Effective sorption of toxic brilliant green using lignocellulosic waste biomasses and derived biochar samples

Abstract

Lignocellulosic waste biomass (LCW) certainly represents a part of the solutions to the lowcarbon future. LCW could serve as a base for a variety of sustainable fuels and bio based materials, whose proper implementation could help in economic and environmental growing world demands. Fruit stones, wastes from food processing industries, are contributing toward negative effects on the environment systems through the impacts associated with both waste production and its disposal. This waste type can be converted into value-added products using thermochemical methods, such as pyrolysis, where the biomass is efficiently converted into biofuels, biochars and different value added products. In this paper, two LCW materials, peach (PS) and cherry stones (CS) and their derived biochars (PS-B and CS-B), have been successfully applied for the removal of the hazardous water-soluble cationic dye, brilliant green (BG). Functional groups present in LCWs and related biochars were analysed using Fourier transform infra-red (FTIR) technique. Bio based sorbents were also characterized by determination of pHsus and pHpzc. The pristine LCWs, PS and CS, were first milled to desired dimensions, washed and dried at 60 oC. Pyrolysed samples, PS-B and PS-C, were obtained by heating in oxygen limited conditions from 25 to 500 оС (10 оС/min heat flow), and kept at 500 °C for 2 h. The contact pH (pHsus) as well as pHpzc were higher in both cases for the biochar samples, indicating higher –OH content (confirmed also by FTIR analysis) and favourable surface for cationic sorbate types. The experimental sorption results indicated that biochars have almost two times higher sorption capacities than the native materials, under the same operational conditions, while the highest binding was achieved by cherry stone biochar, 135.3 mg/g (experimental data modelled by Sips isotherm). Conclusively, the LCWs derived biochars can be efficiently used as an alternative to conventional sorbents in contaminated water treatment.