Adsorption of Organic and Inorganic Pollutants from Wastewater Using Various Effective Adsorbents: A Comparative Study

Abstract

In this study, a variety of novel binary and tertiary nanocomposite materials were synthesized starting from graphene oxide (GO), MgFeAl layered triple hydroxide (LTH), and bentonite (BT). The synthesized binary and tertiary nanocomposites, along with their parental materials, were characterized using various techniques (i.e., BET, XRD, FTIR, SEM/EDS, Boehm titration, and zeta potential) before assessing their efficacy in removing eight detrimental water pollutants, namely, crystal violet (CV), methylene blue (MB), methyl orange (MO), acid red 1 (AR1), 2-nitrophenol (2NP), bisphenol A (BPA), lead (Pb(II)), and chromium (Cr(VI)) from wastewater samples. The results indicated that the nanocomposites formed from GO and BT (referred to as GO/BT) is particularly effective in removing MB while the one formed from LTH, polyethyleneimine (PEI)-functionalized GO (abbreviated as FGO), and BT (referred to as LTH/FGO/BT) is more superior in removing CV. On the other hand, the calcined LTH (abbreviated as C-LTH) proved to be the most efficient adsorbent for removing both MO and AR1. For phenolic pollutants, the nanocomposites formed from LTH, GO, and BT (referred to as LTH/GO/BT) and the one produced from C-LTH and BT (referred to as C-LTH/BT) are the most effective in removing 2NP and BPA, respectively. Furthermore, pristine LTH and the nanocomposite of LTH and BT (referred to as LTH/BT) emerged as the top performers for adsorbing Pb(II) and Cr(VI) from synthetic wastewater. These results provide a practical selection map that connects pollutant class to optimal sorbent chemistry. Kinetic analysis (done for selected systems) showed that the pseudo-second-order model reproduces the full-time course more accurately than the pseudo-first-order model, consistent with fast early uptake followed by a slower approach to equilibrium. Reusability tests highlighted the importance of regeneration: without washing, removal by C-LTH and by LTH/GO/BT dropped from 94.4 and 97.0% to about 57.4 and 62.2% by the third cycle; a simple NaOH rinse restored most capacity in the composite, maintaining about 97, 94.4, and 88.8% removal over three cycles. Together, the data show that no single material maximizes removal across all pollutants, but rational pairing of pollutant chemistry with sorbent acidity, basicity, and other properties could deliver high adsorption capacities and regenerable performance.