Preparation、Characterization Of Organic Bentonite And Its Adsorption For Phenolic Compounds In Wastewaters

The emission of coking wastewater is more and more at present,it will be a great harm to human and even the whole wildlife chain if be directly discharged because that there are large varieties of toxic pollutants in it and they are difficult to be treated by biochemical means,moreover,the most abundant contents in coking wastewater are phenolic compounds and ammonia nitrogen,thus study on adsorption of phenolic compounds in coking wastewater has extremely significance. Bentonite because of its abundant resources and special physico-chemical properties and layer structure as a sorbent material has a great application potential in wastewater treatment,natural bentonite has limited application in wastewater treatment due to its strong hydrophilicity, a large number of studies have shown that modified bentonite can improve its physical and chemical properties, and increase its adsorption capacity,so the modified bentonite will have a good application prospect in the coking wastewater treatment.In this article,firstly,two kinds of typical cationic surfactant long carbon chain surfactant cetyl trimethyl ammonium bromide (CTMAB) and short carbon chain surfactants with a benzene ring benzyl trimethyl ammonium bromide (BTMAB) were used to modify the bentonite by traditional mechanical mixing to prepare organic bentonite CTMAB-Bent and BTMAB-Bent,Then CTMAB-Bent and BTMAB-Bent were used for adsorption of phenolic compounds (phenol、p-nitrophenol、o-methylphenol and o-chlorophenol)in simulated coking wastewater after primary treatment,after adsorption conditions and rules of single phenolic compounds were detailed discussed,total adsorption rate of four kinds of phenolic compounds and the interaction between adsorbate also were studied.CTMAB-Bent and BTMAB-Bent were charactered by XRD and BET analysis,and were applied to adsorption of phenolic compounds in simulated coking wastewater after primary treatment in the same conditions. The results showed that CTMAB and BTMAB can both be intercalated to layers of bentonite,compared to Ca-Bent,layer spacing of CTMAB-Bent and BTMAB-Bent increased,specific surface area,pore volume decreased.the adsorption capacity of CTMAB-Bent to four kinds of phenolic compounds is better than BTMAB-Bent because that the layer spacing of CTMAB-Bent is more bigger and the Closely、larger skeleton of benzene ring of BTMAB-Bent to to prevent phenolic compounds to enter.CTMAB-Bent were used for adsorption of phenolic compounds (phenol of initial concentration of300mg/L、p-nitrophenol of initial concentration of20mg/L、o-methylphenol of initial concentration of500mg/L and o-chlorophenol of initial concentration of10mg/L)in simulated coking wastewater after primary treatment, the modified quantity of CTMAB, additive amount of modified bentonite and adsorption time on the influence of adsorption rate were detailed discussed.The results showed that when modified quantity of CTMAB was1.0CEC, adsorption time was1h, dosing quantity of CTMAB-Bent were1.5g,0.1g,1.0g and0.1g,adsorption rate reached best were84.14%,98.22%,92.85%and84.7%respectively.The adsorption process of four phenolic compounds by1.0C-Bent were both better conforms to Langmuir equation and Freundlich equation and the maximum theory adsorption amount of o-chlorophenol (294.12mg/g)> o-methylphenol (243.90mg/g)> p-nitrophenol (92.59mg/g)> phenol (66.67mg/g) were positively correlated with octanol-water partition coefficient (Kow).Adsorption thermodynamics and kinetics studies showed that adsorption of four phenolic compounds by1.0C-Bent are spontaneous exothermic reaction, adsorption process is a simple physical adsorption and conducive to the adsorption of low temperature,it is conformed to secondary dynamic model.CTMAB-Bent were used on two of four phenolic compounds mixture adsorption treatment, the experimental results showed that when the equilibrium concentration of four phenolic compounds is low and adsorption mechanism is distribution function,adsorbate between each other has good synergistic effect; whereas,when the equilibrium concentration of four phenolic compounds is high and adsorption mechanism is surface adsorption function, adsorbate between each other has competitive effect.The total adsorption rate and adsorption amount of four phenolic compounds by1.OC-Bent was92%and19.27mg/g respectively.