Peach stone biochar as efficient adsorbent for Cd(II) removal from aqueous phase

Abstract

Lignocellulosic waste biomass (LCW) represents valuable resource whose implementation could help growing world demands in improving environmental problems. Fruit stones, as waste from food processing industry, are contributing toward negative stresses on our natural systems through impacts associated with both waste production and its disposal. Sustainable waste management practice necessitates that industries must shift from the current linear model to a circular based economy, utilizing wastes generated as initial materials for the production of new products, such as fuels, chemicals or materials which might help in solving environmental pollution topics. Waste biomass materials can be converted into value-added products using thermochemical methods, such as pyrolysis, whereby biomass is efficiently converted into biofuels, biochars and different value added products. This paper present current development work and evaluates potential opportunities for food processing waste pyrolysis focusing on the conversion of peach stones (PS) to biochar. The wasted PS were first crushed, milled to desired dimensions and then pyrolysed, heating from 25 to 500 оС at 10 оС/min heat flow, and kept at 500 °C for 2 h. The resulting biochar (PS-B) was characterized to determine the potential of this products for Cd(II) sorption as well as to distinguish sorption kinetics of Cd removal between raw and pyrolysed material. Kinetic experiments were performed in isothermal batch system with mixing (200 rpm), at 25 oC, adding 0.1g of sorbent in 50 ml of Cd(II) solution, with initial Cd concentration of 100 mg/L. Experimental results were modelled with three kinetics (pseudo-first, pseudo-second order and Elovich equation) and one diffusion model (Weber-Morris). Results of kinetic modelling indicated chemisorption mechanism with different diffusional behaviour of the samples. The contact pH (pHsus) of these materials were 4.10 (PS) and 5.76 (PS-B), indicating higher –OH content in biochars, which was also confirmed by FTIR analysis. The experimental results indicated that PS-B has almost five times higher sorption capacity than the native material (PS), under the same operational conditions, 24.50 mg/g compared to 5.25 mg/g, respectively. Conclusively, the PS derived biochar can be used as an alternative to conventional sorbents in contaminated water treatment. Moreover, more research work needs to be conducted on this waste type to biochar in order to investigate optimal operational parameters as well as flow system behaviour.