| Ammonium dibutyl dithiophosphate(ADD)is a widely used collector of sulfide minerals,especially for the floatation of amino-dithiophosphate.Due to its good collection ability and selectivity,ADD is widely used in mineral flotation.But the ADD has sTab chemical properties and not easily decomposed,and has a long residual time in the flotation wastewater,so its a main pollutant in the flotation wastewater.In recent years,the application and mechanism of organic bentonite in wastewater treatment and soil remediation has been a hot spot in the chemical and environmental fields.In this paper,ammonium cationic surfactants were used to modify natural bentonite to prepare organic bentonite.The X-ray diffraction(XRD),Fourier transform infrared(FTIR),thermal analysis(TGA/TG),scanning electron microscopy(SEM),specific surface analysis(N2 adsorption-desorption),and contact angle were used to characterize organic bentonite.By comprehensively using the above means,the structural characteristics of organic bentonite can be more clearly studied,and the effects of dosage,initial pH value,temperature,contact time,and a variety of organic substances on the adsorption effect when coexisting in wastewater are studied.The main findings of the paper are as follows:(1)Synthesis and characterization of organic bentonite.The organic bentonite was modified by using different quaternary ammonium salt cationic surfactants with different alkyl chain lengths,and the interlayer structure and properties of organic bentonite after adsorption of ADD were also studied.SEM,XRD,FTIR and other results show that the surfactant has been successfully loaded onto the surface and interlayer of bentonite,which is consistent with the expected target of the experiment.The specific surface area of the modified bentonite gradually decreased,and the order of the SBET size was Raw Bent>DTAB-Bent>TTAB-Bent>CTAB-Bent.Thermogravimetric data and interface contact angle results show that the organically modified bentonite increases in hydrophobicity as the alkyl chain lengths increases.Zeta potential data show that with the increase of the alkyl chain length of the modified,the charge on the bentonite surface is reversed,which is changed from negative to positive,increases the electrostatic effect.According to SEM results,the surface of organic bentonite adsorbed with ADD and the lamellar structure disappeared.The ADD was adsorbed on the surface and interlayer of bentonite,forming a tightly packed complex with the modifier,making organic Bentonite has a reduced interlaminar spacing.(2)Adsorption characteristics of ammonium butyric acid on organic bentonite.The use of 1.0 CEC surfactant modified bentonite,because of the longest alkyl chain of CTAB,can form a more hydrophobic distribution phase between the bentonite layer,so it has the highest adsorption capacity of ADD.The adsorption process is affected by the initial pH value,the pH value increases,and the removal rate of ADD decreases;when the temperature gradually increases,the removal efficiency of ADD increases first and then decreases;the adsorption process occurs within 150 minutes.Balance can be achieved.Adsorption of ADD on organic bentonite can be well fitted by pseudo-secondary adsorption kinetic model.The frequency of repeated use of organic bentonite was tested,and it was found that CTAB-modified bentonite could still reach more than 65%after repeated use four times.(3)Effect of coexisting substances in solution on the removal rate of ADD.The experimental results show that the terpilenol in the wastewater has a relatively great effect on the removal of ADD.When 10 mg/L of terpineol is added to the solution,the removal rate of ADD by the organic bentonite will decrease by about 30%.The unavoidable ion Na+ and CO32-in the wastewater have little effect on the removal of ADD,which can be neglected;the heavy metal ion Cu2+ can form a precipitate that is hardly soluble in water and organic solvents with the ADD.Removal has a promoting effect. |
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