Facile construction of cationic lignin modified bentonite–alginate nanocomposite gel for sustained release of alachlor

In our work, a cationic lignin (CL) modified bentonite‐alginate nanocomposite gel was prepared and used to enhance the sustained release of alachlor. The underlying gel structure‐release property relationships were explored. The results showed that the release of alachlor from nanocomposite gel was dominated by Fickian diffusion and closely related to the adsorption capacity and permeability of the matrix. The adsorption capacity of bentonite for alachlor was remarkably improved due to the modification of CL; Furthermore, the permeability of the matrix was further reduced via the electrostatic interaction between CL and the alginate. The release kinetics demonstrated that the sustained release property of modified bentonite‐alginate nanocomposite gels was significantly enhanced. The release time of 50% alachlor from bentonite‐alginate and modified bentonite‐alginate nanocomposite gels was 4.4 and 14.1 times longer than that of the release from pure alginate gel, respectively. The cationic lignin was prepared by the etherification reaction of lignin and used to modify bentonite by ion exchange. After modified with cationic lignin, the hydrophobicity and the adsorption capacity of bentonite for alachlor had been remarkably enhanced. Meanwhile, the electrostatic attraction between cationic lignin and alginate made bentonite better dispersed in alginate gel and significantly reduced the permeability of alginate gel. Finally, the modified bentonite‐alginate nanocomposite gel obtained better sustained release property.