The Research On Comprehensive Utilization Of Opal-palygorskite Clay In Huangni Mountain

Huangni mountain is palygorskite main mining areas in Xuyi of Jiangsu province,There is about 100 thousand tons opal-palygorskite clay has not been effectively used and discarded or directly fill mining pit a year.The composition of opal-palygorskiteore contains about 40%attapulgite and 60%opal,and palygorskite coated on the surface ofopal.The aim of this paper is to develop the low cost dry beneficiation technology for opal-palygorskite type ore.Based on the results of dry beneficiation,opal and palygorskite was applied in preparation of sodium silicate and catalytic oxidation of formaldehyde,respectively.The high value and comprehensive utilization of opal and palygorskite ore can be realized.The main achievements of this paper are as follows:?1?The results of dry beneficiation indicate that opal-palygorskite ore opal can be effectively screened out by using 4mm diameter sieve after dry-wet cycling weathering.The main material on the sieve after 4mm screening is opal,the content is about 70%,and the main content of 4mm is palygorskite,the content is from 65%to 75%.?2?The preparation of sodium silicate based on purifiedopalfromrich palygorskiteoreby using response surface method was studied.The weighted mean of both sodium silicate modulus and leaching rate of SiO₂ was chosen as the response variables based on the single factor experiment.According to the Box-behnken center combination experiment,the reaction temperature,liquid-solid ratio and mass ratio of NaOH to SiO₂ were optimized.In addition,the statistical ANOVA analysis and confirmation tests were studied.The results showed that the sodium silicate modulus of 2.85 and leaching rate of 81.4%can be obtained at optimal parameters:reaction temperature 110?,liquid-solid ratio 6 mL/g,mass ratio of NaOH to SiO₂ 4.05:10.?3?Manganese-supported palygorskite?PG?catalysts were prepared from four manganese precursors by precipitation method and used for catalytic oxidation of formaldehyde.The purified palygorskitewas obtained from opal-palygorskite ore andusingascatalytic support.Birnessite-type manganese oxide??-MnO₂?was acquired by using potassium permanganate?PP?precursor and uniformly coated on the surface of PG.The MnO_x/PG-PP catalyst had the highest catalytic activity for HCHO.A complete conversion of HCHO to CO₂ and H₂O over MnO_x/PG-PP catalyst was achieved at 125^oC,while the same conversion over other catalyst prepared by manganese acetate,nitrate,or sulfate was obtained at 200^oC.The kinetic results of MnO_x/PG-PP catalyst show that the oxidation of HCHO followed the Mars-van Krevelen mechanism.The possible reaction pathway of HCHO oxidation was proposed based on in-situ DRIFTS.The activation energy Ea of MnO_x/PG-PP catalyst was determined to be 25.9 kJ/mol.