Polyvinyl alcohol (PVA) demonstrates chemical stability and biocompatibility and is widely used in biomedical applications. The porous bamboo charcoal has excellent toxin absorptivity and has been used in blood purification. In this study, bamboo charcoal nanoparticles (BCNPs) were acquired with nano-grinding technology. The PVA and PVA/BCNP nanocomposite membranes were prepared and characterized by the tensile test, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD). Results showed that the tensile strength and elongation of the swollen PVA membranes containing 1% BCNPs (PB₁) were significantly greater than those of PVA and other PVA/BCNP composite membranes. In addition, the major absorption band of OH stretching in the IR spectra shifted from 3262 cm-¹ for PVA membrane containing 1% BCNP to 3244 cm-¹ for PVA membrane containing 20% BCNP. This blue shift might be attributed to the interaction between the PVA molecules and BCNPs. Moreover, the intensity of the XRD peaks in PVA was decreased with the increased BCNP content. The bioactivity of the nanocomposites was evaluated by immersion in the simulated body fluid (SBF) for seven days. The mineral deposition on PB₅ was significantly more than that on the other samples. The mineral was identified as hydroxyapatite (HA) by XRD. These data suggest that the bioactivity of the composite hydrogel membranes was associated with the surface distribution of hydrophilic/hydrophobic components. The PVA/BCNP composite hydrogels may have potential applications in alveolar bone regeneration.

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Poly(vinyl alcohol) Nanocomposites Reinforced with Bamboo Charcoal Nanoparticles: Mineralization Behavior and Characterization

Removal of toxic metal ions from landfill leachate by complementary sorption and transport across polymer inclusion membranes.

Heavy metals from industrial processes are of special concern because they produce chronic poisoning in the aquatic environment. More strict environmental regulations on the discharge of toxic metals require the development of various technologies for their removal from polluted streams (i.e. industrial wastewater, mine waters, landfill leachate, and groundwater). The separation of toxic metal ions using immobilized materials (novel sorbents and membranes with doped ligands), due to their high selectivity and removal efficiency, increased stability, and low energy requirements, is promising for improving the environmental quality. This critical review is aimed at studying immobilized materials as potential remediation agents for the elimination of numerous toxic metal (e.g. Pb, Cd, Hg, and As) ions from polluted streams. This study covers the general characteristics of immobilized materials and separation processes, understanding of the metal ion removal mechanisms, a review of the application of immobilized materials for the removal of toxic metal ions, as well as the impacts of various parameters on the removal efficiency. In addition, emerging trends and opportunities in the field of remediation technologies using these materials are addressed.

Immobilized materials for removal of toxic metal ions from surface/groundwaters and aqueous waste streams.

This article aims to study the effect of the chemical composition of the Egyptian kaolins on the performance of the low cost kaolin-based zeolites toward Pb 2+ removal. In this work, different Egyptian kaolins collected from Saint Catherine, Kalabsha and Dehessa (KS, KK and KD, respectively) were used in the preparation of the corresponding Na-Y zeolites (ZS, ZK and ZD). X-ray Fluorescence (XRF), X-ray diffraction (XRD) and atomic absorption analyses were recorded. XRF and XRD indicate that the zeolitic contents in the prepared samples are proportional to the kaolinite contents in the corresponding kaolins. The difference in the removal efficiency between zeolites depends on the experimental conditions. Generally, the order of Pb 2+ loading and Na + release is ZS > ZK > ZD, which is in accordance with the zeolitic contents in each sample. From sorption isotherms, maximum sorbed amounts of Pb 2+ were 299.6, 299.3 and 260.6 meq/100 g for ZS, ZK and ZD, respectively. Comparison with previous studies shows that the maximum loading capacities of zeolites are higher than the commonly used; and it is also comparable to ion exchange resins. For all zeolites, in Pb 2+ loading experiments, the relation between released and loaded equivalents of positive charges was not stoichiometric. We concluded that the loading process involves competition between three processes: (a) precipitation of some Pb 2+ as hydroxides, (b) ion exchange and (c) chemisorption of Pb 2+ on zeolite surfaces. During Pb 2+ loading processes, the equivalent amount of loaded Pb 2+ is always higher than that of the released Na + suggesting the predominance of the chemisorption mechanism.

Masaki Kanemitsu

Papers

Synthesis and application of a highly efficient polyvinylcalix[4]arene tetraacetic acid resin for adsorptive removal of lead from aqueous solutions