3.3.4. Effect of surfactant loadingThe effect of HDTMAB and DODMAB loading concentrations(250–1000 mg L−1) on nitrate adsorption is given as Supplementarydata SD3. The nitrate adsorption% increases with increasedHDTMAB and DODMAB loading and shows a maximum corresponding to 1000 mg L−1. The increase in nitrate adsorptioncapacity for SMSs with surfactant loading may be attributed tothe formation of bilayer coverage on the modified silicates. As themonolayer formation did not cause a charge reversal on the external surface of the silicates from negative to positive, and thus theSMSs with monolayer coverage obviously could not remove thenegatively charged nitrate ions from aqueous solution by anionicexchange and electrostatic attraction. But the bilayer formationresulted in a charge reversal on the external surface of the silicates from negative to positive and the positively charged headgroups of surfactant were balanced by counter bromide ions and
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