Removal of naphthalene utilizing synthesized silica doped PVA aerogel: removal, optimization and mechanism

Abstract The focus of this study is the modification of (3-Aminopropyl) triethoxysilane (APTES) by hydrogen peroxide (H 2 O 2 ) and its utilisation as a filler in Polyvinyl alcohol (PVA) aerogel preparation along with normal APTES and extracted silica (Si) to understand its effect on the removal of naphthalene from water solution. An increase in the peak of the –OH group was observed along with the presence of other groups, viz., C–O–C, Si–O, and CH 2 . Along with the difference in characterization, a different adsorption efficiency was also found for all the adsorbents. In all the scenarios the PVA-modified APTES aerogel showed a higher removal compared to PVA-APTES and PVA-Si aerogel. The effect of different parameters, viz., pH, temperature, pollutant concentration, and aerogel dose on removal percentage were investigated. The highest removal of naphthalene was found to be 99.74% at 180 min at aerogel dose 1 g/L, pH 7, temperature 35 °C, and naphthalene concentration 5 mg/L. From the adsorption modelling it was observed that the adsorption process best fitted with Langmuir isotherm in the case of PVA-modified APTES and Freundlich isotherm for the rest of the adsorbents respectively. The kinetic analysis showed that all the adsorbents followed a pseudo- 2nd order reaction. In the pH pzc analysis of PVA-modified APTES, it was observed that the point of zero charge was detected at 7.16. It was found that the main controlling mechanism of this process was dipole-induced dipole interaction and hydrogen bonding. The effect of naphthalene on Lysinibacillus sp. before and after adsorption was observed. A significant suppression in the growth curve occurred because of the contamination of naphthalene. Graphical Abstract