The bio-adsorptive treatment of detergent: performance and mechanisms

Abstract

This study develops an optimized hybrid system to treat sodium dodecyl sulfate (SDS)-contaminated wastewater that synergistically integrates microbial biodegradation with physical adsorption within a Response Surface Methodology (RSM) framework. A highly effective SDS-degrading bacterium, Serratia plymuthica strain BSU-AH-03, was isolated from hydrocarbon-contaminated soil. Using a Box-Behnken Design (BBD), the optimal biodegradation conditions (pH 7.9, 20 °C, 300 mg L⁻¹ SDS) yielded a degradation efficiency of 90.46% (predicted 91.27%, R² = 0.981). Subsequently, natural anthracite coal was employed as an adsorbent to polish the effluent. The anthracite exhibited a high surface area (890.9 m² g⁻¹) and a heterogeneous micro-mesoporous structure. Batch adsorption experiments achieved a maximum SDS uptake capacity of 158.7 mg g⁻¹ and a near-complete removal efficiency of 99.58% at 318 K and pH 7. The adsorption process was endothermic (ΔH° = 58.4 kJ mol⁻¹), spontaneous (ΔG° from - 5.15 to -10.65 kJ mol⁻¹), and followed pseudo-second-order kinetics and the Langmuir isotherm, indicating chemisorption as the dominant mechanism. Mechanistic analysis revealed that SDS adsorption involves intra-particle pore diffusion, hydrophobic interactions, electrostatic forces, and hydrogen bonding, culminating in interfacial hemi-micellar aggregation. The synergistic combination of tailored biodegradation and advanced adsorption provides a highly efficient, statistically optimized strategy for the complete remediation of surfactant-laden industrial effluents.