Competitive Adsorption of Neutral Red and Cu2+ onto Pyrolytic Char: Isotherm and Kinetic Study

Pyrolytic char treated with muffle furnace (TPC) was used as an adsorbent for the removal of neutral red (NR) and Cu 2+ from aqueous solutions in a batch system. The adsorption behavior of NR and Cu 2+ in single and binary systems on the TPC was studied. For a single system, the NR and Cu 2+ adsorption isotherm followed Langmuir and Redlich–Peterson models with a maximum adsorption capacity of (0.216 and 0.261) mmol·g –1, respectively. The adsorption kinetics of NR and Cu 2+ followed both the pseudosecond-order and Elovich equations. The diffusion process with two stages for NR and Cu 2+ can describe the adsorption process. For a binary system, NR and Cu 2+ showed competitive adsorption on the TPC. The adsorption isotherm of NR and Cu 2+ still followed the Langmuir model, and the adsorption kinetic models of NR and Cu 2+ still followed the pseudosecond-order kinetic model, while the diffusion process of NR was single-stage and two-stage for Cu 2+ . The adsorption capacity of NR and Cu 2+ is reduced compared with that in a single system, but the total adsorption capacity is higher. TPC has a higher affinity toward Cu 2+ over NR.