Formation Mechanism Of Organic-Mineral Complexes Affected By Various Values Of C/M In Conditions Of Different Temperature And Pressure

To discuss the formation and adsorption mechanism of organo-mineral complexes(Com)with different organic matter contents under different pressure and temperature,commercial humic acid as the organic matter and kaolin as the clay mineral were used to form the Com0(Com was formed under normal pressure and temperature(NPT))and Com1(Com was formed under high pressure and temperature(HPT))with different value of C/M(organic matter contents).Carbamazepine(CBZ)as molecular organic pollution and tetracycline(TC)as ionic organic pollution were used in the adsorption-desorption batch experiment,with the characteristic analysis by means of the Fourier infrared spectrum(FTIR),X-ray diffraction(XRD),specific surface area analysis(SSA)and scanning electron microscope(SEM),to find features of the sorption and structure of Com0 and Com1 changed with the increasing values of C/M.The results are concluded as:(1)In NPT,when the organic matter contents are small(values of C/M less than1%),humic acid and kaolin were interacted together to form the Com0 with mechanisms such as intercalation reaction,pore-filling of kaolin and the reactions between functional group of humic acid and kaolin;When the value of the Com0 is1%,humic acids became saturated in the formation mechanism of pore-filling and reactions between functional groups,and that results in the emergence of the reaction between free humic acids and humic acids on the Com0's outer space;When the organic matter contents are larger(values of C/M are between 1%-10%),besides the formation mechanisms above,reactions of humic acids on the Com0's outer space were becoming the main formation mechanism,including the hydrogen-bond interaction and the electrostatic attraction.(2)In HPT,when the values of C/M were less than 1%,except part of the humic acids reacted with Kaolin(the same as Com0),the surface functional group “–OH” of part Kaolin were consumed in HPT,and part of the humic acid were aggregated together on the surface of the Com1.When the organic matters contents became larger(values of C/M were between 1%-10%),which the main mechanisms were reactions between humic acids,because of the HPT,polymerization was the mainreactions between humic acids,differed from formation mechanism in NPT.(3)In general trend,the increase of the organic matter contents facilitated the sorption of different organic pollutants of Com.However,some differences changes were found in the special value of C/M,and that showed the different sorption mechanism in different organic pollutants.Because of the molecularity and hydrophobicity of the CBZ,sorption reactions with Com were mainly hydrophobicity and ? bonds reactions,and that resulted in the high sorption capacity of the Com when the value of the C/M was 1%.When it came to TC,with the amphoterism(with hydrophily and hydrophobicity existed at the same time)of the ionic feature,there were different sorption mechanisms in it.Kaolin came as the main adsorbent when the organic matter contents was small.And when the values of the C/M became larger,humic acid became the main adsorbent.Both of the desorption hysteresis of CBZ and TC were the highest when the value of C/M is 1% of Com.(4)In NPT,Sorption capacity of CBZ of Com0 was larger when the value of C/M was 1%,which was smallest of TC in Com0.In HPT,because of the polymerization of humic acid,aromatization and hydrophobicity of the Com were increased,and that resulted in the promotion of adsorbability of Com1 in CBZ.When it came to TC,adsorbability of Com1 became weaker when organic matter contents were small,resulting from the loss of functional groups(-OH),which were consumed in HPT.Comparing with the Com0,there wasn't a higher sorption capacity of TC shown in the Com1,which was differed from CBZ.