a b s t r ac tIn this study, the use of cheap unmodified and acid-modified agricultural waste primed from groundnut husk as adsorbents for the removal of Cu(II) ions from aqueous solution were examined in a batch process under different experimental conditions. Fourier transform infrared characterization of the adsorbent before and after the adsorption process revealed the likely involvement of various functional groups such as -COOH, -C=O, -NH 2 and -OH − groups. Structural and morphological changes of the biomass were equally observed by X-ray diffraction and scanning electron microscopy analysis before and after adsorption of copper ions. Optimum experimental conditions were obtained to be the initial metal concentration of 50 mg L −1 , contact time of 70 min, biomass dosage of 0.03 g and hydrogen ion concentration of 5.0. The kinetic studies showed that the sorption pattern of both biomasses followed pseudo-second-order model, while the isotherms studies revealed that the adsorption data were well governed by Freundlich adsorption isotherm. The monolayer adsorption capacity for unmodified groundnut husk was found to be 14.525 and 20.146 mg g −1 for acid-modified groundnut husk as computed from the Langmuir model equation. It can thus be concluded that waste groundnut husk can be used as a low cost and environmentally friendly adsorbent for Cu(II) ions removal from aqueous solution.

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Electrospun ZnO was deposited on a glass substrate from zinc acetate dihydrate (Zn(CH 3 COO) 2 .2H 2 O) with polyvinyl acetate (PVAc) polymer dissolved in N, N, dimethyl formamide (DMF) and annealed in the presence of oxygen until organic molecules were decomposed. The resultant fibre was characterized using scanning electron microscope with energy dispersive spectrophotometry (SEMEDS), Fourier transform infrared (FTIR), and Rutherford backscattering spectroscopy (RBS). SEMEDS and FTIR exhibited a total decomposition of the organic precursor. The mean fibre width was found to be 260 nm, and fibre thickness was measured at 460 nm. XRD patterns indicate that ZnO was corundum with the hexagonal wurtzite structure. The crystallite size was determined by the Debye formula to be 54 nm. The optical analysis indicated that the percentage transmittance increased after calcination. The material band gap for this electrospun ZnO fibre was found to be 3.28 eV. The material optical parameters such as dispersion energy, average oscillator strength, and single oscillator strength were also calculated. The optical conductivity and dielectric plot demonstrated that the material conductivity and dielectric properties increase with increasing photon energy and increase sharply around the material energy bandgap. The Urbach tail analysis of the materials shows that they obey the Urbach rule. Therefore, the n-type electrospun ZnO fibre high refractive index is attributable to the presence of excess oxygen.

Pb2+ is considered to be a very toxic pollutant in the aquatic environmental media. Biopolymeric chitosan synthesized from snail shell has been studied for its potential to remove heavy metals from aqueous solution. The experiments were conducted in the range of 1–50 mg/L initial Pb2+ concentration at 298 K. The effects of pH, adsorbent dosage and contact time on the adsorptive property of the adsorbent were investigated and optimized. The derived chitosan was characterized using Fourier transform infrared spectrometer (FT-IR) and X-ray florescence (XRF). The experimental data obtained were analysed using the Langmuir and Freundlich adsorption isotherm models. The Langmuir model and pseudo second order kinetic model suitably described the adsorption and kinetics of the process with regression coefficients of 0.99 and 1.00, respectively. Sodium hydroxide was a better desorbing agent than hydrochloric acid and de-ionized water. From the results obtained, it is concluded that synthesized biopolymers from land snail shells has the potential for the removal of Pb2+ from aqueous solutions.

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