Adsorption of Reactive Black-5 by Pine Needles Biochar Produced Via Catalytic and Non-catalytic Pyrolysis

Biomass derived biochar is increasingly recognized as an environmental-friendly sorbent to halt organic pollutants. This study explores the opportunity of managing pine needles waste by converting them into biochar sorbent through catalytic and non-catalytic pyrolysis, carried out at 450 °C. The difference in the biochar yield was not very obvious under catalytic and non-catalytic pyrolysis. The obtained biochars were characterized using X-ray diffraction analysis, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Adsorption of Reactive Black-5 (RB-5) in aqueous solution by produced biochar was studied. The effect of adsorbent dose in batch-mode experiments was investigated. The equilibrium adsorption data of RB-5 were analyzed by Langmuir and Freundlich models. Langmuir isotherms best described the adsorption data with higher correlation coefficient R2 values (R2 = 0.983, R2 = 0.995 and R2 = 0.941). The maximum RB-5 adsorption capacities qe(mg g−1) of elemental copper and cuprite (Cu–Cu2O)-based char, magnetite (Fe3O4)-based char and non-catalytically produced char from Langmuir model were 5.40, 2.82 and 4.37 mg g−1, respectively at 0.1 g adsorbent dose. These results indicated that the biochars are suitable to be used as an adsorbent for RB-5 removal.