Graphene Oxide Regulates The Hydration And Heavy Metal Solidification Performance Of Solid Waste Based Sulphoaluminate Cement

While chemical,energy,metallurgical and other industries contribute to the social economy,a large amount of heavy metal waste are discharged into the environment every year.The accumulation and discharge of these pollutants wi ll not only cause direct harm to the ecological environment,but also pose a potential threat for human health.The C-S-H gel and Ettringite in the hydration products of ordinary portland cement have great solidification capacity for heavy metal ions.Howe ver,high carbon footprint of ordinary portland cement during its production will cause irreversible damage to the ecological environment.The sulphoaluminate cement prepared prepared from common industrial solid waste（Solid-waste-based sulphoaluminate cement,WSAC）has a similar mineral composition to ordinary sulphoaluminate cement.Expect for lower energy consumption and more environmentally friendly than ordinary Portland cement,main hydration product Ettringite of WSAC has a good solidification effec t on heavy metal elements.In terms of large specific surface area,rich functional groups,good adsorption performance for heavy metals and ability to promote Ettringite crystal to grow,GO was employed to further improve the curing effect of WSAC towards heavy metals in this work.Therefore,the subject studied the effect of GO on the crystallization performance and heavy metal adsorption behavior of Ettringite,and analyzed the regulation mechanism of GO by combining a series of microscopic test methods such as XRD,SEM-EDS,FT-IR,BET and so on.The specific research content and conclusions are as follows:（1）Effect on the fluidity of WSAC.The orthogonal experiment,combing scheme range analysis method,was designed by taking GO content,water reducer content,and water-cement ratio as orthogonal factors to study the law of WSAC fluidity affected by various orthogonal factors.The experimental results show that the increase of GO content will significantly reduce the fluidity,the content of water reducer and the water-cement ratio will all have a positive effect on the fluidity of WSAC.The sensitivity sequence of fluidity to various factors is:water reducer content<GO content<<water-cement ratio.Based on the results of orthogonal experiments,the relationship between different orthog onal factors and fluidity is quantitatively analyzed through multiple regression equations and the relationship equation is:y=-89.93-398.52x₁+21.69x₂+5.3x₃.（2）Crystallization property regulation of GO on Ettringite.The paper prepared GO/WSAC and studied the effects GO bring about on hydration process of WSAC.The mechanical properties test showed that the compressive strength（1d,3d,28d）of GO-WSAC with 0.03%GO content was increased by 24.1%,18.6%and 21.5%,respectively compared with WSAC.The hydration heat,XRD and SEM-EDS test results show that the addition of GO makes the hydration process of WSAC greatly advance,the crystallization performance of ettringite is better,and the hydration products are more compact.（3）Heavy metal ions adsorption performance effect of GO on Ettringite.The adsorption effects of WSAC and GO-WSAC on heavy metal ions under different adsorption conditions were compared and studied.A series of tests including XRD,FT-IR and SEM-EDS were employed to analyze its adsorption mechanism.The adsorption results show that GO-WSAC has a faster adsorption rate and higher adsorption capacity compared with WSAC.Th e increase in pH and temperature is conducive to the adsorption of heavy metal ions.When the adsorbent dosage is 0.25g,the GO-WSAC can reach adsorption equilibrium in 10 minutes towards 400mg/L Cr³⁺solution and the adsorption rate is over 96%.The adsorption orientation order of the adsorbent to the four heavy metal ions is:Zn²⁺>Cu²⁺>Cr³⁺>Cd²⁺.