Chromium removal using organo- and bio-Montmorillonites

FERNANDEZ MORANTES, C.; CURUTCHET, G.; TORRES, R.

Rabdeuil

Conferencia; 7th Mid-European Clay Conference; 2014

Chromium is one of the most abundant inorganic groundwater contaminants at hazardous waste sites.Compared to Cr(III), the Cr (VI) forms chromate (CrO42−) or hydrogen chromate (HCrO4−) that is more toxicand more soluble under different pHs and because of the negative charges, its adsorption on aquifer mineralsis limited.The conventional treatment of chromate-rich effluent is based on the reduction of Cr(VI) to Cr(III) andprecipitate Cr(III) as chromium hydroxide, or chromium iron hydroxide at high pHs, resulting in a veryexpensive treatment. Clays are extensively used as low cost Cr adsorbents (Dimos et al., 2012). Recentlyan improvement in the Cr adsorption efficacy was indicated for surfactant treated montmorillonite or organomontmorillonites(OMMT) (Kumar, et al, 2012).In this work Cr(VI) adsorption was evaluated in: a raw MMT, a OMMT (exchanged with octadecyltrimetilammoniumBromide) and a bio-MMT (obtained by growing Acremonium sp), denoted O-MMT and Acre-MMT, respectively.The maximum adsorption for all samples was found at pH 3. The Chromium adsorption on O-MMT sampleshowed maximum adsorption at all pH respects to the other samples. At pH 3 the Cr adsorption valueobtained for OMMT agree with data obtained by Kumar et al (2012).The XRD analysis of MMT, O-MMT and bio-MMT samples indicated reflection peaks (001) values at 1.26,2.12 and 1.24 nm, respectively. These data indicate that ODTMA enters as pseudotrilayers or paraffin-likemonomolecular arrangements, while the fungi specie does not enter in the interlayer. The samples after Cradsorption at pH 3 showed different behaviors of the reflection peaks (001): for MMT an enlargement wasfound while for O-MMT and bio-MMT samples not changes were found. In agreement with Kumar et al (2012)the apparition of new XRD peaks at 23.47 and 51.23 °(2θ) confirmed the Cr adsorption.The negative Zeta potential values of MMT sample (-30 mV) was reduced after Cr adsorption, indicating aneutralization of the edge positive charges. For O-MMT sample the Cr adsorption diminished the positivecharge of O-MMT sample from +20 to +15. While for bio-MMT sample no changes were found in the Zetapotential, remaining the Zeta potential values around -28 mV.