Novel hydrophilic and hydrophobic amorphous silica: Characterization and adsorption of aqueous phase organic compounds

Abstract

Very few studies have investigated the adsorption performance of hydrophobic and hydrophilic silicas with dissolved organics in water, which is a required final step during produced water treatment. The cost of functionalization also hinders the use of hydrophobic materials as sorbents. Novel hydrophilic silicas, prepared at low temperature and ambient pressure, were characterised by SEM, FTIR and BET analysis, and studied for the adsorption of aqueous phase organic compounds at concentrations below their solubility limits. Adsorption capacities were found to be up to 264 mg/g for benzene and 78.8 mg/g for toluene. Direct comparison is made with the analogous hydrophobic version of one of the silica materials, demonstrating comparable uptakes for benzene concentrations lower than 50 mg/L. This finding supports the hypothesis that, at very low aqueous phase organic concentrations, hydrophobicization has no discernible effect on access of the pollutants to the internal porosity of the material.

Organics Adsorption on Novel Amorphous Silica and Silica Xerogels: Microcolumn Rapid Breakthrough Test Coupled With Sequential Injection Analysis

“…The major physical difference is that Quartzene is produced as a powder, not as a gel from a solgel process. FE-SEM analysis of ND samples is shown in Figure 3; Z1 samples show similar surface topography to ND, while the network of Quartzene CMS is quite different (Tasca et al, 2017). Detailed surface area and pore size analysis of Quartzene have been reported previously (Tasca et al, 2017); by comparison ND samples exhibit a higher surface area (546 m 2 /g) and a narrower pore size distribution, with an average pore width of 3.3 nm.…”

“…Bottles were subsequently placed in a Gerhardt® rotary stirrer for the determination of adsorption isotherms, and associated kinetics, as well as verification of the mechanical resistance of the materials. Adsorption batch tests on the amorphous silica Quartzene have been detailed in a previous work (Tasca et al, 2017).…”

“…Within the range of available solid sorbents, hydrophobic aerogels and xerogels exhibit very attractive properties for oil spill remediation (Reynolds et al, 2001a, Reynolds et al, 2001b, Adebajo et al, 2003, Wang et al, 2012, Olalekan et al, 2014. However, very few studies have investigated the adsorption performance of hydrophobic gels at the low organic concentrations typical of water treatment applications (Simpson et al, 1993, Wang et al, 2011, Tasca et al, 2017, while the costs associated with functionalisation of these materials currently hinder their use as sorbents in the final stages of produced water treatments. It is also notable that the majority of previous work on organics adsorption from aqueous phase has been limited to batch tests, which fails to assess the feasibility of the materials developed as sorbents in apparatus commonly used in water treatment plants.…”

Fine‐tuning of phase behavior of oxazoline copolymer‐based organic–inorganic hybrids as solid‐supported sol–gel materials

“…For the material symbolized as A, the hybrid showed no transition peak. 38,40 It showed a linear dependence with transition temperature (as phase transition temperature increases, enthalpy increases) as silica act as a hydrophobic component, [41][42][43] thereby increasing the enthalpy of transition when compared with the copolymer solution (83.46 J g −1 ). It thus, tends to remain completely soluble in the water at temperature range of 20-80 C. Neither poly-oxazoline nor silica moiety was able to show phase transition.…”

“…Enthalpy changes correspond to the energy of conformational change and the hydrophobic interaction of the copolymer/silica hybrid in aqueous medium. 38,40 It showed a linear dependence with transition temperature (as phase transition temperature increases, enthalpy increases) as silica act as a hydrophobic component, [41][42][43] thereby increasing the enthalpy of transition when compared with the copolymer solution (83.46 J g −1 ). Another possible reason, which leads to the enhancement of enthalpy change of transition, could be the extension of hydrogen bonding network including acidic silanol groups.…”