Mechanistic investigation of Pb adsorption on biochar modified with sodium alginate composite zeolitic imidazolate framework-8.

For the serious situation of heavy metal pollution, the use of cheap, clean, and efficient biochar to immobilize heavy metals is a good treatment method. In this paper, SA@ZIF-8/BC was prepared for the adsorption of Pb in solution using sodium alginate (SA) and zeolitic imidazolate framework-8 (ZIF-8) modified corn cob biochar. The results showed that the specific surface area of modified biochar was greatly improved, with good adsorption capacity for Pb, strong anti-interference ability, and good economy. At the optimal adsorption pH of 5, the adsorption model of Pb by SA@ZIF-8/BC was more consistent with the pseudo-second-order kinetic model and Langmuir isotherm model. This indicates that the adsorption of Pb by SA@ZIF-8/BC is chemisorption and monolayer adsorption. The maximum adsorption of modified biochar was 300 mg g, which was 2.38 times higher than that of before modified BC (126 mg g). The shift in binding energy of functional groups before and after adsorption of SA@ZIF-8/BC was studied by XPS, and it was found that hydroxyl and carboxyl groups played an important role in the adsorption of Pb. It was demonstrated that this novel adsorbent can be effectively used for the treatment of Pb pollution in wastewater.