The Construction And Performance Evaluation Of Bentonite Composite Adsorption Material

Bentonite(Bent),due to its rich abundant,low-cost,large surface area and high cation exchange capacity,has been widely applied in wastewater treatment areas.However,its hydrophilicity,permanent negative charge and difficult separation limited it further utilization as the adsorbent toward anionic dye adsorption.Modification of bentonite was essential for the better application of wastewater treatment,as its negative charged surface and morphology.In this paper,the bentonite was modified and treated with intercalation by cationic surfactant and introduction of functional group to improve its adsorption capacities toward various dyes.Moreover,due to the difficult separation of powdered adsorbents,the composites beads and coating film adsorbents were constructed to improve its separation efficiency.The modified adsorbents,with excellent adsorption and easy separation,were beneficial to the treatment of practical dye manufacturing wastewater.The main researches as follows:1.A novel adsorbent,carboxymethyl cellulose(CMC)grafted by poly(2-(dimethylamino)ethyl methacrylate)modified bentonite(Bent/CMC-g-P(DMAEMA))composite,was synthesized.Its structure was characterized by SEM,TEM,XRD,TG,FT-IR,Zeta potential and nitrogen sorption measurements.Various compositions of Bent/CMC-g-P(DMAEMA)by varying the amount of CMC with 20%,50%and 80%(wt%)in total amount of CMC+Bent,coded as 20CMC-Bent,50CMC-Bent and 80CMC-Bent,respectively,were prepared.The 20CMC-Bent exhibited excellent adsorption capacity toward MO and higher qmax(110.7 mg g-1)was obtained.The adsorption property of 20CMC-Bent in the cationic and anionic binary dyes system,methylene blue(MB)/MO was also investigated.The results showed that both MO and MB could be removed effectively and sodium dodecyl sulfate exhibited selective suppressing effect toward MO in the binary system.Three isotherm models in linear and non-linear regressions were employed and assessed by various error functions and the possible adsorption mechanism was also proposed.2.The gelatin/bentonite composite beads(Gel-Bent)were facilely prepared by compacting gelatin and bentonite and characterized using SEM,XRD,FT-IR,TGA and Zeta potential.The tunable adsorption property of Gel-Bent toward the anionic dye CR and cationic dye MB was investigated by changing the mass ratio of bentonite to gelatin.The CR and MB maximum adsorption capacities(qmax)were obtained with Gel-6.25%Bent(123.72 mg g-1)and Gel-50%Bent(107.39 mg g-1),respectively.The effect of contact time,temperature and pH on the adsorption of CR and MB onto Gel-12.5%Bent was investigated.Its selective adsorption property in the MB/CR binary system was evaluated under the co-presence of anionic surfactant SDS and inorganic salt NaCl at various pHs.Three isotherm models in linear and non-linear regressions,and two kinetic models were employed and assessed by various error functions.In addition,the swelling behavior of the composite beads was studied and the possible adsorption mechanism was also proposed.3.Filter paper(FP)acted as flexible and renewable substrate,cationic surfactant intercalated CTAB-bentonite nanoparticles in thin poly acrylic acid(PAA)coating layer(PAA/CTAB-Bent-FP)composite adsorbent was synthesized,and characterized by SEM,FTIR,XRD,TG and nitrogen sorption measurements.The adsorption and separation performance of PAA/CTAB-Bent-FP toward dyes was investigated.The results of adsorption studies revealed that the anionic dye ORII and cationic MB both could be adsorbed onto PAA/CTAB-Bent-FP efficiently and rapidly by simple filtration,80%ORII and 86%MB removal efficiency within 150 s at moderate dye initial concentration were achieved by 30%PAA/CTAB-Bent-FP(30wt%of CTAB in amount of Bent).More importantly,this removal process of dyes by PAA/CTAB-Bent-FP realized rapid adsorption of dyes(anionic and cationic dyes)and simply separated simultaneously by conventional filtration operatioa The recycle was easily and feasible in high MB concentration system-In the fifth cycle,96.2%MB removal was obtained,suggesting that 30%PAA/CTAB-Bent-FP can be used as an effective adsorbent for MB removal.As a practical feature,it should be emphasized that the PAA/CTAB-Bent-FP material worked at a wide pH range and could be used either as a solid adsorbent or a membrane for continuous wastewater treatment.