Effect of nickel salts on the production of biochar derived from alkali lignin: properties and applications

The massive generation of alkali lignin, has aroused the attention of all walks of life, and an eco-friendly utilization approach needs to be exploited. Herein, a simple pretreatment method with nickel salts was developed for the valorisation of alkali lignin through slow pyrolysis. The pretreatment of nickel salts improved the foaming or swelling behaviors of alkali lignin upon heating, and the specific surface area and total pore size of biochars increased about thirteenfold and eighteenfold, respectively. Additionally, Ni-0 particles were generated and embedded in the carbon matrix of biochars. The biochar from Ni(NO3)(2) pretreated lignin catalyzed the selective hydrogenation of nitrobenzene, yielding 80.5% of aniline; and that from (CH3COO)(2)Ni pretreated lignin showed adsorption capacity of lead around 87.1 mg/g. Moreover, the NiCl2 pretreatment contributed to the formation of 1,2-dihydroxybenzene, while Ni(SO4)(2) was conducive to the production of 4-methylguaiacol.

Automated summary

The pretreatment with nickel salts significantly improved the thermal behaviors and characteristics of alkali lignin during slow pyrolysis, resulting in biochars with increased specific surface area and pore size. The biochars catalyzed selective hydrogenation of nitrobenzene and demonstrated high adsorption capacity for lead, with different nickel salts contributing to specific product formations.