Efficient removal of fecal coliforms from blackwater using polyethyleneimine-modified corn stover biochar: Adsorption performance and mechanisms

Blackwater holds substantial potential for resource recovery; however, its safe utilization is impeded by pathogen contamination. In this work, waste maize straw was converted into polyethyleneimine-modified biochar (PEI-BC) through pyrolysis and functionalization, a material that exhibits high efficacy in adsorbing and removing fecal coliforms from blackwater. Optimal preparation conditions for PEI-BC were determined through Box-Behnken response surface optimization experiments. Characterization results indicate that Polyethyleneimine (PEI) modification significantly increased the surface roughness, specific surface area, and pore volume of the biochar. Mercury porosimeter further confirmed a rise in BET specific surface area from 1.797 m²/g to 61.891 m²/g, and total pore volume from 0.7317 cm³ /g to 2.4921 cm³ /g. Using simulated blackwater as the research subject, a systematic investigation was conducted into the effects of PEI-BC dosage, pH value, adsorption time, and coexisting anions on the adsorption performance of Escherichia coli. Under optimal conditions, PEI-BC achieved a maximum logarithmic removal rate of approximately 4.84 log for Escherichia coli. The adsorption process closely followed pseudo-second-order kinetics and the Freundlich isotherm model. A combination of hydrogen bonding, electrostatic attraction, cation-π/π-π interactions, and physical pore entrapment governed the removal mechanism. This study presents a technical strategy utilizing modified biochar for the efficient removal of fecal coliform bacteria, providing a comprehensive analysis of its adsorption mechanism. • PEI-BC can efficiently absorb and remove fecal coliform bacteria from black water. • PEI-BC possesses a large pore volume and abundant adsorption sites. • The BBD method was used to optimise PEI-BC preparation to maximise its adsorption capacity for faecal coliform bacteria. • The PEI-BC adsorption process follows pseudo-second-order kinetics and the Freundlich adsorption isotherm model. • The key adsorption mechanisms of PEI-BC include electrostatic interactions, hydrogen and cation-π bonding, π-π interactions, and pore entrapment.