Enhanced adsorption performance of phosphoric acid activated biochar from in-situ pre-carbonized bamboo shoot shells

As a kind of renewable resource, bamboo resources play an important role in achieving carbon neutrality goals. However, it is estimated that 17.64 ∼ 22.05 million tons of bamboo shoot shells (BSS) are discarded every year in China, which causes serious environmental pollution and waste of resources. Activated carbon was prepared via phosphoric acid treatment using pre-carbonized bamboo shoot shells (PBSS) made in a mobile carbonization kiln as raw material. Using PBSS with a particle size range of 20–40 mesh after washing pretreatment as carbon precursor, the corresponding activated carbon (WAC-20/40) with superior adsorption properties for the removal of methylene blue (MB) was prepared under the optimized activation conditions of phosphoric acid mass fraction of 70 %, activation temperature and time of 600 ℃ and 80 min. Furthermore, under the appropriate adsorption conditions, the adsorption capacity and adsorption rate of MB are as high as 344.51 mg/g and 97.04 %, respectively, which could remain above 77 % after four runs, highlighting a good reusability of WAC-20/40. The adsorption process follows pseudo-second-order adsorption kinetic model and Langmuir isothermal adsorption model. In a case of WAC-20/40 dosage of 4 g/L, the reduction rate of content of chemical oxygen demand in the industrial wastewater of a pickled bamboo shoots’ food factory was up to 91.51 %, exhibiting a superior adsorption performance of WAC-20/40 and its potential industrial application prospects in the field of wastewater treatment. • In-situ pre-carbonization is conducive to the cost-effective utilization of BSS. • The ash content of PBSS is reduced by 60.57 % after screening and water-washing. • The result of pH effect on MB adsorption is reliable via calibrating working curve. • The adsorption capacity of WAC-20/40 for MB removal can be up to 630.79 mg/g. • The reduction rate of COD content in wastewater is 91.51 % after WAC-20/40 adsorption.