Development of zeolite from steelmaking slag to effectively remove Pb(II) ions in an aqueous environment: experimental and theoretical study

The study highlights that zeolite produced from steel slag effectively eliminates Pb(II) ions from aqueous solutions in batch experiments, as evidenced by comprehensive tests examining multiple variables, including contact time, adsorbent quantity, stirring velocity, pH levels, temperature conditions, particle dimensions of the adsorbent, and initial concentration of the solute. Experimental investigations have demonstrated that steel slag can be effectively converted into zeolite via chemical and thermal processing methods, yielding a material abundant in silica, alumina, and sodium oxide, with a specific surface area of 416 m 2 /g. The analytical monitoring of lead removal has highlighted the crucial role of key parameters, allowing us to reach a maximum adsorption capacity of 124.08 mg/g after a 40-minute contact period. The analysis of adsorption isotherms showed that the process takes place on a homogeneous, uniform monolayer. The separation factor (R L ) and the heterogeneity factor (1/n) both confirmed the favorable characteristics of the process. Furthermore, the heterogeneity factor (1/n) and the average energy (E) indicated that lead elimination occurred predominantly via physical adsorption mechanisms. The results of the kinetic analysis of adsorption showed that the lead elimination process followed pseudo-second-order kinetics, which depended on both external and internal diffusion. From a thermodynamic perspective, the process carried out proved to be exothermic, spontaneous, and less entropic. The free energy, enthalpy, and activation energy reaffirmed that it was a physical adsorption. The desorption process demonstrated that the zeolite retained its initial adsorption capacity after five cycles, ranging from 91.68 to 99.88% using hydrochloric acid as a solvent.