Utilization of lignin separated from pre-hydrolysis liquor via horseradish peroxidase modification as an adsorbent for methylene blue removal from aqueous solution

The lignin in PHL could be modified and recovered from pre-hydrolysis liquor (PHL) by horseradish peroxidase (HRP) treatment. The enzyme-modified lignin (EML) separated from PHL was used to adsorb and remove methylene blue (MB) from a model dye effluent; the adsorption performance of EML was studied. The results indicated the carboxyl content of the lignin in PHL increased by HRP treatment, and the EML removed from PHL had a carboxyl content of 0.69 mmol/g and a BET surface area of 25.6 m2/g. With the increase of pH, the adsorption capacity of EML obviously increased. The maximum MB adsorption capacity of EML was 210.2 mg/g and 241.1 mg/g at 298 K and 308 K, respectively. The fitting results revealed that the equilibrium adsorption isotherms and adsorption kinetics followed the Langmuir model and pseudo-second-order model, respectively.

Automated summary

The carboxyl content of lignin in PHL increased by HRP treatment, resulting in higher adsorption capacity of the extracted EML. The adsorption capacity of EML increased significantly with the increase of pH.