Removal of pharmaceuticals and personal care products (PPCPs) from water by adsorption on aluminum pillared clay

The natural layered clay-based materials offer a sustainable approach for removal of emerging pollutants from the environment. Their low-capacity and poor-selectivity for pollutants often limit their uses. This limitation is addressed in this study with the help of Al-oxide pillaring approach. Here microporous aluminum-pillared clay (Al-PILC) was prepared from locally available Smectite clay (montmorillonite, MMT), by intercalation of Al-oxide pillars into the interlayer structure. The method increased the surface area of natural clay to 258 m2 g−1 and its porosity to 0.16 cm3 g−1. The adsorptive removal properties of prepared Al-PILC was evaluated on two selected pharmaceuticals and personal care products (PPCPs) viz. amoxicillin (AMOX) and imipramine (IMP). The results of the removal of these PPCPs were compared as a function of contact time (0–180 min), solution pH (2–12), initial concentration (0–100 mg L−1), and temperature (298–318 K). The Al-PILC adsorbs 332% more IMP and 681% more AMOX as compared to natural clay, and the maximum adsorption amounts on Al-PILC follows the order IMP > AMOX with 59.8 and 7.7 mg g−1, respectively. The kinetics of adsorption of both AMOX and IMP follow pseudo-second-order model, with intraparticle diffusion as rate-determining step. The incorporated acidic sites in clay (in form of Al2O3 pillars) enhanced its adsorption properties. These sites interacted with protonated amine and –OH groups of AMOX and the tertiary amine group of IMP. The Al-PILC exhibit effective regeneration and was reused up to three consecutive adsorption/desorption cycles. All in all, this study is expected to expand the application of Al-PILC on the adsorptive removal of the emerging pollutant from contaminated water.