Removal of Lead and Chromium from Industrial Wastewater Using Lyophilized Aspergillus flavus Biomass

Industrial battery wastewater frequently contains hazardous concentrations of lead (Pb) and chromium (Cr), posing serious environmental and public health risks if discharged without adequate treatment. Developing cost-effective and reliable removal strategies is therefore essential. In this study, non-living fungal biomass of Aspergillus flavus was evaluated as a biosorbent for the removal of Pb and Cr from real industrial wastewater. Two biomass preparation methods were compared: oven-drying and freeze-drying (lyophilization). Batch experiments were conducted at 30°C using a factorial experimental design to examine the influence of pH (1.5, 4, and 5) and contact time (0.5–48 h) on metal removal efficiency. The freeze-dried (lyophilized) biomass demonstrated markedly faster uptake and higher removal efficiency than oven-dried biomass, achieving complete removal (100%) of both Pb and Cr within 0.5 h at pH 5. Prolonged contact tests up to 48 h showed no detectable re-release of the adsorbed metals, indicating stable binding of the metal ions to the fungal matrix. The pronounced pH dependence suggests that ion exchange and interactions with functional groups on the cell wall play a key role in the biosorption process. Experimental data were expressed as mean ± standard deviation, and differences among treatments were evaluated at a significance level of p < 0.05. These findings highlight the potential of freeze-dried (lyophilized) A. flavus biomass as an efficient and rapid biosorbent for treating metal-contaminated industrial effluents.