Cation‐assisted adsorption of chlorophenols by nano‐xerogels

Abstract

With water quality deteriorating globally, identification of novel adsorbents for removal of chloroaromatic compounds for wastewater treatment is of growing interest. Classic xerogels produced by drying sol-gels of tetraalkoxy silanes, such as tetramethoxy orthosilane (TMOS) or tetraethoxy orthosilane (TEOS), carry a negative surface charge in water when the pH is higher than the Point of Zero Charge (PZC). This feature was employed in this study to load divalent metal cations on the surfaces of these materials to facilitate chlorophenol (CP) adsorption. Although classic xerogels do not show a high affinity for the adsorption of chlorophenols such as 2-chlorophenol (2CP) in aqueous media, TEOS xerogels loaded with the cations Ni 2þ , Cd 2þ , and Zn 2þ showed 225, 249, and 306 % increases, respectively, in the adsorption of 2CP compared to the unloaded TEOS xerogel. Adsorption of the divalent cations on the xerogels exhibited the order of Zn 2þ > Cd 2þ > Ni 2þ , with maximum adsorption capacities (Q8) of 15.9 and 13 mg/g for Zn 2þ on TEOS and TMOS xerogels, respectively. Using TEOS xerogels loaded with Zn 2þ (TEOS-Zn), adsorption of 2CP, 2,4-dichlorophenol (DCP), and 2,4,6-trichlorophenol (TCP) in aqueous media was studied. The adsorption was found to be spontaneous and obeyed pseudo-second order kinetics, suggesting a chemisorption mechanism between CP and TEOS-Zn. The equilibrium isothermal adsorption data were most closely fitted with a Langmuir equation resulting in Q8 values of 13.9, 9.17, and 8.5 mg/g for 2CP, DCP, and TCP, respectively.

Application of SD/MNP/PEI Nanocomposite for Heavy Metals Sorption

“…The straight line plots of ( ) ln et qqagainst t were used to determine the rate constant, 1 k and correlation coefficient, 2 R , values of the lead were calculated from this plot. 32,44…”

Comparison Study of Paraquat Herbicide Adsorption by Xerogels: Application of Experimental Design

“…Silica‐based materials were used for different adsorption applications frequently, due to their physical, chemical and mechanical properties . The xerogels are strong, low‐priced, non‐toxic, and capable of recycling.…”

“…Therefore, adsorption of PQT on TEOS and TMOS xerogels is electrostatically possible. Haghbeen et al used hybrid xerogels for the removal of phenolic compounds and cation assisted xerogels and nano‐porous xerogel for the removal of metal ions.…”

“…According to the above‐mentioned points, it is essential to improve the procedural conditions, minimize the working cost, and maximize the adsorption performance and removal efficiency. The adsorption performance of xerogel for metal ion was improved using the traditional one‐factor‐at‐a‐time method . To find the combined effects of all factors, a classical method that fixes one factor and involves others is imperfect.…”