Abstract
AbstractNatural bentonite clay (NBC) was activated using nitric acid (HNO3). Characterization techniques including FTIR, SEM, XRD and BET were employed to examine the morphology of NBC and ABC (activated bentonite clay) sorbents. Comparative application of ABC and NBC to remove heavy metals (Fe2+, Zn2+, Ni2+) from pharmaceutical effluents was investigated under various experimental conditions. The maximum proportional removal by ABC was 88.90, 81.80 and 75.50% at pH 8, and 63.90, 59.60, 58.70% at pH 10 for NBC, both for Zn2+, Fe2+ and Ni2+ respectively. The Freundlich multilayer adsorption model and pseudo-second-order kinetics best fit the experimental data, suggesting the formation of multiple adsorption layers via strong ionic and electrostatic interactions. Heavy metals adsorption is more favorable with ABC than NBC, due to the availability of more sorption sites and a larger specific surface. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) revealed that the adsorption is endothermic and spontaneous in nature for both ABC and NBC.
Highlights
Metal pollution of surface waters is often due to indiscriminate discharge of the metals or wastewater containing them metals into watercourses (Ahmetović et al 2019)
scanning electron microscopy (SEM) micrographs The effect of acid activation on the adsorbent surfaces is reflected in the SEM micrographs – Figure 1(a) and 1(b). the ABC surface clearly has relatively larger particles than Natural bentonite clay (NBC), which appears to be compact with irregularly shaped particles
The results show that, as the wastewater pH increases in the presence of ABC and NBC, the amounts of the heavy metals adsorbed increase due to electrostatic attraction
Summary
Metal pollution of surface waters is often due to indiscriminate discharge of the metals or wastewater containing them metals into watercourses (Ahmetović et al 2019). Heavy metals are hazardous to humans and aquatic fauna due to their poor degradability, biomagnification tendencies, and the toxicity of high concentrations (Ore & Adeola 2021). These hazards necessitate legislation against the direct discharge of heavy metals into the environment. The distinct physicochemical properties of bentonite – e.g., low permeability, low cost, strong absorptive affinity with inorganic and organic substances, large specific surface, small particle size, high porosity, and high cation exchange capacity – make it an effective adsorbent of different kinds of pollutants (Uddin 2017)
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