Improvement of adsorption of sulfadiazine on tannic acid–chitosan biochar by nickel doping through a polyphenol metal network

Antibiotics, as a representative of new pollutants, have always been a challenge in the water treatment process, and most adsorption materials do not have good adsorption capacity for them. Therefore, the adsorption capacity of materials for antibiotics was investigated using sulfadiazine (SDZ) as a representative of antibiotics. In this paper, nickel was successfully loaded onto the surface of chitosan through a polyphenol metal network. TAB-Ni was prepared by adding an appropriate amount of tannic acid-chitosan material to 0.03 mol L^-1 nickel chloride under alkaline conditions, and then calcined at a high temperature of 900 °C for 2 hours. The morphology and functional groups on the material surface were determined using a series of characterization methods, and the adsorption behavior of SDZ on TAB-Ni and the stability of the material were also evaluated. The results show that TAB-Ni has a strong adsorption capacity for SDZ, reaching 123.89 mg g^-1 at 298 K and 152.56 mg g^-1 at 318 K, exceeding the adsorption capacity of most carbon materials. Most importantly, the graphitization of nickel-doped biochar enhances the role of biochar in the adsorption mechanism and dramatically improves the affinity (π-π interactions) between the aromatic structure and the benzene ring in the SDZ molecule and can provide metal-unsaturated sites to enhance the adsorption capacity for SDZ. The present study sheds light on the enhanced adsorption of SDZ by carbon materials in the future.