Biochar from lignocellulosic waste as a sustainable alternative to anthracite carbon in water treatment

Peanut shell samples were collected, submitted to simulation of torrefaction conditions by thermogravimetric analysis to assess its decomposition, stability and thus obtain parameters such as heating and resident temperature to produce biochar. A stability test in an aqueous medium was conducted to determine the optimal temperature for biochar production which indicated that a temperature of 280∘C was the most suitable. The biochar obtained was separated into fractions of 1 mm and 2 mm of granulometry, namely, CA1MM and CA2MM. These same conditions were applied to urban pruning biomass to produce CP1MM and CP2MM. All the biochars produced were compared to anthracite charcoal. Due to low column flow, the biochars with 1 mm were excluded from the following tests. CA2MM and CP2MM presented pH 7.34 and 6.98, zero charge point (ZCP) 4.63 and 6.39, apparent density 0.13 g cm3 and 0.17 g cm3, flow rate of 22.37 L h-1 and 13.88 L h-1 in column, COD effluent 18 mg L-1 and 11 mg L-1, iodine number of 187.60 mg g-1 and 247.59 mg g-1, and maximum adsorption capacity of methylene blue Qe 8.17 mg g-1 and 10.6 mg g-1, respectively. Anthracite charcoal CANT showed ZCP 4.60 and iodine number of 202.61 mg g-2 and Qe 11.3 mg g-1. The produced biochars and charcoal showed physisorption through Freundlich isotherm and adsorption on the monolayer according to the Langmuir isotherm classifying them as reusable. The elemental analysis and infrared spectra indicated the presence of negatively charged groups. According to the results, the CA2MM and CP2MM biochars can be used as a substitute for charcoal in water filtration in a water treatment and as a viable solution for the reuse of these residues.