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In this study, the feasibility of utilizing Acacia tortilis biomass for the removal of cadmium ions was investigated. The effect of operating parameters, namely, initial pH (1-10), cadmium concentration (50-200 mg/L), biosorbent dose (0.5-4.0 g/L), and agitation speed (0-400 rpm), on the cadmium removal was investigated. Maximum removal efficiency was attained at pH 5.0, at an equilibrium time of 180 min. The maximum cadmium uptake achieved with 200 mg/L initial concentration was 36.66 mg/g. The mechanism of biosorption was analyzed using the pseudo-first-order, pseudosecond-order, and intraparticle diffusion models. The pseudo-first-order model represented the data well (R 2 > 0.993), and the maximum uptake capacity was 45.83 mg/g at 30 • C with 200 mg/L manganese concentration. Desorption studies confirmed the suitability of sulfuric acid as an eluent producing recoveries in excess of 90% for cadmium up to four cycles.

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In this experimental study, a novel biosorbent was synthesized from Anogeissus dhofarica and applied for defluoridation under batch-shaking conditions. The influence of process variables, namely initial pH (3.0–11.0), fluoride concentration (50–200 mg/L), biosorbent dosage (0.25–8.0 g/L) and agitation speed (0–600 rpm), on the fluoride uptake was studied. Fluoride uptakes increased with increase in fluoride concentration due to enhanced driving force and decreased with increase in biosorbent dose. An empirical relationship, exponential in nature, was proposed between fluoride uptake and biosorbent dose. The pseudo-second-order rate constant (k2) was determined as 0.00474 g/ (mg.min) at 303 K with an initial fluoride concentration of 100 mg/L and the rate constant increased with increase in temperature. The activation energy was determined as 6.023 kJ/mol. The chemisorptive nature of fluoride removal was proven through kinetic modeling. The findings of this research proved the feasibility of industrial application of this novel biosorbent for fluoride removal over a wide range of environmental conditions.