| With the rapid development of my country’s social economy,environmental problems often arise.In the production process of some industrial sectors,a large amount of industrial sewage containing heavy metals will be produced,which will lead to heavy metal pollution after entering the water body.The intractability and irreversibility of heavy metals make the accumulation and transfer of heavy metals through the food chain（network）,and finally enter the human body,plants and animals,which seriously threatens human health.At present,there are many technologies for treating heavy metal pollution in water.Among them,adsorption method is the most widely used due to the advantages of various adsorbent materials,simple preparation method and low cost.Geopolymer（GP for short）is a kind of inorganic polymer,which is formed by activation and polymerization of aluminosilicate material,and has good adsorption performance for heavy metals.In this paper,natural volcanic tuff was used as the synthetic raw material,sodium hydroxide and water were added as activators,and lignocellulose was added as a modified material to form a new type of geopolymer composite material（L-GP for short）.The effects of different dosages of alkaline activators and different doping ratios of volcanic tuff and lignocellulose on the heavy metal adsorption properties of geopolymers were explored,and the optimal preparation conditions were formulated.L-GP and geopolymers（GP for short）synthesized from only volcanic tuff were prepared under the same preparation conditions,and the effects of dosage,p H,time,temperature,and initial ion concentration on doped lignocellulose were investigated.The effect of GP on the adsorption of Pb（II）and Cu（II）before and after was compared,and the effect of doping lignocellulose on the adsorption performance was demonstrated by comparison,and the related data were combined with adsorption kinetics and adsorption isotherm to judge whether the two materials were the same type of adsorption.The functional groups,crystal composition,pore structure and other material properties of the two GPs were compared by FTIR,XRD,BET,SEM and other characterization methods,and the related mechanism was briefly described.The following research results were obtained:（1）The results show that the optimal preparation conditions of the composite geopolymer L-GP:60%Na2O（Na OH）as an alkaline activator,the doping ratio of LNC and VT is 1:1.Under the premise of the characteristic tetrahedral structure of the geopolymer,the surface of L-GP presents more abundant active groups,which effectively improves the adsorption performance.（2）L-GP and GP have good adsorption capacity for Pb（Ⅱ）and Cu（Ⅱ）.The effects of L-GP and GP dosage,p H of solution,initial metal concentration,adsorption temperature and adsorption time on the adsorption of Pb（Ⅱ）and Cu（Ⅱ）were investigated by single-factor experiment method.The maximum saturated adsorption capacities of L-GP and GP for Pb（Ⅱ）were 460.83 mg·g-1and 223.21 mg·g-1,when the maximum saturated adsorption capacity for Cu（Ⅱ）can reach 99.90 mg·L-1and 46.49 mg·L-1.When Pb（II）and Cu（II）coexist,there is a competitive adsorption phenomenon between them,and the order of adsorption of heavy metal ions by the two geopolymers is Pb（II）>Cu（II）.The adsorption processes of Pb（II）and Cu（II）by GP and L-GP fit the second-order kinetic law and the Langmuir isotherm model.The adsorption of Pb（II）by the two materials belongs to the monolayer adsorption and is mainly composed of It is controlled by chemisorption and is an entropy-increasing endothermic reaction that proceeds spontaneously.（3）It is proved by FTIR characterization analysis that the adsorption material prepared by introducing LNC during the polymerization reaction not only retains the structural characteristics of GP,but also enables LNC to successfully attach to GP,making it more powerful than ordinary GP.Rich in active groups,the adsorption capacity is greatly improved.In addition,XRD analysis shows that LNC has a large amount of calcium source,and the addition of calcium source interacts with silica and aluminum during the polymerization reaction,forming a gel with adsorption activity,which is also the better adsorption capacity of L-GP than GP.one of the factors.At the same time,through BET analysis,it was found that the specific surface area and pore size of L-GP prepared by doped lignocellulose were larger than those of GP,which are key properties favorable for heavy metal adsorption.（4）No matter which ions are adsorbed,the adsorption capacity of L-GP prepared by doping LNC is more than twice that of GP.It can be seen that the addition of LNC can significantly improve the adsorption performance of GP.This thesis has important guiding significance for how to improve the adsorption performance of GP and use volcanic tuff and lignocellulose to prepare high-performance GP and its potential applications. |
