Isotherm and Kinetic Studies on Escherichia colifor Cadmium-Contaminated Wastewater Treatment

Background and Objective: Cadmium (Cd) contamination poses a major environmental and public health concern due to its toxicity, persistence, and bioaccumulation. Conventional remediation methods are often costly and inefficient, generating secondary pollution. This study aimed to evaluate the biosorption potential ofEscherichia coli isolated from a plastic recycling plant for the removal of Cd (II) ions from aqueous solutions, using isotherm and kinetic modeling to characterize adsorption behavior. Materials and Methods: Soil samples from a plastic recycling site were processed to isolate E. coli, identified through Gram staining and biochemical tests. Biomass was prepared and used in batch biosorption experiments under varying pH, contact time, initial Cd concentration, and biomass doses. Residual Cd levels were measured using atomic absorption spectrophotometry (AAS). Adsorption data were analyzed using Langmuir and Freundlich isotherms and kinetic models, including pseudo-first and pseudo-second order equations. Results: Maximum Cd (II) uptake occurred at pH 7, with equilibrium reached within 24-28 hrs. Adsorption capacity increased with initial Cd concentration until saturation. The pseudo-first order kinetic model best fitted the data, while the Langmuir isotherm showed the highest correlation, indicating monolayer adsorption on homogeneous sites. The maximum adsorption capacity was 50.013 mg/g. Conclusion: The findings confirm that E. coli biomass serves as an effective, low-cost biosorbent for Cd (II) removal under laboratory conditions. Its performance aligns with established biosorption models, supporting its potential application in wastewater treatment. Further studies on regeneration efficiency, column operations, and molecular adsorption mechanisms are recommended for practical implementation.