Use of Larch, Spruce and Pine Cones as Unconventional Sorbents for Removal of Reactive Black 5 and Basic Red 46 Dyes from Aqueous Solutions

This study investigated the sorption properties of the biomass of larch (LaC), pine (PiC) and spruce cones (SpC) in relation to the anionic dye Reactive Black 5 (RB5) and cationic Basic Red 46 (BR46). The scope of the study included the properties of the sorbents (FTIR, SSA, fiber content, elemental analysis C, N, H, pH_PZC), the effect of pH on the sorption efficiency of the dyes, the sorption kinetics (pseudo-first-order model, second-order model, intraparticle diffusion model) and the maximum sorption capacity of the sorbents (Langmuir 1 and 2 models, Freundlich). The sorption efficiency of RB5 on the sorbents tested was highest at pH 2 and BR46 at pH 6. The pH_PZC values determined for LaC, PiC and SpC were 6.86, 7.02 and 7.19, respectively. The sorption equilibrium time depended mainly on the initial dye concentration and ranged from 150 to 180 min for RB5 and from 120 to 210 min for BR46. The sorption capacities (Q_max) of LaC, PiC and SpC for RB5 were 1.05 mg/g, 1.12 mg/g and 1.61 mg/g, respectively, and for BR46 were 70.53 mg/g, 76.60 mg/g and 96.44 mg/g, respectively. The most efficient sorbent for both dyes was SpC, which was partly related to the high lignin content of the material.