Enhancing zinc(II) removal from Sulaymaniyah industrial zone sewage using novel adsorbents: a comprehensive study of natural clay, acid/base activated clay, and titanium pillared clay: insights into kinetics and thermodynamics

The local natural clay from Darbandikhan (DC) was evaluated as a possible adsorbent for the adsorption of Zn 2+ in its natural state, after [acid activation (ADC), base activation (BDC), and after pillaring (TiPDC)] in the laboratory and Sulaimani city industrial zone sewage. X-ray Diffraction, X-ray Fluorescence (XRF), Fourier-Transform Infrared Spectroscopy, Thermal gravimetric analyses, and N 2 physisorption analyses were used to study the effects of different clay treatments on the surface, and adsorptive properties of the clay. The modifications resulted mainly in the removal of the calcite content and a significant increase in the surface area from 24.38 to 30.65, 32.19, and 47.46 m 2 g −1 for DC, ADC, BDC, and TiPDC respectively. The adsorbent materials were examined for their efficiency to remove Zn 2+ contaminant from Sulaimani industrial zone sewage by a batch method. ADC and TiPDC presented more than 99.9% removal (from 308.0 to less than 0.01 μg/L) of Zn 2+ . The estimated kinetic parameters illustrate that there is a directly proportional between the adsorption capacity and temperature for Zn2 + ions adsorption by DC, ADC, BDC, and TiPDC. The thermodynamic study showed that the adsorption of Zn 2+ was found to be spontaneous above 20 °C for adsorbent (∆G° = -ve), and endothermic (∆H° = + ve) with an increase in the randomness at the adsorbate-adsorbent contact layer (∆S° = + ve). The natural clay and the modified materials (ADC, BDC, and TiPDC) can be regarded as good adsorbents for removing Zn 2+ from wastewater. Graphical abstract