Preparation of an alternative adsorbent from Acacia Mearnsii wastes through acetosolv method and its application for dye removal

A new, low cost and alternative adsorbent was prepared from black acacia bark wastes by acetosolv treatment, which consists in the use of organic solvents and inorganic acids. Both materials, black acacia bark (BAB) and acetosolv treated black acacia bark (BAB–AT) were characterized in detail and used to remove crystal violet dye (CV) from aqueous media. Adsorption parameters like pH, adsorbent dosage, kinetic, equilibrium, thermodynamics and ionic strength were evaluated to determine the efficacy and, the best conditions for CV removal. The characterization showed than the most important changes occurred in lignin portion of the material, resulting in many functional groups on the BAB–AT surface. BAB–AT presented superior potential in relation BAB, reaching removal percentages of 95%, with adsorbent dosage of 750 mg L−1 and pH of 10. Homogeneous solid diffusion model (HSDM) was able to explain the kinetic profile. The equilibrium was attained within 2 h and the intraparticle diffusion coefficients were from 10−12 to 10−8 cm2 s−1. The equilibrium was well represented by the Freundlich model. Maximum adsorption capacity was 280 mg g−1. The adsorption process was spontaneous favorable and endothermic. In summary, the acetosolv treatment is a promising alternative to transform black acacia bark wastes in and efficient adsorbent (BAB–AT), thus aggregating value to this material. BAB–AT in turn is a low cost and efficient material which can be used to treat colored effluents.