Adsorption of p-chlorophenol and p-nitrophenol in single and binary systems from solution using magnetic activated carbon

Abstract

Magnetic activated carbon (MAC) was prepared by co-precipitation. These particles had attractive adsorption capacity and could be easily separated from aqueous. MAC was used as adsorbent to remove p-chlorophenol (p-CP) and p-nitrophenol (p-NP) from solution in single and binary systems. In a single system, the equilibrium time was 60 min, the best initial pH was 3-8 and 3-6 for p-CP or p-NP adsorption, respectively. The existence of salt ions had little influence on the adsorption process, while surfactant had negative influence. The adsorption quantity from experiments was up to 97.3 mg·g−1 for p-CP and 116 mg·g−1 for p-NP at 293 K, respectively. Freundlich model and pseudo-second-order kinetic model fitted well the adsorption behavior. Thermodynamic parameters were calculated and the results showed that the process was spontaneous, exothermic and entropy production in nature. In addition, p-CP or p-NP-loaded MAC could be well reused by 0.01 mol·L−1 sodium hydroxide solution as regeneration agent. Kinetic process of desorption was fitted best by pseudo-second-order kinetic model. Results from the binary system showed that competitive adsorption existed during the process, and p-NP adsorption on MAC was easier than p-CP. Freundlich model well fitted the adsorption behavior in the binary system. Hydrogen-bonding, electron donor-acceptor and π-π interactions may be the main mechanisms of adsorption. MAC proved to be an excellent adsorbent for the removal of p-CP and p-NP from solution.