Study On Modification Of Attapulgite And Its Colloidal Properties

Attapulgite clay is a natural one-dimensional nanoscale silicate mineral with the main component of attapulgite (APT). It was honored as "Thousands of earth, the king of clay" and plays important roles in many fields such as drilling mud, petrochemical, building materials, papermaking and environmental protection, etc. The nanorods of natural attapulgite prefer to exist as crystal bundles or aggregates, which limited the inherent colloid properties of APT. Thus, to develop a novel method of dissociating the crystal bundles of attapulgite and improving the colloidal propreties is significant.In this thesis, natural APT clay was soaked with natural lake water and seawater and brackish water, and the effects of soaking time on the colloid propreties were investigated. Also, the associate high-pressure homogenization and chemical modification processes were developed to disaggregate crystal bundles of APT and enhance the colloidal propreties. The main research results are as follows:1. APT clay was soaked with Qinghai lake water and seawater. The effect of soaking time on the viscosity was investigated. The results indicate that the surface charge of APT was first increased, followed by a decrease and then increase again with increasing the soaking time; whereas, the crystal structure did not change obviously. After soaking with lake water for90d, the APT suspension shows the best shear resistance capability. After soaking with lake water for180d, the rotary viscosity of APT suspension increased by100%, and the suspension stability is the best. After soaked with seawater, the optimal viscosity was obtained after soaked for60d.2. APT clay was soaked with natural brackish water, and the effects of soaking time on the viscosity, suspension stability and rheological were intensively investigated. The results indicate that the metal ions in the brackish water were exchanged with the surface ions of APT. which altered the surface charges of attapulgite and thus improved its colloidal properties. After soaking for90d, APT exhibits the best suspension stability. After soaking for180d. the rotary viscosity of APT was increased by105.7%(from1188mPa·s to2444mPa·s). 3. APT clay was modified with sodium metaaluminate (SM) in the aid of high-pressure homogenization process. The viscosity of APT was decreased after modified with SM and without homogenization. However, the viscosity of APT could increased by47.2%(from1812mPa-s to2668mPa-s) after adding high-pressure homogenization at30MPa.With increase of SM dosage, the Zeta potentialbecomes negative gradually. When the dosage of SM is0.5%, the Zeta potential value is-25.4mV.4. APT clay was modified with phytic acid (PA) in the aid of high-pressure homogenization process, and the effects of homogenization pressures on the microstructure and colloidal properties of APT were intensively investigated. The results showed that when the dosage of PA is0.1wt%, the viscosity of APT suspension was first increased and then decreased with increasing the homogenization pressure. The viscosity of APT was increased by65.3%(from1728mPa-s to2856mPa-s) after homogenization at30MPa, and the colloidal stability of the suspension was clearly increased. The modified APT may be used as a thixotropic agent and thickener, and found extensive application in many fields such as coating, printing and dyeing, paper making, daily chemical and petrochemical industry, and so on.