Mitigating Waterborne Health Risks Through Malachite Green Biosorption Using Tea Waste-Derived Material

Introduction: Malachite green (MG) is a synthetic dye extensively used in the textile and aquaculture industries, known for its toxicity, bioaccumulation potential, and environmental persistence which poses significant public health risks. This study investigates the biosorption performance of raw tea waste (RTW) and iron-coated tea waste (FeTW) for MG removal as a low-cost and sustainable water treatment solution. Methods: A laboratory-based batch biosorption experiment was conducted under parameters of contact time, biosorbent dosage and initial MG concentration using biosorbents of RTW and FeTW. The MG removal efficiency was quantified using a Hach DR900 spectrophotometer. Functional group characterization was conducted via FTIR spectroscopy, and adsorption behaviours were analysed using Langmuir and Freundlich isotherm models. Results and Discussion: FeTW demonstrated superior performance compared to RTW under all conditions. A maximum removal efficiency of 68.54% was achieved using 0.5g of FeTW at an initial MG concentration of 25mg/L within 60minutes. FTIR analysis revealed enhanced hydroxyl group intensity at 3360cm⁻¹ and the appearance of Fe–O bonds at 560cm⁻¹, confirming successful surface modification. The Langmuir isotherm model best described the biosorption behavior with R² of 0.9901 and maximum biosorption capacity (qm) of 3.12mg/g. The low separation factor (RL) value of 0.00025 indicated highly favorable biosorption. Conclusion: These findings demonstrate the potential of FeTW as an eco-friendly biosorbent to reduce human exposure to MG, a known carcinogenic contaminant in water systems. Iron modification significantly enhances the biosorption capacity of tea waste for MG removal and contributes to safer water quality and reduced public health risks.