Effects Of Dissolved Organic Matter On Carbamazepine Adsorption On Minerals

Dissolved organic matter(DOM)has important effects on natural ecosystems and biological health because they can alter significantly the transport and availability of contaminants in soils and water.To explore the effects mechanisms and conditions of DOM on carbamazepine(CBZ)adsorption behavior by minerals,a series of DOM and CBZ batch techniques were conducted respectively,and the mechanisms were investigated with dialysis and ultrafiltration.In this study,the DOM and contaminant were prepared by humic acid(HA)and CBZ,respectively;mineral adsorbent selected kaolin and quartz mixture.The interactions in system of DOM-CBZ-minerals were discussed comprehensively by three aspects: sorption behaviors of DOM/ CBZ,combinations between DOM and CBZ,and the effects of DOM on CBZ adsorption were also studied by some factors such as concentration,molecular weight and minerals.The main conclusions of this paper are as follows:(1)As the results of DOM characterization,the DOM of this study is mainly macromolecules.H-HA(>10k Da)contains more hydrophobic structures,with strongest aromaticity and weakest polarity.L-HA(<3k Da)comprise more hydrophilic structures,with strongest polarity.M-HA(3k-10 k Da)has greater hydrophobicity and hydrophilia.(2)In the sorption experiments of DOM,larger fractions can be preferentially adsorbed by minerals.Besides,different fractions show different adsorption capacities because of various properties.The sorption amount of H-HA is bigger than M-HA apparently,L-HA not adsorbed,which suggests that major interaction of DOM with minerals is large and hydrophobic fractions combining with minerals surface by hydrophobic and Van der Waals interactions,and polar reactions rarely occur.(3)The main chemical reaction mode between CBZ and DOM is that CBZ's aromatic ring and amidogen react with HA by ?-? interactions and polar interactions respectively according to FTIR results.In addition,dialysis results suggest that CBZ exists mainly in the fraction of the molecular weight <1k Da,so the bond between CBZ and HA are weak.Hydrophobic attraction is the main reaction when CBZ concentration is lower;while polar bond will increase as CBZ concentration elevates.(4)The influence of DOM on CBZ adsorption is related to the adsorption property of DOM.For mixture solid,the lower concentration and lower molecular weight DOM with weak adsorption capacity can inhibit CBZ adsorption due to solubilization or competition.However,with concentration or molecular weight rising,the sorption capacity of DOM also enhances,which is advantageous to CBZ adsorption because of co-sorption or cumulative sorption.For quartz,the stronger adsorption of DOM can promote CBZ adsorption.