Preparation And Adsorption Performance Of Modified Bentonite

The Chinese bentonite reserves is the highest in the world but, in practice, direct application ofnatural bentonite is seldom. Because the natural bentonite is affected by its own restrictions, the adsorptioncapacity can not meet the requirements of pollution control.Modified bentonite is a multi-functionalmaterial and has been playing an important role in pollution-controlling. Therefore further study on themodification of bentonite will bring out a bright prospect of economical and social benefits. The betterinput dosage of modified bentonite was3.0g as a whole.A novel absorbent was prepared using Na-bentonite modified with cetyltrimethyl ammoniumbromide and quaternized chitosan. According to the different adsorption object, the best preparationconditions of organic bentonite were determined; the ability of modified bentonite to remove organicpollutants from aqueous solutions and the simultaneous absorption of the organic pollutants and heavymetals onto the modified bentonite from the mixed solutions had been studied.In the single adsorption experiment, the main parameters, including modified bentonite dosage,initial pH value of solution, oscillation time of adsorption, adsorption temperature and additionalelectrolytes, were discussed. The results of XRD and IR proved that the original soil had been modified byHACC and CTMAB; the better input dosage of modified bentonite was3.0g as a whole; the contactingtemperature and pH value of the solution had no influence on the adsorption of aniline; the organicmodified bentonite, in alkaline environment, was in favor of phenol adsorption and the maximumadsorption was observed at pH12. The adsorption of phenol on modified bentonite favored at20℃; theadsorption equilibriums of aniline and phenol were both attained in40minutes and the adsorptionprocesses both fitted well the pseudo-second-order kinetic; additional electrolytes could promote theadsorption of aniline onto modified bentonite, but the presence of additional electrolytes decreased itheadsorption of phenol. The regeneration performance of the organic bentonite was studied, the resultsshowed the modified bentonite had a good regeneration performance, in the treatmeant of aniline,0.1 mol/L HCl solution could be used for the regeneration of organic bentonitethe.; in the treatmeant of phenol,1.0mol/L NaOH solution could be used for the regeneration of modified bentonite.In the composite adsorption expriment, the major factors of the modified bentonite for aniline,phenol and Cd2+were investigated. Summarize the relevant rules: the better input dosage of modifiedbentonite was4.0g as a whole. the presence of Cd2+had basically no influence on the adsorption of anilineand phenol, but the presence of aniline and phenol promoted the adsorption of Cd²⁺; modified bentonite hada strong removal in wide range of pH(3-9); modified bentonite with organic layer could rapidly adsorpaniline and phenol and the adsorption equilibriums of Cd²⁺was attained in40minutes; the adsorptionprocesses both fitted well the pseudo-second-order kinetic. The main adsorption mechanism was differentbetween the organic pollutants and heavy metal onto modified bentonite. The main adsorption mechanismof aniline and phenol was partitioning effect, and the main adsorption mechanism of Cd²⁺was chelatingeffect.Thermodynamics curves of single and compound pollutants onto modified bentonite were drawnat20℃. Langmuir and Freundlich models were used to fit dates. In the single experiment, analysis of theresults showed that the pattern of adsorption for aniline followed Freundlich models; the pattern ofadsorption for phenol followed both Langmuir and Freundlich models. In the composite adsorptionexpriment, analysis of the results showed that the pattern of adsorption for aniline and phenol followedFreundlich models, however, Langmuir and Freundlich models could not be used to describe adsorptionbehavior of Cd²⁺. Therefore, the corresponding reasons need to be further explored in the future.