Adsorption behaviors and mechanisms of simultaneous cadmium and fluoride removal on waste bovine bone from aqueous solution

Abstract

Cadmium (Cd2+) and fluoride (F-) are frequently detected simultaneously in wastewater. Simultaneous removal of Cd2+ and F- in wastewater is urgent. In this study, bovine bone meal (BBM), mainly consisted of hydroxyapatite, was used as a green adsorbent for Cd2+ and F- adsorption in single and binary solutions. The results showed that with the increase of pH, the uptake ability of BBM towards Cd2+ and F- showed an upward and downward trend, respectively, suggesting that electrostatic interaction was an important mechanism. Cl- and NO3- had little effect on Cd2+ and F- adsorption, while H2PO4- enhanced adsorption capacities. The kinetic data of Cd2+ and F- removal were successfully described by pseudo-second order model. The maximum adsorption capacity (qm) of Cd2+ obtained from the Langmuir model was 78.969 mg/g. The adsorption isotherm of F- was consistent with S-type and satisfied with the Brunauer, Emmett, and Teller (BET) model. In the binary system, F- slightly decreased the adsorption capacity of BBM on Cd2+, while Cd2+ increased the adsorption capacity of BBM on high-concentration F- from 38.724 to 86.966 mg/g. This study provides a cost-effective and environmentally friendly method for separate and simultaneous removals of Cd2+ and F- from water, which provides a practicable way for the treatment of cadmium-fluorine wastewater and resource utilization of bovine bone.