Sintered poultry-base waste as low-cost adsorbent for the uptake of Congo red: insight into kinetics, isotherms and thermodynamics

The presence of dyes in wastewater constitutes environmental pollution which pose severe concern to not only human existence but also the entire eco-systems requiring urgent and effective treatment techniques. This research investigates the valorization of poultry-based waste as a sustainable and low-cost adsorbent for the uptake of Congo red (CR) dye from aqueous solutions. Poultry-based waste was thermally treated through sintering at 650 °C to form sintered poultry-based waste (SPBW), and its adsorption performance was compared with that of untreated poultry-based waste (PBW). Comprehensive characterization with SEM, FT-IR, XRD, BET, pHₚzc, and TGA indicated that sintering greatly improved the pore structure, surface properties, functional group stability, and adsorption site accessibility. Adsorption equilibrium was achieved within 120 min and 100 min for SPBW and PBW at a pH of 4.0 and 2.0, with SPBW exhibiting superior adsorption capacity and stability compare with PBW. Kinetic data reveal that CR uptake onto PBW and SPBW followed the pseudo-first-order model. Data from equilibrium investigation confirmed Langmuir fitted well with PBW, while Freundlich fitted well the SPBW. PBW and SPBW showed maximum monolayer adsorption capacities of 40.16 mg g−1and 60.23 mg g⁻¹ respectively. Thermodynamic determinations confirmed that the adsorption process was spontaneous and endothermic, with ΔH° values of 16.93 kJ/mol for PBW and 32.55 kJ/mol for SPBW. Desorption studies showed good regeneration potential over multiple cycles, most especially for SPBW. In all, the results demonstrate that sintered poultry-based waste is an efficient, environmentally sustainable, and reusable adsorbent for anionic dye removal from wastewater.