The Study Of Interfacial Characterization Of SDS And CTAB On Bentonite Dispersions And Competitive Adsorption With Cr(Ⅵ)

This research was carried out in order to develop the research andapplication of surfactants on contaminated environment remediation.At present most researches home and abroad focused on insertion surfactantsinto bentonite interlayer, but only a few mention the change of particlescharacteristic and the interfacial characterization of different surfactants inbentonite/water dispersions under different pH values. Researches on bentonitedealing with wastewater with Cr(â…¥) mostly focused on its adsorption process,adsorption mechanism as well as removal rate of Cr(â…¥). Less researchesinvolved adsorption and coexistence effect between organic pollution likesurfactants and Cr(â…¥) existing on bentonite/water dispersions.In this paper, itwas studied that interfacial characterization of sodium dodecyl sulfate (SDS),and cetyl trimethyl ammonium bromide(CTAB) in bentonite/water dispersionsrespectively; and competitive adsorption between Cr(â…¥) and surfactant wasstudied. Then SDS-bentonite and CTAB-bentonite is prepared andcharacterized in order to provide the theory basis on the research of surfactantas modified agent for organic bentonite and remediation of soil containing suchthis system of organic pollutant like surfactants and Cr(â…¥).Conclusions of this work were drawn as follows:(1) The aggregation state, structure and surface electrical property of bentonite dispersions were changed with pH values in bentonite/waterdispersions. The experiment showed that SDS only changed the connectionwith bentonite particle, but not entered the interlayer of particles, and that theaddition of SDS could change the connection of the particles and played adifferent role in the system under the different pH values.(2) When CTAB concentration approached to CEC, CTAB⁺ mainlyexchanged with sodium ions in the interlayer in bentonite/water dispersions.CTAB⁺ entered the interlayer of bentonite, which lead to push interlayerspacing, and increased particle size. Over CEC concentration, CTAB⁺ mainlyhad the surface adsorption, so d₀₀₁-spacing nearly did not change. Moreover,zeta potential values was increased with the CTAB concentration, and at lasttended to the equilibrium.(3) In surfactant/Cr(â…¥)/bentonite system, appropriate amount of surfactantwould increase the removal rate of Cr(â…¥), because that Cr(â…¥) formedcomplexing absorption in organic level which surfactant made. The excessivesurfactant would reduce the removal rate of Cr(â…¥).(4) The result that CTAB was different from SDS in connection model wasmeasured by XRD. IR, TG, BET, Zeta potential and particle size analysis.CTAB substituted of the exchangeable cation in the interlayer area and enteredthe interlayer; which caused that CTAB-bentonite brought the positive charges,and was bigger than original bentonite in d₀₀₁-spacing, particle size, andweight loss proportion. SDS did not enter bentonite interlayer. SDS tended tothe swelling of bentonite. The negative charge of SDS bentonite particles wasless effective, because of the screening effects between the charges of narrowedges of particles and SDS molecules.