Preparing Cu-C Composite Material By Lactic Acid Bacteria Adsorption And The Solar Evaporation Characteristics Of Its Self-floating Aerogel

The importance of fresh water resources is self-evident.Due to differences in regional distribution and population density,many regions on a global scale are affected by water shortage to varying degrees.Using widely available seawater for desalination to expand fresh water production is an effective solution.On the other hand,with the development of industry,the pollution of heavy metal ions further threatens the safety of human freshwater.The biological adsorption method has the characteristics of high efficiency,low cost and wide adaptability in the prevention and control of heavy metal copper ion pollution.At the same time,it is noted that the products of this method are rich in copper and carbon elements,while copper-based semiconductor materials and carbon based materials can be used as efficient photothermal conversion materials,which can convert light energy into heat energy through the photothermal conversion effect and be utilized.Solar energy is hailed as the“energy of the 21st century”because of its clean and sustainable characteristics.Desalination and evaporation of salt water by solar energy is one of the applications of high efficiency photothermal conversion materials.This technology uses the energy generated by photothermal conversion for evaporation of salt water,and then collects fresh water by condensation,effectively increasing the amount of fresh water.And by breaking the limitations of high cost,high energy consumption and high pollution of traditional methods,solar desalination becomes an important direction of the development of seawater desalination field.Therefore,it is of great significance and value to use biological adsorption of copper ion products to prepare high efficiency photothermal conversion materials.And using them in solar water evaporation and seawater desalination can achieve the decrease of the cost of existing photothermal conversion materials,the reduction of copper pollution and the alleviation of water crisis.In this thesis,starting from the above point of view,firstly,lactic acid bacteria adsorbed copper ions to prepare copper-containing bacteria mud,and then carbonized to obtain Cu-C composite photothermal conversion material.By analyzing the elements and chemical components before and after lactic acid bacteria adsorption and carbonization,the successful introduction of copper element was determined,and the feasibility of preparing efficient photothermal conversion materials through biological control of copper ion pollution products by lactic acid bacteria was confirmed.Secondly,the Cu-C composite photothermal conversion material was introduced into agar,and self-floating aerogels was prepared by integrated pouring with insulation layer.By changing the structure of the insulation material,two kinds of aerogels with peripheral water-lifting structure and central water-lifting structure were prepared.Both aerogels were then tested experimentally.It was found that when the addition of photothermal material was 0.3 g and the height ratio of evaporation layer to insulation layer was 1:1,the evaporation performance was the best.Under the light intensity of 1k W m^-2,the evaporation rate and evaporation efficiency reached 1.60 kg m^-2 h^-1 and82.6%,respectively.For the central water-lifting aerogel,the optimal evaporation performance was also obtained at a 0.3 g load and the ratio of height of evaporation and isolation layer was 1:1,but the maximum evaporation rate and evaporation efficiency were higher than that of the peripheral one,which was 1.65 kg m^-2 h^-1 and 87.5%.The experiment on the influence of light intensity showed that both evaporation rate and evaporation efficiency were needed to achieve high efficiency solar evaporation.In addition,the results of cycling stability test and seawater desalination experiment showed that the two aerogels with different water-lifting structures had good stability and seawater desalination ability,and the concentration of ions(Na⁺,Mg²⁺,K⁺and Ca²⁺)of the desalinated water successfully reached the drinking water standard of the World Health Organization（WHO）.As a whole,the comprehensive performance of the central water-lifting aerogel was better than that of the peripheral one.Finally,according to the thermodynamic properties and migration properties of the fluid,the finite element analysis software COMSOL Multiphysics was used to construct the water-heat-salt multi-field coupling mathematical models of two kinds of self-floating aerogel,and the steady-state temperature field,steam field and salt concentration field of the solar water evaporation experiment were numerically simulated.The results showed that the data of simulation and experiment are consistent with each other,which provided technical support for theoretical analysis of experimental results.It was worth noting that the salt distribution field showed two different potential applications of the two aerogels,which can be used to develop salt-resistant and salt-collecting evaporators,respectively.There are 40 figures,7 tables and 102 references in this thesis.