Preparation Of Sawdust-based Porous Geopolymer And Its Adsorption Performance Of Cu(?)

With the rapid development of China's economy and the vigorous development of urban environmental protection work,some heavily polluting enterprises have begun moving to rural areas,and industrial pollution has led to severe heavy metal pollution in rural water environment and agricultural products.Sawdust can be used as adsorbents in the field of water treatment because of their porous surface structure and large amount of hydroxyl functional groups.Sawdust is derived from wood processing wastes and forestry residues(forestry pruning,dead wood),which are rich in raw materials and have low density,and can be used as an important green and renewable biological resources.Therefore,it is of great practical significance to treat heavy metal pollution with sawdust after a certain processing technology for increasing the added value of sawdust and solving the problem of water pollution in rural settlements.From the perspective of high value utilization of sawdust,high efficiency of heavy metal adsorption and the difficulty in recovery of powdered geopolymer.A novel low cost,green and environment-friendly biomass-based porous adsorption material was proposed,that is,sawdust were used as light aggregate and foaming geopolymer was used as inorganic adhesive to prepare sawdust-based porous geopolymer.Relevant parameters were designed to carry out the adsorption experiment,and the influences of key parameters such as sawdust-based porous geopolymer dosage,adsorption temperature,solution p H and wastewater heavy metal concentration on the adsorption performance were studied.The specific research contents and results are as follows:(1)Aiming at high value,scientific utilization of forestry wastes and optimization of adsorption performance for water treatment,the preparation process of sawdust-based porous geopolymer composites was explored and improved to achieve good mechanical strength,uniform bubble size and small-size microporous structure.(2)Relevant experimental studies were carried out to study the effects of sawdust-based porous geopolymer dosage,initial concentration,solution pH and adsorption temperature on the adsorption performance by designing the key adsorption parameters.The results show that when the solution pH is 5,the temperature is 25?,and the initial concentration of Cu(?)is 50mg/L,the adsorption capacity can reach21.29mg/g,and the removal rate can reach more than 80%.(3)Perform linear fitting through Langmuir adsorption isotherm model and Freundlich adsorption isotherm model to analyze adsorption isotherms.The results show that the Langmuir adsorption isotherm model can describe the adsorption process well,and the adsorption of heavy metal Cu(?)by the sawdust-based porous geopolymer is a monolayer adsorption,all adsorption sites are the same,and the adsorbed particles are completely independent.(4)Explore the change law of adsorption thermodynamic parameters,and plan to reveal the adsorption process mechanism of sawdust-based porous geopolymer.The results show that according to the standard Gibbs free energy change value?₀<0,it can be seen that the adsorption of heavy metal Cu(?)by the sawdust-based porous geopolymer is a spontaneous process.According to-42kJ/mol<?₀<-15kJ/mol,electrostatic adsorption is the main factor affecting the adsorption rate.According to the enthalpy change value?₀>0,the results show that the adsorption of heavy metal Cu(?)by sawdust-based porous geopolymer is an endothermic process.According to the entropy change value?₀>0,the entropy increases due to molecular disorder during the adsorption process,which is beneficial to the progress of the adsorption reaction.The sawdust-based porous geopolymer block composite material prepared in this study not only makes rational use of sawdust waste,but also improves its application value,which conforms to the idea of sustainable development.At the same time,the porous composite material also shows excellent adsorption performance in adsorbing heavy metal Cu(?),and has a high application potential in the field of water treatment in rural human settlements.