ADSORPTION OF CHLOROQUINE AND MALACHITE GREEN DYE USING MODIFIED AGROWASTES AND THEIR ZINC OXIDE COMPOSITE NANOMATERIALS

TOKULA,, BLESSING ENYOJO (2021) ADSORPTION OF CHLOROQUINE AND MALACHITE GREEN DYE USING MODIFIED AGROWASTES AND THEIR ZINC OXIDE COMPOSITE NANOMATERIALS. Masters thesis, Landmark University, Omu Aran, Kwara State.

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Abstract

Indiscriminate industrial and domestic discharge of effluents into water bodies have increased the level of water pollution via anthropogenic activities. Chloroquine (CQ) pharmaceutical and malachite green (MG) dye are a group of emerging contaminants whose unavoidable use leads to traces of them in water bodies. The dire consequences and hazardous effects they induce on both humans and aquatic life have raised concerns amongst researchers and hence the need to develop cheap methods for removing these ecothreatening contaminants. The use of effective and low-cost adsorbent such as rice husk and plantain peel will contribute to the availability of sustainable eco-friendly waste disposal methods and pollutant removal. This research therefore aimed at investigating the adsorption of CQ pharmaceutical and MG dye using modified agro-waste and their zinc oxide nanocomposites. The characterization of adsorbents alongside kinetic studies, mechanism, isotherm and thermodynamics were carried out. Rice husk activated carbon (RHAC) and plantain peel activated carbon (PPAC) serving as base materials were successfully prepared by carbonization and chemical activation using 1 M H3PO4 (Orthophosphoric acid) for 1 hr at 400 oC. Zinc oxide (ZnO) nanoparticles was prepared and loaded on the base materials by precipitation and bottom-up approach using Zinc Nitrate solution (0.45 M) and NaOH (1.0M). The resulting ZnO nanocomposites (RHAC-ZnO-NCs and PPAC-ZnO-NCs) were thereafter calcinated in the muffle furnace for 4 h at 350°C. All adsorbents were characterized by series of physicochemical techniques such as ash and moisture content, volatile matter, Boehm titration, surface area determination using sears method, Iodine number, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and the surface functional group determined via Fourier Transform Infrared (FTIR). PPAC, RHAC, PPAC-ZnO-NCs and RHAC-ZnO-NCs were utilized for adsorptive uptake of malachite green dye and chloroquine via the batch adsorption technique. Various operational parameters (pH, initial concentrations, temperature and agitation time) were investigated to understand their effect on the removal efficiency and quantity adsorbed The physicochemical parameters determined for RHAC, RHAC-ZnO-NCs, PPAC, and PPAC-ZnO-NCs showed pH values within range of 6.53 and 7.21, pHpzc (4.98-6.21), bulk density (0.37-0.88), moisture content (7.31-9.21 %), ash content (12.18- 18.45 %) and volatile matter (30.31-35.64 %). The SEM images showed the existence and availability of pores on the surface of each adsorbent which serve as sites for adsorption. XRD results on the nanocomposites also established the loading of ZnO nanoparticles onto the nanocomposites. The FTIR analysis for all adsorbents showed the presence of functional groups and the corresponding appearance, disappearance and shifting of peaks after loading with ZnO nanoparticles. Adsorption studies showed that adsorbate uptake increased with corresponding increase in temperature. Adsorption of CQ and MG dye was obtained within pH 6-9 at temperature 303 K with highest removal of 95.32 and 76.99 % for CQ and MG dye respectively. Equilibrium data were better described by Freundlich isotherm model and Pseudo second order (PSO) best described the kinetic data. The Langmuir maximum monolayer adsorption capacities (Qmax) calculated for adsorption of CQ ranged from 31.94 to 169.49 mg/g for all adsorbents and Qmax for adsorption of MG ranged from 33.67 to 77.51 mg/g. Qmax values obtained in this study surpassed other reported adsorbents in comparison, thereby indicating their unique quality and better performance ability. Thermodynamic parameters obtained suggested the endothermic nature of the adsorption process as all enthalpy(ΔH) values were positive. The positive entropy (ΔS) values and negative values of free energy change (ΔG) indicated that the adsorption of CQ and MG onto the adsorbents is rapid, random and spontaneous in nature. In conclusion, these adsorbents have been found to be very efficient in removing CQ and MG dye from their solutions. This study may be useful for environmental protection and conservation.

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