Organo-clays (hexadecil trimethyl ammoniun and gelatin-Montmorillonite) as Humic Acid adsorbents

M. FERNANDEZ; JUN ZHU; R. M. TORRES SÁNCHEZ

Rio de Janeiro

Congreso; XV International Clay Conference; 2013

Association Internationale pour l`Étude des Argiles; Sociedade Brasileira de Geoquímica

The use of organo-clays, from quaternary ammonium molecules (as hexadecyl-trimethyl-ammonium, HDTMA) and montmorillonite (MMT) or hectorites clays, have shown significant improvements in polymers properties such as mechanical, thermal and gas barrier [Paul et al., 2005; Lepoittevin et al. 2002; Gorrasi et al., 2003). Also, organo-clays had also been used in remediation where non-polar organic molecules as pesticides generated the water pollution (Celis et al., 2007). The organo-clays, from gelatin montmorillonite, could be also associated to treat pesticides groundwater contamination, being these organo-clays more environmentally friendly than those obtained from quaternary ammonium molecules. Remotion of organic matter (or humic acid) by clays from water was largely studied. In addition, the hydrophobic character of a surface with long alkyl chains result from a complex interplay between the structure of carbon chains and the interactions of polar areas humic acid. From this behavior organo-clays, (from gelatin-MMT and gelatin-HDTMA-MMT) are proposed for the adsorption of organic matter, using as a model molecule the humic acid (HA). To attain this, 2 and 10% gelatin was added to MMT suspensions to obtain G2-MMT and G10-MMT samples and HDTMA bromide concentration corresponding to 1 CEC of the MMT originated the HDTMA-MMT sample. A fraction of the HDTMA-MMT was also exchanged with 2% gelatin (G2-HDTMA-MMT). All products were characterized by XRD, apparent diameter and Zeta potential curves. The d (001) spacing of G2-MMT and G2-HDTMA-MMT samples respect to that of MMT, showed an increase of 1.58 and 1.87 nm, respectively, indicating the insertion of the respective organic molecules. The subsequent adsorption of HA, showed no significant interlayer change. The presence of gelatin in G2-, G10-MMT+HA and G2-HDTMA-MMT+HA samples showed a sorption decrease of around 20% respect to that achieved in MMT+AH sample, while for G10-HDTMA-MMT+HA, adsorption was close to that for MMT+HA sample. Dapp values, indicative of tactoid?s agglomeration, for G2-MMT+HA samples maintain the same relative increase and approximate values to than found for G2-MMT. While in G2 and G10-MMT-HDTMA+HA samples, the gelatin increase generated a strong agglomeration, reducing the Dapp values of G10-MMT-HDTMA+HA sample twice over that found for G2-HDTMA-MMT+HA and more than 58 times compared to G10-HDTMA-MMT, assigned to electrostatic attractions of the organic compounds on the surface of the initial MMT. The favorable agglomeration of these new adsorbents could to advantage the coagulation process and streamline the process of separation. The zeta potential values of G2 and G10-MMT+HA samples were similar to the respective samples without HA, while the HA sorption. In the samples G2-MMT-HDTMA+HA and G10- HDTMA-MMT+HA produced an increase of negative charge and a sign change, respect to the corresponding samples without HA.