The quest to synthesize nanomaterials with improved properties, but less undesirable effects on the environment necessitated this research. Zinc Oxide (ZnO) nanoparticles and zinc oxide-silver (ZnO-Ag), zinc oxide-copper (ZnO-Cu) nanocomposites were synthesized with pure eco-friendly dye extracted from Bridelia ferruginea, zinc acetate (Zn(CH 3 COO) 2 ) as host, copper acetate (Cu (CH 3 COO) 2 ), and silver nitrate (AgNO 3 ) as dopant precursors. Phytochemical screening of dyes showed high, presence of phenols and terpenoids. The nanomaterials were characterized by Fourier-transform infrared, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, transmission electron microscopy and ultraviolet-visible spectroscopy. The results showed the capping agents in the dyes were responsible for reducing the bulk materials. The crystallinity of the nanomaterials were found to be 19.02, 18.98 and 18.90 nm for the ZnO, ZnO-Ag and ZnO-Cu nanoparticles respectively. The ZnO nanoparticles were flakelike in shape, whereas the Cu and Ag doped particles were spherical. An optical bandgap of 4.73 eV was recorded for the dye and 3.24 eV for the ZnO nanoparticles. This was narrowed to 3.18 and 3.13 eV by silver and copper dopant respectively. These results showed the nanoparticles as a potential agent for photovoltaics and other optical applications.
Starch is a biopolymer with outstanding economic and environmental friendly attributes which has driven technological innovations to enhance its applications in food and nonfood industries. Starch is constituted by O-H groups with valency and electronic characteristics that can initiate adsorption of aqueous heavy metal ions (AHMIs). However, this can be enhanced using various modification sequences. A common procedure is the cross-linking and substitution of the O-H groups via esterification and/or etherification reactions to produce starch derivative adsorbents (SDAs) with improved structural and functional properties for adsorption of AHMIs. The efficiency of SDAs developed using these procedure depends on the botanical source of the native starch base, porosity and structural stability of the derivative (i.e. degree of cross-linking), substituted functional group(s), degree of substitution (DS) and the steric/conformation effects of the substituted groups. Many works have been done to optimize these factors, and this review highlighted some of the tailored procedures and the results obtained.
A B S T R A C TThe relative cadmium sorption ability of unmodified and aminated lignins was examined as a function of solution pH, sorbent-sorbate resident time and ratio, concentration and temperature. Experimental results showed that the surface characteristics of both the unmodified and aminated lignins were favourable to effective cadmium ions sorption from aqueous solutions. Sorption of cadmium was dependent on equilibrium solution pH, as maximum removal was attained at pH 5. The Langmuir and Freundlich isotherm models fitted the experimental data. The biosorption of cadmium onto unmodified and aminated lignins was rapid and equilibrium was attained within 120 min. The sorption kinetic data revealed that the biosorption of cadmium onto these biosorbents followed pseudo-second-order model. This was further supported by Elovich and intraparticle diffusion models. The process was endothermic and DGẘ as positive showing non-spontaneity of the process within the studied temperature range.
In this study, series of experiments were carried out in batch in order to examine the possibility of thiourea doped silica composite for the removal of lead under different experimental conditions. Adsorption of lead (II) ions was investigated with the difference in the parameters of pH, contact time, and lead (II) ions concentration. The adsorption of lead followed pseudo-second-order rate kinetics. Intra-particle diffusion was established not to be the sole rate-controlling step. Thermodynamic studies tell that the adsorption of lead was endothermic and spontaneous, with a good affinity of the adsorbent. Various isotherm models viz, Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Harkins-Jura isotherms were used to evaluate the equilibrium data. The Freundlich and Temkin models were established to be in actual agreement with the experimental data with high R 2 , low RMSE, and low χ 2 values. The maximum adsorption capacity calculated from Langmuir isotherm was 42.31 mg/g at optimum condition of pH 4 and contact time of 60 min.
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