Regulation Of Halloysite Nanotube Wall Structure And Their Adsorption Performance Of Heavy Metal Ions

The clay mineral reserves of China are very rich and widely used,but it is still mainly exported as raw materials in the world industrial chain.Halloysite（Hal）is an important clay mineral with a unique hollow tubular structure and abundant surface hydroxyl groups.Its high-value applications in the fields of environment,catalysis,and biology have always been a research hotspot at home and abroad.However,the diameter,pore capacity,and loading capacity of natural halloysite nanotubes,surface adsorption performance,and other indicators have always been the difficulties restricting the further improvement of halloysite performance.There are many accompanying impurities in the tube that block the inner cavity of the halloysite.This phenomenon greatly limits the loading capacity of the halloysite and even prevents the active factor from entering the lumen.Based on this,the tube wall structure of the halloysite is removed and the particle size is classified in this thesis,and then the pore volume of the halloysite is enlarged by the freezing/thawing cycle method.At the same time,halloysite-based lead adsorption materials were also prepared.Aiming at the regulation of the halloysite tube wall structure,a new method for regulating the tube wall structure that is green,pollution-free,and does not destroy the halloysite crystal structure is proposed for the first time.This method can significantly expand the pore volume and average pore size of the halloysite nanotubes and realize the enhancement of the loading capacity in the halloysite nanotubes.This method effectively migrates the impurities in the lumen and pores of halloysite nanotubes through the principle of high-speed shear homogenization and the freeze/thaw cycle,and successfully realizes the regulation of the tube wall structure of halloysite.The total pore volume V_pore of the halloysites from Chenxi and Tongling increased by 27%and 79%respectively.The V_poreincrease rate of Hal-P-8E-CX was 37.02%,while the V_pore increase rate of Hal-P-8E-TL was 170.9%.In view of the high-value application of halloysite in the field of heavy metal ion adsorption,acid leaching and titanium hydroxyl grafting modification were carried out on halloysite in this paper,and a large number of highly dispersed and rich halloysite nanotubes（Hal-A）were grafted on it.The Ti（OH）₄ group of the hydroxyl group formed a new mineral-based adsorption material（Hal-A-Ti）.There are many hydroxyl functional groups and defect sites on the surface of the halloysite after acid leaching.Ti（OH）₄ is anchored on the inner and outer walls of Hal-A to form a dispersed tentacle structure,which increases the contact area and effectively promotes selective adsorption of Pb（Ⅱ）ions.This material has excellent renewable performance,strong selective adsorption capacity,convenient recovery,low price（25083 yuan/ton）,and can reach the adsorption equilibrium state in a very short time（2 min）.