Eco-friendly, renewable Crambe abyssinica Hochst-based adsorbents remove high quantities of Zn 2+ in water

Although not considered poisonous and with natural occurrence, Zn contamination is mainly related to anthropic actions. This research aim was to develop, from crambe wastes, adsorbents with high adsorption capacity of Zn2+. The crambe biomass was modified with H2O2, H2SO4 and NaOH 0.1 mol L−1, resulting in four crambe-based adsorbents: C. in natura (unmodified), C. H2O2, C. H2SO4 and C. NaOH. These were studied by determination of their chemical components, SEM, FTIR, pHPZC, thermal stability (by TG/DTG curves), SSA, pore volume and pore diameter (by BET and BJH). Adsorption studies were also carried out to evaluate its Zn removal capacity. Evaluations were taken on adsorbent dose and the influence of the pH, as well as studies on adsorption kinetics and equilibrium. These results were evaluated by pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion, Langmuir, Freundlich, Dubinin-Radushkevich and Sips (linear and nonlinear models). Results show that the crambe-based adsorbents may have functional groups such as hydroxyls, amides, carbonyls and carboxylates, which may be responsible for the Zn2+adsorption. The materials have heterogeneous structure, allowing the occurrence of mono and multilayer adsorption of Zn. The finest results point out the occurrence of mono and multilayer of Zn2+ (evidenced by Sips-nonlinear model), with an increase in Qsat of 72% (C. H2O2), 22% (C. H2SO4) and 80% (C. NaOH). The developed crambe adsorbents have low cost of production (since the raw material is until now a solid waste) and have high removal ratio of Zn2+ from waters, being a promising technology.