Study On Preparation,Structure Characteristics And Adsorption Performance Of Multicomponent Modified Bentonite To Heavy Metal Ions And Phenol

Bentonite,known as "omnipotent soilr",is attracting more attention from people becauseof its water absorption,swelling ratio,ion exchange properties,and strong adsorption of environmental pollutants.Because of the low prices and resources-rich of the bentonite inChina,its adsorption performance can be obviously improved via organic,inorganic or organic-inorganic composite modification.It has important theoretical significance and application value to further study the modification mechanism,structure characteristics and adsorption mechanism of pollutants of bentonite,and to research and develop the economic and efficient bentonite adsorption material.In this study,the sodium bentonite is chosen as raw material,the long carbon chain cationic surfactant cetyl trimethyl ammonium bromide?CTAB?,polycarboxylic organic complexing agent L [ L = diethylene triamine pentaacetic acid?DTPA?,ethylene diamine tetraacetic acid?EDTA?,citric acid?CTA?] and hydroxyl aluminium aggregation(AI¹³)as modifying agent to prepare modified bentonites.And two series of organic composite modified bentonite?CTAB-L-Bent?and multicomponent modified bentonite(Al¹³-CTAB-L-Bent)sorptive materials was synthesized.The effects of preparation method,the total dosage of modifier,the proportion of surface active agent and complexing agent,and the structure of the organic complexing agent on structures of modified bentonite were investigated.The structure characteristics and forming mechanism of modified bentonite we discussed.And then the sorption mechanism,influencing factors and change laws of modified bentonites as adsorbents to simultaneously adsorb the organic pollutants phenol and heavy metals M²⁺(M²⁺ = Cd²⁺,Cu²⁺,Ni²⁺,Pb2+)from the mixed solutions were studied.The mainworic and original conclusions of the thesis are summarized as follows:?1?The preparation,structure characteristics and formation mechanism of organic composite modified bentonite CTAB-L-Bent.CTAB and L?DTPA,EDTA,CTA?were used as the composite modifier agents to modify Na-Bent by means of simultaneous method and fractional step method.The formation mechanism of CTAB-L-Bent is best conceived of as:when via the fractional step method preparation of CTAB-L-Bent,CTAB was intercalated into the layers of bentonite by cation exchanging,and then L was introduced into the layersthrough the coulomb force?or hydrophobic interaction?between the organic matter by way of exchange and the surface adsorption.But when via simultaneous method preparation of CTAB-L-Bent,There is a synergistic intercalating effect between CTAB and L.That is to say CTAB and L form firstly an entirety by electrostatic forces and hydrophobic bonding,and then which intercalated into the layers of bentonite by cation exchanging with the interlayerexchangeable cation ions.?2?The adsorption properties and adsorption characteristics of organic compositemodified bentonite CTAB-L-Bent.The influence factors of the adsorption properties of three different CTAB-L-Bent were studied via single factor experiment.The adsorption capacity of CTAB-L-Bent to phenol and heavy metal ions M²⁺(M²⁺ = Cd²⁺,Cu²⁺,Ni²⁺,Pb2+)is different,the relation of the adsorption capability intensity is CTAB-DTPA-Bent > CTAB-EDTA-Bent >CTAB-CTA-Bent,which is directly proportional to the interlayer space of corresponding CTAB-L-Bent.The adsorption mechanism of phenol on CTAB-L-Bent is mainly controlled by a partition process of phenol in the long carbon chain organic hydrophobic media.And at the other conditions are constant,their adsorption capability strengthens with the elongating of the complexing agent chains1 length.However,the adsorption mechanism of heavy metal ions M²⁺(M²⁺ = Cd²⁺,Cu²⁺,Ni²⁺,Pb2+)on CTAB-L-Ben is mainly dominated by the heavy metal ions complexing reaction of the complexing agents L,and their adsorption capacity strengthens with the increase of interlayer complexation sites.?3?The preparation,structure characteristics and formation mechanism of multicomponent modified bentonite Al¹³-CTAB-L-Bent.Na-Bent has been modified using AI¹³-CTAB-L as the multicomponent modifier agents by means of simultaneous method and fractional step method.XRD,IRj SEM analysis results show that the interlayer space of AI¹³-CTAB-L-Bent further increases,as well as the surface properties are also changed significantly.Both kinds of preparation methods can achieve the purpose of modified bentonite,but in comparison,synchronization method is relatively simple,can simplify the process of preparation,shorten the preparation time,save costs,and is conducive to industrialization.Under the condition of the dosage of AI¹³ invariable,the interlayer space of AI¹³-CTAB-L-Bent increases with the increasing of the dosage of composite modifier CTAB-L.On the condition of the total amount of multicomponent modifier agents are invariant the interlayer space of Al¹³-CT AB-L-Bent is directly proportional to At the other conditions are constant,the longer the carbon chain,the bigger the molecule of Ltand the larger the interlayer space of AI¹³-CTAB-L_Bent,that of AI¹³-CTAB-DTPA-Bent >AI¹³-CTAB-EDTA-Bent > AI¹³-CTAB-CTA-Bent.The formation mechanism of Al¹³-CTAB-L-Bent is best conceived of as: when via the fractional step method preparation of AI¹³-CTAB-L-Bent, was intercalated into the layers of bentonite by cation exchanging to form AI¹³-Bent,and then CTAB and L as an entirety was introduced into the layers through the electrostatic interactions and the surface adsorption,whereas when via simultaneous method preparation of AI¹³-CTAB-L-Bent,there is a synergistic intercalating effect between AI¹³,CTAB and L.that is to say Ain,CTAB and L form firstly an entirety by electrostatic forces and hydrophobic bonding,and then which intercalated into the layers of bentonite by cation exchanging with the interlayer exchangeable cation ions.Due to the synergistic intercalating effect,Al¹³-CTAB-L-Bent has larger interlayer space and better adsorption performance.?4?The adsorption properties and adsorption mechanism of multicomponent modified bentonite Al¹³-CTAB-L-Bent.The influence factors of the adsoq)tion properties of three.different Al¹³-CTAB-L-Bent were studied via single factor experiment.AI¹³-CTAB-L-Bent as adsorbents can simultaneously remove the organic pollutants phenol and heavy metals M²⁺(M²⁺ = Cd²⁺,Cu²⁺,Ni²⁺,Pb2+)from the mixed solutions.The adsorption capacity of phenol onAl¹³-CTAB-L-Bent is better than that of CTAB-Bent and CTAB-L-Bent.And the adsorption capacity of heavy metals M²⁺ on Al¹³-CTAB-L-Bent is stronger than that of Na-Bent,Ain-Bent and CTAB-L-Bent.The adsorption mechanism of phenol on Al¹³-CTAB-L-Bent is mainly controlled by a partition process of phenol in the long carbon chain organic hydrophobic media as well as surface adsorption.And at the other conditions are constant,their adsorption capability strengthens with the elongating of the complexing agent chains' length,with of the sequence of adsorption capacity: Bent < Ain-Bent < Al¹³-CTAB-Bent <CTAB-CTA-Bent < CTAB-EDTA-Bent < CTAB-DTPA-Bent.However,the adsorption mechanism of heavy metals M²⁺on Al¹³-CTAB-L-Bent is mainly dominated by the metal ionscomplexing reaction of the complexing agents L and hydroxyl-aluminum as well as surface adsorption.And their adsorption capacity strengthens with the increase of interlayer complexation sites,with of the sequence of adsorption capacity: Bent < Al¹³-CTAB-Bent <AI¹³-Bent < AI¹³-CTAB-CTA-Bent < Al¹³-CTAB-EDTA-Bent < Al¹³-CTAB-DTPA-Bent.?5?The multicomponent modified bentonite used to treatment the mineral processing wastewater was preliminarily discussed.The results indicate that CTAB-L-Bent and AI¹³-CTAB-L-Bent adsorption materials show a good adsorption capability to the heavy metal ions and COD in the mixed wastewater,which is an economic and efficient water treatment adsorption materials and has some practical application prospect.