Department of Chemistry

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Browsing Department of Chemistry by Subject "Adsorbents"

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    Investigation of activated water hyacinth (Eichhornia crassipes) -based adsorbents for removal of selected heavy metals in wastewaters from the Nakawa industrial area, Kampala
    (Kyambogo University (Unpublished work), 2025-04) Atumanye, Claire
    Industrial activities in the Nakawa Industrial Area, Kampala, have led to the discharge of toxic heavy metals, including Copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr), and Zinc (Zn) into local wastewater streams, posing significant environmental and public health threats. These metals are non-biodegradable, highly toxic, and tend to accumulate in living organisms, leading to long-term health risks. Conventional methods for heavy metal removal, such as chemical precipitation and ion exchange, are often cost-prohibitive, particularly for developing regions, and are ineffective at low metal concentrations. This study investigated the feasibility of using chemically activated water hyacinth (Eichhornia crassipes) biomass, an invasive aquatic plant, as a cost-effective and environmentally sustainable adsorbent for the removal of heavy metals from industrial wastewater. Water hyacinth biomass was subjected to chemical activation using both eggshell powder and 0.5 M phosphoric acid (H₃PO₄) followed by thermal treatment in a muffle furnace. Characterization of the activated adsorbent was performed using Fourier Transform Infrared Spectroscopy (FTIR) to identify the surface functional groups and Scanning Electron Microscopy (SEM) to observe the surface morphology, elemental composition and porosity of the adsorbent. The results indicated that chemical activation significantly enhanced the surface properties of the water hyacinth, increasing its porosity and introducing functional groups capable of binding heavy metals. Batch adsorption experiments were conducted to evaluate the adsorbent's capacity for removing Cu, Pb, Cd, Cr and Zn from both synthetic and real industrial wastewater samples. Optimal adsorption conditions were determined by varying key parameters, including particle size, solution pH, contact time and adsorbent mass. The optimal pH for metal removal was found to range from 4.0 to 5.0, with a contact time of 90 minutes and an adsorbent dosage of 1.0 g. Under these conditions, the maximum adsorption capacities for Pb, Cd, Cu, Cr and Zn were 7.26 mg/g, 10.21 mg/g, 5.33 mg/g, 1.04 mg/g and 8.36 mg/g, respectively. Kinetic studies revealed that the adsorption process for Cd2+, Zn2+ and Cr3+ ions followed a pseudo-second-order kinetic model, indicating chemisorption as the rate-limiting step while, the kinetics of Pb2+ and Cu2+ were better expressed by the pseudo first order model. The equilibrium data were best described by the Freundlich isotherm model, suggesting multilayer adsorption on heterogeneous surfaces with maximum adsorption occurring at specific sites. When tested with real wastewater samples from the Nakawa Industrial Area, the adsorbent exhibited slightly reduced adsorption efficiencies, with capacities of 7.01 mg/g for Pb, 9.93 mg/g for Cd, 5.20 mg/g for Cu, 1.02 mg/g for Cr and 8.06 mg/g for Zn due to the complex composition of the industrial effluent, which contained competing ions and organic matter. This study demonstrates the effectiveness of activated water hyacinth as a low-cost, sustainable adsorbent for the removal of toxic heavy metals from industrial wastewater. The findings provide a practical solution for addressing both environmental contamination and the management of water hyacinth, which is a persistent invasive species in many parts of the world.