Adsorption-degradation of malachite green using alkali-modified biochar immobilized laccase under multi-methods

[Display omitted] •Laccase was immobilized onto A-MB via multi-immobilization methods.•The adsorption of MG on A-MB followed the pseudo-second-order equation.•The adsorption of MG on A-MB followed the Langmuir isotherm model.•A-MB possessed a relatively high qmax (757.58 mg/g) for MG.•The maximum removal rate of immobilized laccases was high than 97.70 %. Malachite green (MG) is an environmental persistent pollutant. The excellent adsorption capacity and enzyme carrier potential of alkali modified biochar (A-MB) are potential solutions for the treatment of MG. In this paper, laccase was immobilized onto A-MB via multi-immobilization methods. The batch adsorption equilibrium experiments were conducted to study the adsorption behavior of MG on carrier A-MB. The results showed that the adsorption of MG on A-MB followed the pseudo-second-order equation and the Langmuir isotherm model. In addition, A-MB possessed a relatively high qmax (757.58 mg/g) for MG. The comparative experiment was set up to compare the removal rate of MG on free laccase (FL) and immobilized laccase (adsorption method: A/lac@A-MB; adsorption-crosslinking method: A-C/lac@A-MB; covalent binding method: CB/lac@A-MB), the maximum removal rate of FL was 89.68 %, but the maximum removal rate of A/lac@A-MB, A-C/lac@A-MB and CB/lac@A-MB was 97.70 %, 98.77 % and 97.86 %, respectively.