Study Of Modifided Halloysite Nanotubes For The Removral Of Dyes

Industrial dye wastewater may block the transmission of light,limit photosynthesis,inhibit biological growth,generate toxicity to aquatic organisms,and thus affecting the diversity of aquatic organisms.For this reason,regeneration and recycling of dye wastewater are of great significance for human health and ecological environment protection.However,due to their stable chemical structures,most dyes are hardly decomposed completely by traditional methods including photodegradation,oxidative degradation and biodegradation,and some of them are too expensive to operate.Adsorption is a simple and effective method to remove contaminants,in which the performance of the adsorbent is the key to removal efficiency.In this work,halloytsite nanotubes(HNTs)were used as raw material to prepare an adsorbent due to their properties of rich resource,low price and availability.To increase the dispersibility and selective adsorption capacity,these HNTs were further modified by different approaches.Simultaneously,desorption and regeneration conditions were investigated,thus a new type of adsorbent with high efficiency,low cost and good recycling performance was developed.The main research contents and conclusions are as follows.(1)The HNTs were purified by acid activation.Field emission scanning electron microscopy(FESEM),Fourier transform infrared(FT-IR)and X ray diffraction(XRD)were used to characterize the surface morphology,functional groups and structures.Results showed that HNTs exhibited hollow tubular structure with two open ends,and especially the large specific surface area and ratio of length to diameter provide favorable conditions for the next modification.The adsorptions of cationic dyes,anionic dyes and nonionic dyes on the activated HNTs were respectively investigated.It was found that the activated material showed better adsorption performance for cationic dyes,while the adsorptions of anionic and nonionic dyes were poor.(2)In order to improve the dispersibility and consequent adsorption capacity of HNT,amino modified HNTs(NH2-HNT)were synthesized with aminopropyltriethoxysilane(APTES)and characterizd by FESEM,FT-IR,XRD,and N2 adsorption-desorption.Through study on selective adsorption,the cationic dye of malachite green(MG)was selected as the target.The effects of pH value,system temperature,adsorption time,initial concentration of the dye and the adsorbent dosage on the removal efficiency of MG were studied.Furthermore,regeneration and recycling utilization of the materials were investigated after adsorption.The results showed that the as-prepared materials displayed excellent adsorption efficiency for MG at the pH range of 4~10,and the adsorption capacity increased with the increase of temperature,initial concentration of the dye and adsorbent dosage.Under the optimal conditions,the materials could remove the MG with the contention as low as 0.01 mg/g and the maximum adsorption capacity reached 48.4 mg/g,which increased by 101.7%.Moreover,the material had excellent regeneration property with 90 % removal efficiency after four cycles.The equilibrium data fitted well with Langmuir isotherm and the kinetic properties were well described by the pesudo-second-order equation.Satisfactory results were also obtained for the removal of MG in real water samples with adsorption efficiency of97.1~99.0%.(3)The HNTs were modified with cationic surfactant of hexadecyl trimethyl ammonium bromide(HDTMA),and the obtained organic-inorganic composite materials(HDTMA-HNTs)were characterized by FT-IR,thermogravimetry(TG),and N2 adsorption-desorption analysis.Then the modified materials were used as adsorbent for different types of dyes,and the results showed that HDTMA-HNTs exhibited better adsorptive capacity for nonionic dyes.Taking disperse rubine as the example,which is hardly to remove,the effects of pH value,system temperature,adsorption time and adsorbent dosage on the adsorption performance were studied.It was found that its adsorption capacity on HDTMA-HNTs reached 130 mg/g.Kinetic studies showed that the adsorption fitted well with pesudo-second-order model and the equilibrium data fitted well with Langmuir isotherm.Good results were observed when the material was applied to remove disperse rubine from practical wastewater.