Use of organo-montmorillonite for the nitrate retention in water: influence of alkyl length of loaded surfactants

Abstract

The removal of NO 3 − from water was performed and compared among four organo-montmorillonites (OMt) with quaternary amine surfactants of different chain lengths [octadecyl trimethyl-(ODTMA), hexadecyl trimethyl-(HDTMA), tetradecyl trimethyl-(TDTMA) and dodecyl trimethyl-ammonium (DDTMA)] and loadings [100%, 200%, 400% of the Mt cation exchange capacity (CEC)]. The maximum adsorption of NO 3 − was attained by the long chain length surfactants (64 and 100 mg NO 3 − ions per gram of OMt, for HDTMA and ODTMA, respectively) with initial loading of 400% with respect to the CEC of Mt. The short chain length surfactants (DDTMA and TDTMA) did not show adsorption of NO 3 − except for TDTMA 400 sample. The NO 3 − adsorption produced a slight expansion of the interlayer thickness of the OMt samples loaded with long-chain surfactants that was assigned to the entrance of NO 3 − by a synergic effect with these surfactants. The decrease of the negative zeta potential, found for OMt samples relative to that of Mt sample, was attributed to the surfactant chain length rather than to the actual surfactant loaded amounts, which allowed attaining positive zeta potential values for the OMt loaded with long-chain surfactants. The NO 3 − adsorption on OMt samples caused a slight decrease in the positive zeta potential values, reflecting the external surface coating by NO 3 −. For long-chain molecules, this behaviour also indicated the formation of greater interactions such as ion pairs between the positive polar group of the surfactant and NO 3 − ions.

Insight into (Electro)magnetic Interactions within Facet-Engineered BaFe12O19/TiO2 Magnetic Photocatalysts

“…This was controlled by a combination of FTIR and zeta (ζ) potential measurements, as shown in Figure . The NO 3 – presence after the synthesis is observed as a sharp peak at ∼1384 cm –1 , and the residual PEG molecules are noticed due to weak bands at 840–860 and ∼1100 cm –1 , characteristic for C–O and C–C vibrations, respectively, observed previously for PEG . Both of these signals are mostly hindered after the calcination, which is accompanied by the shift of the observed isoelectric point (IEP) to the higher pH value, similar to the one reported previously for the BaFe 12 O 19 prepared by calcination at 1000 °C .…”

Monitoring and Management of Anions in Polluted Aqua Systems: Case Studies on Nitrate, Chromate, Pertechnetate and Diclofenac

“…Jaworski et al [124] used montmorillonite modified with various ammonium surfactants to (1) introduce positive charges into the inorganic host and ( 2) to open up the montmorillonite layer structure to improve the accessibility of internal sites. The importance of the interlayer opening is illustrated by the fact that in most cases no removal of nitrate was observed with short chain surfactants while with longer chain surfactants the exchange/removal capacity increased.…”

Arsenate removal from aqueous solution by montmorillonite and organo-montmorillonite magnetic materials

“…The presence of functional groups such as hydroxyl, carboxyl and epoxy promote the adsorption of arsenic on the surface of clays. Previous experiments (Barraqué et al, 2018;Bianchi et al, 2013;Jaworski et al, 2019) have revealed that quaternary ammoniums compounds (QAC) loading at values higher than the CEC, modify the Mt surface electrical charge from negative to positive, allowing them to be used to remove inorganic oxyanions.…”