Study On The Preparation Of Oily Sludge-Based Geopolymer And Solidification/Stabilization Of Cd²⁺,Cu²⁺ And Cr³⁺

Oil is an indispensable energy resource in people’s daily life and industrial production,but the oil industry generates a large amount of oily sludge in the process of production,transportation and storage.The composition of oily sludge is complex,containing a large number of toxic heavy metals and organic pollutants,and improper disposal or inadequate treatment can pose a serious threat to the environment and human health.Therefore,the resource utilization of oily sludge has been the focus of researchers.Geopolymer is a green inorganic polymer material with good mechanical properties,corrosion resistance and low permeability.Oily sludge with silica-alumina content is a potential source of silica-alumina for geopolymer preparation.In addition,the geopolymer solidification/stabilization technology can encapsulate the toxic heavy metals in the oily sludge,and the resulting oily sludge-based geopolymer can be reused as construction materials,which can significantly increase the added value of the oily sludge and realize the harmless treatment and resource utilization of the oily sludge at the same time.Based on this work,the optimal preparation of oily sludge-based geopolymer under experimental conditions was obtained,and the immobilization of Cd²⁺,Cu²⁺and Cr³⁺was tested using the geopolymer solidification/stabilization technique,and the solidification effect of cement and oily sludge-based geopolymer on Cd²⁺,Cu²⁺and Cr³⁺was compared.The effect of cement and oily sludge-based geopolymer on the solidification of Cd²⁺,Cu²⁺and Cr³⁺was compared,and the acid and alkali resistance of the heavy metal solidified body of oily sludge-based geopolymer was also tested,and the mechanism of Cd²⁺,Cu²⁺and Cr³⁺immobilization by oily sludge-based geopolymer was investigated.The main conclusions are as follows:（1）The optimal solution for the oily sludge-based geopolymer was obtained by single-factor test and orthogonal test with the raw materials of oily sludge and coal gangue:50 wt.%of activated coal gangue,6 mol/L of sodium silicate,0.45 of liquid-solid ratio and 45℃of curing temperature,and the compressive strength of the prepared oily sludge-based geopolymer reached the highest value under the test conditions,with a compressive strength of 42.5 MPa at 28 d.The strength was in accordance with the requirement of 42.5 grade ordinary silicate cement in GB175-2007"General purpose silicate cement".The structure type of the oily sludge-based geopolymer hydration gel is mainly PSS with Si O₂ and Al₂O₃ ratio of 2 and PSDS with Si O₂ and Al₂O₃ ratio of 3.The hydration products are mainly hydrated sodium/calcium silicate.（2）By comparing the immobilization effect of three different heavy metal ions Cd²⁺,Cu²⁺and Cr³⁺in the oily sludge-based geopolymer,it was obtained that the immobilization efficiency of Cd²⁺,Cu²⁺and Cr³⁺are all greater than 99%,and the oily sludge-based geopolymer has good immobilization ability for all three heavy metal ions,and all three heavy metal ions are successfully immobilized in the geopolymer.The order of the immobilization ability of the oily sludge-based geopolymer for the three heavy metal ions was Cd²⁺﹥Cr³⁺﹥Cu²⁺.Under the same conditions,the leaching concentration of cement heavy metal solidified body was significantly higher than that of oily sludge-based geopolymer,and the immobilization ability of oily sludge-based geopolymer for Cd²⁺,Cu²⁺and Cr³⁺was much higher than that of cement.In addition,the leaching concentration of heavy metal solidified body of oily sludge-based geopolymer is still lower than the maximum allowable risk value in GB5085.3-2007"Hazardous waste leaching identification standard-leaching toxicity identification"after acid or alkali leaching,showing good resistance to acid and alkali.（3）Combining XRD,FTIR,SEM-EDS and XPS test methods for comparative observation and analysis,it was demonstrated that heavy metal ions participate in geopolymerization through substitution of Ca/Na or direct linkage as Si-O-T or Al-O-T（T:Cd,Cu or Cr）.Hence,the mechanism of heavy metal immobilization is by ion exchange balancing charge or chemical bonding in the geopolymer structure.Figure[50]Table[24]Reference[116]...