Study On The Load Characteristics Of Modifier In Montmorillonite Interlayer And Its Effect On The Structure Of Modified Montmorillonite

Bentonite is generally used as an adsorbent in wastewater treatment due to its unique layered structure and large specific surface area.The composite modified bentonite with alkyl ammonium and complexing agent is a new type of adsorption material with important application prospect in wastewater treatment.In this study,alkyl ammonium and complexing agent cysteamine hydrochloride(CSH)were used as modifiers to modify the sodium montmorillonite.The effects of alkylammonium structure and preparation conditions on the loading amount,occurrence mode of modifier in montmorillonite interlayer and the structure of the composite modified montmorillonite were systematically studied.Subsequently the adsorption mechanism of modifiers onto montmorillonite was discussed.The main conclusions are as follows:1.The amount of cetyltrimethylammonium chloride(CTAC)used in the amount ratio of modifiers CSH/CTAC has a decisive effect on the loading,occurrence mode of the modifiers in the montmorillonite interlayer and interlayer spaces of the modified montmorillonite.The loading amount of CTAC in montmorillonite interlayer and the interlayer spaces of the composite modified montmorillonite increases with increasing the CTAC amount,while the loading amount of CSH decreases.Moreover,with the increase of the CTAC amount,the mixed-layer structure appears on the modified montmorillonite,and the CTAC cations in montmorillonite interlayer change from liquid-like state to solid-like.The increase of CSH dosage has no obvious effect on the loading amount of the modifier in the montmorillonite interlayer and the interlayer spaces of the composite modified montmorillonite.2.The carbon chain length and benzyl structure of alkyl ammonium have significant influence on the loading amount,occurrence mode of modifier in montmorillonite interlayer and the structure of the composite modified montmorillonite.With the increase of the carbon chain length of alkyl ammonium,the interlayer spaces and weight loss rate of the composite modified montmorillonite increase,and the intensity of C-H symmetric stretching vibration absorption band near 2850 cm-1 is higher.When the alkyl ammonium with benzyl group was used to modify the montmorillonite,the loading amounts of the modifier in the sodium montmorillonite interlayer decreases,but the interlayer spaces and weight loss rate of the composite modified montmorillonite are correspondingly increased.3.For the composite modified montmorillonite prepared under the different adding order of modifiers,the loading amount of CTAC and CSH in the montmorillonite interlayer and the interlayer spaces of the composite modified montmorillonite does not change significantly,but the CTAC loading amount is much larger than that of CSH,which indicates that CTAC is more easily adsorbed by montmorillonite than CSH,and the CSH entered into the montmorillonite interlayer may be replaced by CTAC.4.The reaction time has a significant effect on the loading process of CTAC and CSH on the sodium montmorillonite.With the extension of the modification time,the loading amount of the modifier in montmorillonite interlayer increased rapidly and then increased slowly,and reached equilibrium at 10 min.The intercalation process of CTAC and CSH on the sodium montmorillonite is well described by the pseudo-second-order kinetics model,and CTAC can enter into the montmorillonite interlayer faster than CSH.5.The reaction temperature has little effect on the loading amount of CTAC and CSH on the sodium montmorillonite.With the increase of the modification temperature,the loading amount of CTAC and CSH in montmorillonite interlayer does not change much.The Redlich-Peterson isotherm model can better simulate the intercalation process of CTAC and CSH on the sodium montmorillonite,indicating that the adsorption of CTAC and CSH on the sodium montmorillonite may be mainly on the non-uniform pores or surfaces of montmorillonite.