. While investigating one parameter, other parameters were kept unaltered. Optimization was done for the parameters like contact time, dosage of the adsorbent, pH of the medium and presence of co-ions. Contact time and dosage for all the composites was 30 mins and 0.1 g respectively. Amongst the composites, Zirconium loaded binary composite possess high sorption capacity of around 14.8 mg/g. While Calcium and Iron loaded composites exhibit sorption capacity of around 9.8 mg/g and 10.4 mg/g respectively. Presence of other co-ions in the medium doesn't affect the sorption process. Isothermal studies infer the adsorption follows Langmuir model and thermodynamic parameters concludes the endothermic and randomness of the adsorption. The bio-composites can be recycled and used upto three cycles. Field trial was conducted and the composites work well in such conditions.

Hydrogel-Based Adsorbent Material for the Effective Removal of Heavy Metals from Wastewater: A Comprehensive Review

Water is a vital resource that is required for social and economic development. A rapid increase in industrialization and numerous anthropogenic activities have resulted in severe water contamination. In particular, the contamination caused by heavy metal discharge has a negative impact on human health and the aquatic environment due to the non-biodegradability, toxicity, and carcinogenic effects of heavy metals. Thus, there is an immediate need to recycle wastewater before releasing heavy metals into water bodies. Hydrogels, as potent adsorbent materials, are a good contenders for treating toxic heavy metals in wastewater. Hydrogels are a soft matter formed via the cross-linking of natural or synthetic polymers to develop a three-dimensional mesh structure. The inherent properties of hydrogels, such as biodegradability, swell-ability, and functionalization, have made them superior applications for heavy metal removal. In this review, we have emphasized the recent development in the synthesis of hydrogel-based adsorbent materials. The review starts with a discussion on the methods used for recycling wastewater. The discussion then shifts to properties, classification based on various criteria, and surface functionality. In addition, the synthesis and adsorption mechanisms are explained in detail with the understanding of the regeneration, recovery, and reuse of hydrogel-based adsorbent materials. Therefore, the cost-effective, facile, easy to modify and biodegradable hydrogel may provide a long-term solution for heavy metal removal.

The key role of microscopic structure and graphene sheet-high homogenization in the high rate capability and cycling stability of Ni-Co LDH

As a typical electrode material in Faraday supercapacitors (FSs), Ni(OH)2 has some intrinsic issues such as low electrical conductivity and structural instability, resulting in its low performance. In view of these issues, we design a multifunctional nanostructure, rigid nanosheet-interlaced structure of Ni-Co LDH/graphene to improve the electrical conductivity and structural stability of Ni(OH)2. Under the high shear applied by a high shear mixer (HSM) and the regulation of polyvinylpyrrolidone (PVP), the designed structure is realized. Benefitting from the well-designed structure and improved electrical conductivity of the graphene sheet-high homogenization, Ni-Co LDH/graphene presents the expected performance. It exhibits a high specific capacity of 1020 C g-1 at a low current density of 2.7 A g-1 and excellent high rate performance (637.5 C g-1 at 62.5 A g-1). The asymmetrical supercapacitors (ASCs) assembled with the composite as the positive material show high energy density (86.5 W h kg-1 at a power density of 695.7 W kg-1). Due to the improved structural stability, the ASCs also exhibit high cycling stability (a capacity retention of 97.8% after 10 000 charge-discharge cycles).

A review on acrylic based hydrogels and their applications in wastewater treatment

The acrylic based hydrogels have attracted the attention of many researchers in the field of pollutants adsorption such as dyes and metal cations due to their high swelling and adsorption capacities. This review introduces acrylic based hydrogels and focuses on their adsorption properties. We first described the methods for synthesizing hydrogels. Usual methods of characterization of acrylic based hydrogels such as swelling, adsorption capacity and desorption efficiency of the pollutants have been investigated. In addition, the adsorption isotherm and kinetic models which determine the mechanism of pollutants' adsorption by hydrogels have been introduced and relations that determine the values of thermodynamic parameters which define accomplishment of adsorption process have been investigated. In the following sections, a perfect insight has been provided on natural and synthetic acrylic based hydrogels. The effective parameters of swelling and adsorption by acrylic based hydrogels have been reviewed and the mechanism of pollutant's adsorption by acrylic based hydrogels has been discussed.

Polymer Stabilized Fe3O4-Graphene as an Amphiphilic Drug Carrier for Thermo-Chemotherapy of Cancer

In light of the growing interest in the search for cheap and effective solutions for cancer treatment, we report a simple one pot synthesis of polymer stabilized iron oxide-graphene (PIG) that could be realized on a large scale. The structural (Fe3O4 particle size of ∼11 nm), functional (various oxygen containing moieties), and magnetic (moment of ∼43 emu/g) properties of PIG are explored using various characterization techniques for possible biomedical applications. PIG shows good colloidal stability and is biocompatible even at higher concentrations (2.5 mg/mL) by virtue of cross-linking polymers. The biocompatibility of the composite has been tested using HeLa cell lines by computing the percentage of the reactive oxygen species through the 2,7-dichlorofluorescein (DCF) intensity level. PIG has the ability to load and release both hydrophobic and hydrophilic drugs with a good loading efficiency and capacity. The dug loading efficiency of PIG is measured to be ∼87% and ∼91% for doxorubicin (DOX) and paclitaxel (PTXL), respectively. Under an AC magnetic field, superparamagnetic PIG (2.5 mg/mL) takes less than 16 min to reach the stable hyperthermia temperature, suggesting it as a good anticancer material. A time-dependent cellular uptake of doxorubicin-conjugated PIG has been studied to optimize the parameters for thermo-chemotherapy of cancer. The synergetic effect of both the drug and hyperthermia is observed in the killing of the cancerous cells, verified by computing the cell apoptotic population using a flow cytometer. However, it has been noticed that, even in the absence of chemotherapy, PIG shows good antiproliferative activity with thermotherapy alone.