Biochar produced from the co-pyrolysis of sewage sludge and waste tires for cadmium and tetracycline adsorption from water

Abstract

Application of sewage sludge biochar as an adsorbent for pollutant removal has obtained special attention due to their low cost and surface functionality. In this research, sludge–tire composite biochar (STB) was successfully prepared through co-pyrolysis at 300, 500 and 700 °C, respectively. Cadmium (Cd) and tetracycline (TC) were selected as the target pollutant. The results indicated that STB has the highest surface area (49.71 m2/g), more inorganic minerals (Kaolinite) as well as relatively stable physicochemical properties with 10% tire particles (TP) at 700 °C. The adsorption results indicated that the pseudo-second-order equation and Langmuir isotherm model could better describe the adsorption of Cd2+ and TC by STB. The maximum adsorption capacity of Cd2+ and TC was 50.25 mg/g and 90.09 mg/g, respectively. The main mechanism of the adsorption process of STB for Cd mainly involves anion binding adsorption and ion exchange. The main mechanism of the adsorption process of STB for TC mainly involves complexation and cation exchange. The present study could set a scientific foundation for further research on the recycle of sewage sludge and tires. HIGHLIGHTS 700 °C was demonstrated to be the best pyrolysis temperature, 10% is the optimal blending ratio of TP.; The blending of TP can reduce the risk of adsorbate being discharged from biochar into the environment.; Combining with anion and ion exchange are possible ways for STB to remove Cd2+.; Complexation and the cation exchange are possible ways for STB to remove TC.;

Keywords

• adsorption
• biochar
• cadmium
• sewage sludge
• tetracycline
• waste tires