Eggshell-activated carbon from water hyacinths for heavy metal removal from wastewater: Isotherm and kinetic studies
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Date
2026-07-08
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI journals
Abstract
Heavy metals (HMs) such as copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr) and zinc (Zn) from industrial activities are discharged into nearby water resources after treatment. In the present study, the potential of utilizing chemically activated carbon derived from water hyacinths as a sustainable and low-cost adsorbent for heavy metal removal from industrial wastewater from the Nakawa industrial area, Uganda was investigated. The measured physicochemical parameters of wastewater (temperature, pH, electrical conductivity, total dissolved solids, turbidity, dissolved oxygen, chlorides and total hardness) varied significantly among the three sampled sites (p < 0.05), except for pH. Similarly, the concentration of the HMs in the samples (0.54 ± 0.04 mg L−1 for Cr to 93.54 ± 0.07 mg L−1 for Pb) varied significantly between sites (p < 0.05), exceeding the maximum permissible limits of Cd, Pb, Cr, Cu and Zn specified in the National Environment Standards for Discharge of Effluent into Water or Land. The water hyacinth biomass was activated using eggshell powder and phosphoric acid, followed by thermal treatment. Characterization using Fourier-transform infrared spectroscopy and scanning electron microscopy confirmed that there was improvement in its surface functionality and porosity post activation. Batch adsorption experiments indicated that optimal removal of the HMs was achieved at pH 4–5, contact time of 90 min, and 1.0 g of adsorbent. Maximum adsorption capacities of Pb, Cd, Cu, Cr and Zn were in the range of 1.04–8.36 mg g−1. Under the optimized conditions, the eggshell-activated carbon derived from water hyacinths had removal efficiencies of 91.2 ± 9.1% (range: 71.3–100%). Adsorption occurred through both monolayer and multilayer coverage, as indicated by the experimental data which fitted well to the Freundlich isotherm (Cd2+, Pb2+, Zn2+ and Cu2+ ions) and Langmuir isotherm model (Cr3+ ions). These results support the potential of water hyacinth-derived activated carbon as an ecofriendly alternative for treating low concentrations of these HMs in industrial wastewater.
Description
This research aligns with Sustainable Development Goal (SDG) 6 (Clean Water and Sanitation), Target 6.3, by promoting technologies that reduce water pollution and improve wastewater treatment. It also contributes to SDG 9 (Industry, Innovation and Infrastructure), Target 9.4, by developing a cost-effective adsorbent for sustainable industrial wastewater management. Regarding SDG 12 (Responsible Consumption and Production), Target 12.5, the study transforms invasive water hyacinths and waste eggshells into valuable treatment materials, advancing circular economy principles. The research supports Uganda’s National Development Plan IV (NDP IV), especially the Natural Resources, Environment, Climate Change, Land and Water Management Programme and the Sustainable Energy Development Programme, by promoting pollution control, better water resource management, and environmentally friendly technologies. The findings provide evidence for green wastewater treatment solutions that help industries meet environmental standards, improve ecosystem health, enable waste reuse, and support sustainable industrial growth in Uganda.
Keywords
Adsorption, Eichhornia Crassipes, Kinetics, Optimization
Citation
Atumanye, C., Bbumba, S., Nsubuga, H., Kiganda, I., Omara, T., & Kwetegyeka, J. (2026). Eggshell-activated carbon from water hyacinths for heavy metal removal from wastewater: Isotherm and kinetic studies. Journal of Xenobiotics, 16(4), 126.