Optimization of Biochar Synthesis from Cosmetic Industry Sludge for Enhanced Removal of Enrofloxacin

Sewage sludge serves as a promising raw material for producing activated biochar (BC), offering both environmental and economic benefits. This work aimed to optimize the synthesis of biochar (BC) from cosmetic industry sludge using response surface methodology (RSM) with central composite rotational design (CCRD) and to assess its effectiveness in removing the antibiotic enrofloxacin (ENR) from synthetic effluents. The input variables considered were (i) residence time in the reactor and (ii) impregnation ratio (NaOH/biomass). The response for optimization was the iodine number. The sludge underwent pyrolysis at 550 °C under a nitrogen atmosphere. The optimized biochar (OBC) had a macroporous structure with a specific surface area of 46.1 m2 g–1 and a calorific value of 4146 kcal kg–1. The bio-oil contained nitrogenous compounds and alcohols. The effectiveness of the OBC in adsorbing ENR in aqueous systems was assessed. Kinetic assays showed an equilibrium time of 90 min, with the pseudo-second-order model best fitting the experimental data. The Langmuir isotherm model best described the adsorption (qmax = 15.83 mg g–1). The material is competitive with commercial adsorbents. This work underscores the potential of industrial sludges as a sustainable source for BC, contributing to pollution reduction and promoting circular economy practices.