Physicochemical Characterization of Surface Water from the Wakasso Gold Mining Site (Adamawa, Cameroon) and Heavy Metal Removal Using Water Hyacinth (Eichhornia crassipes) Roots.

Abstract

This study investigates the physicochemical characteristics of surface water from the artisanal and semi-mechanized gold mining site of Wakasso (Adamawa, Cameroon) and evaluates the potential of water hyacinth (Eichhornia crassipes) roots for heavy metal removal through adsorption. Three water samples (E1, E2, E3) were collected along the Lom River, and physicochemical parameters (pH, electrical conductivity, turbidity) were measured in situ. Chemical analyses were performed for seven major ions (Ca²⁺, Mg²⁺, Cl⁻, NO₃⁻, HCO₃⁻, SO₄²⁻, CN⁻) and four heavy metals (As, Hg, Pb, Fe) using atomic absorption spectrometry and ion chromatography. Results revealed heavy metal concentrations ranging from 0.139 to 12.26 mg/L for arsenic, 0 to 0.002 mg/L for mercury, 0.03 to 2.523 mg/L for lead, and 0.24 to 6.341 mg/L for iron. Except for mercury, these concentrations exceeded WHO (2017) and Cameroonian drinking water standards, indicating significant contamination of surface water associated with mining activities. Health issues observed among residents, including diarrhea, respiratory problems, and skin lesions, are likely linked to the widespread use of Lom River water for domestic purposes. Adsorption treatment using water hyacinth roots demonstrated removal efficiencies of 70% (As), 80% (CN⁻), 12% (Pb), and 9% (Fe), highlighting the potential of this low-cost biosorbent for wastewater treatment, though optimization is required to enhance performance. The Langmuir and Freundlich isotherm models were applied to describe the adsorption process, with the Langmuir model providing the best fit (R² = 0.987), suggesting monolayer adsorption on homogeneous surfaces. Kinetic studies revealed that the pseudo-second-order model (R² = 0.993) better described the adsorption mechanism, indicating chemisorption as the rate-limiting step.