Influence of UV degradation of bioplastics on the amplification of mercury bioavailability in aquatic environments

Bioplastics have emerged to minimize the ecological footprint of non-degradable plastics. However, the effect of their degradation in aquatic systems, including the interaction with toxic metals, is still unexplored. In this work, the influence of UV-aging on structure, chemistry, wettability, rigidity, and Hg-sorption of commercially available bioplastic (BIO)- and polyethylene (PE)-based films was studied. To mimetize the materials disposal in fresh-/saltwaters, non-saline/saline aqueous solutions were used in Hg-sorption studies. ATR-FTIR spectra revealed that the BIO film was a coblended starch/polyester-based material, whose microstructure, physicochemical, and mechanical properties changed after UV-aging to a higher extent than in PE film. AFM and kinetic modelling pointed out electrostatic interactions/complexation as the mechanisms involved in the increased Hg-sorption by the UV-aged BIO film. An increased salinity did not impair its Hg-sorption. Therefore, when disposed in aquatic systems, starch/polyester-based bioplastics can play a potential vector for amplifying Hg along the food chain.

Design and characterization of PANI/starch/Fe2O3 bio composite for wastewater remediation

A new synthesized polyaniline/starch/hematite bio composite (PANI/S/Fe₂O₃ BC) has been studied as an effective material for on-site water remediation. PANI/S/Fe₂O₃ BC was developed by combining the techniques of co-precipitation and interfacial polymerization in the presence of aqueous starch solution in an acidic medium under ultrasonic irradiation. The nano-morphologies and structures of the designed PANI/S/Fe₂O₃ BC were evaluated by various techniques relative to PANI and Fe₂O₃ nanoparticles. In single and multiple systems, PANI/S/Fe₂O₃ BC was evaluated as a possible adsorbent for different heavy metals, including As³⁺, Zn²⁺, and Co²⁺, relative to PANI and Fe₂O₃ nanoparticles. In terms of pH value, operating temperature, initial heavy metal concentration, contact time, adsorbent dose and competitive ions in the solutions, the adsorption process was optimized. For 92% overall adsorption of Co²⁺ and 100% overall adsorption of both As³⁺ and Zn²⁺, the adsorption equilibrium was achieved within 60 and 120 min, respectively. In addition, adsorption thermodynamic analysis shows that the As³⁺ ions adsorption process was not random and the pseudo-second-order fitted with experimental results. Moreover, PANI/S/Fe₂O₃ BC was evaluated as an antibacterial agent against Gram-negative bacteria (Salmonella typhimurium) and Gram-positive bacteria (S. aureus, Methicillin-Resistant Staphylococcus, Aureus Clinical isolate and Bacillus subtilis). The reported performances indicated that the PANI/S/Fe₂O₃ BC is a potent candidate for industrial water bioremediation.

A review on grafting of hydroxyethylcellulose for versatile applications

Hydroxyethylcellulose (HEC) is a biocompatible, biodegradable, nontoxic, hydrophilic, non- ionic water soluble derivative of cellulose. It is broadly used in biomedical field, paint industry, as a soil amendment in agriculture, coal dewatering, cosmetics, absorbent pads, wastewater treatment and gel electrolyte membranes. Industrial uses of HEC can be extended by the its grafting with different polymers including poly acrylic acid, polyacrylamide, polylactic acid, polyethyleneglycol, polydimethyleamide, polycaprolactone, polylactic acid and dimethylamino ethylmethacrylate. This permits the formation of new biomaterials with improved properties and versatile applications. In this article, a comprehensive overview of graft copolymers of HEC with other polymers/compounds and their applications in drug delivery, stimuli sensitive hydrogels, super absorbents, personal hygiene products and coal dewatering is presented.

Copper Silicate Hollow Microspheres-Incorporated Scaffolds for Chemo-Photothermal Therapy of Melanoma and Tissue Healing

The treatment of melanoma requires complete removal of tumor cells and simultaneous tissue regeneration of tumor-initiated cutaneous defects. Herein, copper silicate hollow microspheres (CSO HMSs)-incorporated bioactive scaffolds were designed for chemo-photothermal therapy of skin cancers and regeneration of skin tissue. CSO HMSs were synthesized with interior hollow and external nanoneedle microstructure, showing excellent drug-loading capacity and photothermal effects. With incorporation of drug-loaded CSO HMSs into the electrospun scaffolds, the composite scaffolds exhibited excellent photothermal effects and controlled NIR-triggered drug release, leading to distinctly synergistic chemo-photothermal therapy of skin cancer both in vitro and in vivo. Furthermore, such CSO HMSs-incorporated scaffolds could promote proliferation and attachment of normal skin cells and accelerate skin tissue healing in tumor-bearing and diabetic mice. Taken together, CSO HMSs-incorporated scaffolds may be used for complete eradication of the remaining tumor cells after surgery and simultaneous tissue healing, which offers an effective strategy for therapy and regeneration of tumor-initiated tissue defects.

Biosorption potential of Gum ghatti-g-poly(acrylic acid) and susceptibility to biodegradation by B. subtilis

This article reports the biosorption potential of Gum ghatti (Gg)-grafted-acrylic acid (AA) polymer and its susceptibility to biodegradation by Bacillus subtilis (BS) in two different liquid media, i.e. phosphate buffered saline (PBS) and mineral salt medium (MSM). The progress of biodegradation was monitored after every 15 days using FT-IR and SEM techniques. The degradation of the polymer was further evidenced by a loss of weight of 23.2% and 27% in BS-MSM and BS-PBS, respectively, after 60 days. The AA-grafted polymer was then utilized for the removal of Pb(II) and Cu(II) from aqueous solution. The adsorption isotherm data were studied using Langmuir, Freundlich, Temkin, Flory-Huggins and Dubinin-Kaganer-Radushkevich isothermal models. High values of correlation coefficients confirmed the applicability of Langmuir isotherm model used to determine the adsorption capacity of the AA-grafted polymer. The maximum adsorption capacity was found to be 84.74 mg/g for Cu(II) and 310.55 mg/g for Pb(II). Kinetic data were evaluated using pseudo first order, pseudo second order, Elovich, intraparticle diffusion and liquid film diffusion models. The experimental kinetic data fitted well with the pseudo second order rate model.

Natural Polysaccharides as Treatment Agents for Wastewater

This chapter gives an account of recent developments in biopolymers with an emphasis on natural polysaccharides as treatment agents in wastewater remediation. Almost all sources of water around the world are polluted to some degree, owing to a heavy influx of industrial effluents, domestic and agricultural wastes. These discharges vary from simple nutrients to highly toxic hazardous chemicals. Numerous approaches have been studied for the development of cheaper and more effective water remediation agents containing natural polymers. Among these, natural polysaccharides deserve particular attention. These materials have proved to be better treatment alternatives compared to their synthetic counterparts because of their particular structure, physicochemical characteristics, chemical stability, high reactivity and excellent selectivity towards aromatic compounds, metals and other contaminants that cause water pollution.

Synthesis, characterization and applications of a new cation exchanger tamarind sulphonic acid (TSA) resin

A new composite cation exchanger, tamarind sulphonic acid (TSA) resin has been synthesized. The chemically modified TSA ion exchange resin has been used for the removal and preconcentration of Zn2+, Cd2+, Fe2+, Co2+ and Cu2+ ions in aqueous solution and effluent from the Laxmi steel plant in Jodhpur, India. This type of composite represents a new class of hybrid ion exchangers with good ion exchange capacity, stability, reproducibility and selectivity for toxic metal ions found in effluent from the steel industry. The characterization of the resin was carried out by determining the ion-exchange capacity, elemental analysis, pH titration, Fourier transform infrared spectra and thermal analysis. The distribution coefficients (K(d)) of toxic metal ions were determined in a reference aqueous solution and the steel plant effluent at different pH values; the absorbency of different metal ions on the TSA resin was studied for up to 10 cycles. The adsorption of different metal ions on TSA resin follows the order: Co2+ > Cu2+ > Zn2+ > Fe2+ > Cd2+. The ion exchange capacity of TSA resin is 2.87%.

A novel starch-based adsorbent for removing toxic Hg(II) and Pb(II) ions from aqueous solution

A novel effective starch-based adsorbent was prepared through two common reactions, which included the esterification of starch with excess maleic anhydride in the presence of pyridine and the cross-linking reaction of the obtained macromonomer with acrylic acid by using potassium persulphate as initiator. The percentage of carboxylic groups of the macromonomer ranged from 14% to 33.4%. The cross-linking degree of the adsorbent was tailored with the amount of acrylic acid which varied from 10wt% to 80wt%. Both Fourier transform infrared spectra and thermogravimetric analysis results verified the structure of the adsorbent. The maximum gel fraction and swelling ratio of the adsorbent were about 72% and 6.25, respectively, and they were able to be adjusted with the amount of monomers. The weight loss percentage of the adsorbent could reach 96.9% after immersing in the buffer solution that contained α-amylase for 14h. It was found that the adsorption capacities of the adsorbent for lead and mercury ions could be 123.2 and 131.2mg/g, respectively. In addition, the adsorbent was able to remove ca. 51-90% Pb(II) and Hg(II) ions that existed in the decoctions of four medicinal herbals.

Synthesis and Swelling Behavior of Hydrogels Based on Grafted Chitosan

The grafting of poly (acrylic acid) and /or acrylamide onto biopolymer chitosan were carried in order to obtain hydrogel materials- The grafting reactions were carried out in a homogeneous aqueous phase by using potassium persulfate in combination with ferrous ammonium sulfate as redox initiator system in the case of acrylic acid and potassium persulfate alone in the case of acrylamide The percentage of grafting was found to depend on the relative amount of monomer to chitosan, initiator and ferrous ion concentration, volume of the aqueous phase as well as reaction time and reaction temperature. In the case of acrylic acid a maximum grafting of 1800% was obtained, whereas with acrylamide the optimum percentage of grafting attained was near 400%. Evidence of grafting was obtained from comparison of FTIR of the grafted and ungrafted chitosan as well as solubility characteristics and swelling behavior of the products. The swelling degree of the grafted chitosan samples was determined at two different pH values. The percentage of grafting influenced the degree of swelling of the grafted chitosan, in different manner depending on the nature of the grafted chains, where values as high as 40 was observed.