Improvement Of Xinyang Low-grade Bentonite And Its Functional Research

Bentonite is an important inorganic non-metallic material,which is amongst the earliest non-metallic minerals used by human society.Because of its excellent properties such as water absorption expansion,suspension,thixotropy,and adsorption,it is widely used in the petrochemical industry,metallurgy,environmental protection,and other industries.There are abundant bentonite resources over our contrary,mainly including calcium bentonite and low-grade bentonite.These bentonites are always with unsatisfied physical and chemical properties,such as water absorption,dispersion,and suspension,limiting their direct application.Therefore,it is necessary to improve the performances of natural low-grade bentonites and further expand their application fields.In this dissertation,the modified bentonites with excellent properties were successfully prepared via various modifications on Xinyang low-grade bentonite,and their applications in drilling,suspension,and metallurgy were explored.The details are attached as follows:（1）Sodium bentonite was prepared by a method of semi-dry aging using Xinyang low-grade bentonite.The effects of the usage of modifier Na₂CO₃and reaction time on the properties of modified sodium-bentonite were studied systematically;how did the dosage of light-weight Mg O,cellulose ether,sodium carboxymethyl cellulose,and polyacrylamide（APAM）affect the viscosity,loss,and dynamic/plastic ratio of drilling bentonite mud were also discussed.Moreover,we optimized the synergist by orthogonal tests.The results indicated that the optimizing sodium conversion conditions of low-grade bentonite include the dosage of Na₂CO₃was 2.5 wt.%and the reaction time was 1.5 h.In this way,the interlayer spacing of bentonite was reduced from 1.4918 nm to1.2690 nm,and its filtration was reduced from 89 m L to 31 m L.The above four synergists were adsorbed on the surface of bentonite particles,and none of them were inserted into the bentonite layers.Furtherly,the components（1 wt.%Mg O-1 wt.%APAM）of the synergist that can meet the technical requirements of drilling bentonite were decided by the orthogonal tests.The modified sodium-bentonite using the optimized synergist possesses theΦ600 of 34 m Pa·s and the filtration of 12 m L.（2）Sodium bentonite and lithium bentonite were prepared by wet modification,and their optimum conditions were determined.Besides,how these modified bentonites affect the properties of water-based coatings and quick-drying alcohol-based coatings were investigated.The results suggest that the interlayer spacings of bentonites treated with sodium modification and lithium modification,respectively,decrease significantly from 1.4918 nm to 1.2987 and 1.3541 nm.There are lots of flakes on the surfaces of modified bentonite particles,which are the remarkable characteristics of sodium and lithium bentonite.When the modified bentonites were used as the suspension agents for water-based coatings and quick-drying alcohol-based coatings,the performances of the coatings such as suspension,viscosity,and brushing were improved.（3）Based on experimental studies,the water absorption of sodium-bentonite was further improved by combining extrusion and aging when adopting Na₂CO₃as the modifier.The optimal conditions were determined,and sodium bentonite with water absorption of 397%in 2 h was prepared.The quality of pellets could be muchly improved when the as-prepared sodium bentonite cooperates with CMC-Na,and the compound binder including 4 wt.%sodium-bentonite and 0.2 wt.%CMC-Na could meet the production requirements.We further make it clear that the usage of sodium bentonite meeting the pellet production requirements can be as low as 3 wt.%by optimizing the ratio of the binders.