Preparation And Adsorption Properties Of Mesoporous Calcium Silicate And Its Composites With Graphene Oxide And Nano-zero Valence Iron

Heavy metal and organic dye wastewater has become the two major problems of water pollution.Compared with the traditional treatment methods,adsorption technology provides a simple operation,low cost,and suitable for dealing with various types of wastewater.It has great potential in practical applications.The most important is the choice of an efficient adsorbent.Mesoporous calcium silicate was used as the object of study in this paper,Preparation of mesoporous calcium silicate by template and hydrolysis method,and then preparation of composite materials by supported grapheme oxide.The adsorption properties and adsorption mechanism of heavy metal ions were investigated;Preparation of the nanoscale zero valent iron/mesoporous silicate composites to study the effect of the removal of methyl orange.?1?A series of calcium silicate were prepared using calcium nitrate and sodium silicate as raw materials by means of template synthesis method and the effects of the removal method of template on its structure and morphology.Which were synthesized were characterized by theinfraredspectrum,x-raydiffraction,scanningelectronmicroscopeand Brunauer-emmett-teller.The specific surface area of mesoporous calcium silicate prepared by removing the templating agent by washing with water was 244.32 m²/g,and the channel is rich and clear.But the washing process is more cumbersome,firing method to remove the template will affect its pore structure,they are large pores and the specific surface area of only7.31 m²/g.The mesoporous calcium silicate was prepared by hydrolysis method using ethyl orthosilicate and calcium nitrate tetra hydrate as raw materials.The method has the advantages of simple operation and large specific surface area of the mesoporous calcium silicate,which is 206.17 m²/g,and the surface pores are rich.Both calcium silicate crystals are hydrated calcium silicate.?2?The isothermal adsorption,kinetics and thermodynamics of Cu²⁺,Zn²⁺,Cd²⁺,Mn²⁺and Ni²⁺on the two kinds of mesoporous calcium silicate were investigated.The adsorption mechanisms,selective adsorption and regeneration properties of the agent in this paper.The adsorption of Cu²⁺,Zn²⁺and Cd²⁺on the mesoporous calcium silicate by hydrolysis method is in accordance with Langmuir model,which is the ideal monolayer adsorption.The adsorption capacity decreased in the order of Cu²⁺>Cd²⁺>Zn²⁺.The adsorption of Mn²⁺and Ni²⁺on the mesoporous calcium silicate by template was in accordance with the Freundlich model,and the adsorption capacity was Ni²⁺>Mn²⁺.The kinetic data indicate that the adsorption process of heavy metal ions by two kinds of mesoporous calcium silicate can be better described by the pseudo-second-order model,and the higher temperature is favorable for the reaction.The thermodynamic results show that the adsorption process is endothermic reaction??H>0?and spontaneous??G<0?,reflecting the entropy increase principle,The adsorption mechanism of the mesoporous calcium silicate by the hydrolysis method shows that the adsorption effect of the three kinds of heavy metals is the best when the p H is 6,the acidity will affect the pore structure of the adsorbent,and the alkaline conditions will precipitate the metal ions.The exchange of metal ions with calcium ions in the adsorption process,and the exchange of calcium ions and heavy metal ions adsorption capacity is proportional to the size.Mesoporous silicate of Cu²⁺,Cd²⁺,Zn²⁺selectivity certain adsorption strength of selectivity:Cu²⁺>Cd²⁺>Zn²⁺,which consistent with the size of adsorption capacity.The equilibrium adsorption capacities of Cu²⁺,Cd²⁺,Zn²⁺were 6.81 mmol.g^-1,3.5 mmol.g^-1 and 3.32mmol.g^-1 at 293K.Indicating that the size of adsorption capacity can reflect the strength of adsorption selectivity.Both materials have excellent regenerative properties.?3?The adsorption properties of Cu²⁺were investigated by the method of hydrolysis of mesoporous calcium silicate as carrier and compound gravel with graphene oxide.The graded graphene was intercalated in mesoporous calcium silicate channels by infrared,X-ray diffraction,scanning electron microscopy and BET.The pore size was mainly distributed at10-30 nm,which was mesoporous.Compared with the original calcium silicate the specific surface area has decreased.Composites and Cu²⁺at 293K,the addition amount of 0.01 g,0.02g and 0.03 g of the mesoporous silicate GO equilibrium adsorption capacity of the composite material were 7.03 mmol.g^-1,7.11 mmol.g^-1,and 6.91 mmol.g^-1.With the increase of GO addition,the adsorption capacity of Cu²⁺increased first and then decreased.The optimum dosage is 0.02g.the equilibrium adsorption capacity at this temperature is higher than the original calcium silicate 6.81 mmol.g^-1.And with the increase in the amount of GO,that the adsorption of heavy metals play a positive role.The adsorption process is mainly chemical adsorption,ideal single-layer adsorption,and more in line with Langmuir model.The adsorption kinetic model shows that the quasi-second-order adsorption kinetics model is more suitable for describing the adsorption of mesoporous adsorbents to heavy metal ions,and the elevated temperature contributes to the increase of adsorption rate.More than the original calcium silicate can be faster to achieve a balance of 60 min.The adsorption thermodynamics of Cu²⁺in composites shows that the adsorption process is an endothermic reaction,which is the process of entropy increase.The regeneration performance of the composites was strong,and after 6 times of the elution cycle,the removal rate decreased by only 6.8%.?4?The nanometer zero-valent iron was prepared by reduction with Na BH4 and then loaded onto mesoporous calcium silicate to prepare composite materials.The samples were characterized by X-ray diffraction and scanning electron microscopy and transmission electron microscopy.Successfully loaded onto mesoporous calcium silicate,and can be uniformly dispersed on the channel of the carrier.From the two factors of economic and effect analysis,mesoporous calcium silicate loaded nano-zero-valent iron is better than nano-zero-valent iron and mesoporous calcium silicate,zero-valent iron and calcium silicate the best mass ratio of 1:10,When the reaction temperature is 293K and the p H is neutral,the removal efficiency of methyl orange is better.This ratio of composite materials in the treatment of copper and methyl orange and zinc and methyl orange composite pollution,not only the effect is better than the original calcium silicate on a single heavy metal ion,but also keep a good removal effect of methyl orange.This paper focuses on the adsorption of heavy metals and organic dyes on adsorbent materials,and provides excellent adsorbents for the practical application of materials.It is a kind of new adsorbents with great development value.