Abstract
Adsorption of strong polyelectrolyte, poly(styrenesulfonate), PSS, of different molecular weights onto large α-Al2O3 beads was systematically investigated as functions of pH and NaCl concentrations. The ultraviolet (UV) absorption spectra of PSS at different pH and salt concentrations confirmed that the structure of PSS is independent of pH. With the change of molecular weight from 70 kg/mol (PSS 70) to 1000 kg/mol (PSS 1000), adsorption amount of PSS increases and proton coadsorption on the surface of α-Al2O3 decreases at given pH and salt concentration. It suggests that higher molecular weight of PSS was less flat conformation than lower one. The adsorption density of PSS 70 and PSS 1000 decreases with decreasing salt concentrations, indicating that both electrostatic and nonelectrostatic interactions are involved. Experimental results of both PSS 70 and PSS 1000 adsorption isotherms onto α-Al2O3 at different pH and salt concentrations can be represented well by two-step adsorption model. The effects of molecular weight and salt concentration are explained by structure of adsorbed PSS onto α-Al2O3. The influence of added SDS on the isotherms is evaluated from the sequential adsorption. The SDS uptake onto α-Al2O3 in the presence of hemimicelles can prevent the adsorption of PSS at low concentration so that adsorption of PSS reduces with preadsorbed SDS.
Highlights
Removal of organic pollutant is important for water and wastewater treatment in environmental concerns
The critical micelle concentration (CMC) of sodium dodecyl sulfate (SDS) in different electrolyte concentration was determined with a surfactant ion selective electrode that is sensitive to ionic surfactants [23, 24]
At different pH values, the spectra of PSS in the wavelength region of 200–300 nm have the same shapes with the main absorbance peaks at the wavelength of 224 nm and the secondary peak at 261 nm
Summary
Removal of organic pollutant is important for water and wastewater treatment in environmental concerns. The removal of organic contaminants by adsorption from aqueous solutions using solid surface modified with ionic surfactant or polymers (polyelectrolyte) has attracted intense studies [4,5,6,7,8,9,10]. The paper [17] indicated that the effect of added SDS and showed that SDS was preferentially adsorbed from both simultaneous and sequential adsorptions so that. Very recent study demonstrated that the presence of PSS and PDADMAC (polydiallyldimethylammonium chloride) effectively prevented different surfactants adsorption on high surface area alumina and silica by blocking charged adsorption sites [18]. The results of adsorption isotherms of PSS onto large α-Al2O3 beads with variably charged surfaces are analyzed thoroughly. The effect of the presence of SDS on the adsorption of PSS will be investigated
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