Preparation Of Chitosan Based Composite With Copper And Its Characteristic Of Solar Evaporation

With the development of industry and the rapid growth of population,the shortage of fresh water resources is becoming more and more serious.Therefore,the effective treatment of heavy metal wastewater to protect the scarce fresh water resources,and the use of solar energy for efficient desalination to increase the amount of fresh water,are the necessary measures to alleviate the shortage of fresh water.In this paper,the cheap and environmental friendly special biomass chitosan was used as carbon-based materials,and the solid-phase grinding in-situ synthesis method was used to make it fully combined with copper nitrate(Cu(NO₃)₂·3H₂O)to prepare carbon-based composites containing copper,and to test whether it has good photothermal conversion performance.Then,the adsorption product of chitosan adsorbing copper ion wastewater was carbonized to make full use of the organic solid waste generated from the wastewater treatment of printed circuit board(PCB)industry and combine it with solar desalination to make full use of resources and further alleviate the shortage of fresh water.The specific research contents are as follows:Firstly,Chitosan and copper nitrate were used as raw materials,and then C-Cu O composites were prepared by a simple one-step calcination method.C-Cu O composite filter paper films were prepared by suction filtration spin coating method.The optimal calcination temperature(250?)and mass ratio(1:1)of C-Cu O composite prepared by one-step calcination method were selected by comparing the film temperature rise rate and the highest equilibrium temperature in the experiment of light film temperature rise.The effect of the amount of C-Cu O composite on the evaporation performance of C-Cu O composite filter paper film was investigated.The results show that the load of C-Cu O composite can effectively improve the evaporation performance of the film,and under the light intensity of 1 k W m^-2,the evaporation performance of the film is 0.015 g C-Cu O composite filter paper film showed good stability in the cycle experiment.The evaporation rate and evaporation efficiency were about 1.34 kgm^-2 h^-1 and 88.39%,respectively.Secondly,Chitosan porous adsorbent(CPA)was prepared by freeze-drying method and used to treat simulated low concentration copper ion wastewater(200 mg L^-1).It was found that the effect of copper removal was good,and the saturated adsorption capacity was 136.63 mg g^-1.Compared with the SEM images,it can be observed that the copper containing carbon matrix composites(CCM)prepared by two-step calcination at 550?have better porous structure.The results of X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)show that the copper containing carbon matrix composites are mainly composed of amorphous carbon and copper oxide,with a small amount of cuprous oxide.CCM filter paper composite film was also prepared by suction filtration spin coating method.In the evaporation experiment under the light intensity of 1 k W m^-2,0.020 g of CCM dosage can achieve the optimal evaporation effect.At this time,the evaporation rate is 1.36 kg m^-2 h^-1,and the evaporation efficiency can reach 89.89%.The stability of CCM filter paper composite film was tested by cyclic experiments with different light intensity,and it was found that the film had good durability.Finally,Based on the comparison of the evaporation performance of solar thermal conversion materials in the first two chapters,it is found that CCM has good photothermal conversion performance and can realize the effective utilization of resources by calcining the waste adsorbing copper ions at 550?in two steps and using it for solar evaporation.An evaporator(PAM-PVA-CCM)with high efficiency of photothermal conversion was prepared by using a porous cellulose polyacrylamide hydrogel with a three-dimensional structure.By means of FT-IR,it was found that the addition of photo thermal conversion material CCM did not affect the synthesis process of hydrogels.Tensile tests showed that the hydrogel had good flexibility and maximum tensile strength of 0.44 MPa.Moreover,the hydrogel has a high absorptivity and absorbs 97.4%in the wavelength range of 250-2500 nm.The designed device A4 was used to carry out the seawater evaporation experiment under the light intensity of 1 k W m^-2.The evaporation rate and evaporation efficiency reached 1.80 kg m^-2 h^-1 and 91.6%respectively.The evaporation experiments of different light intensity and salt concentration showed that PAM-PVA-CCM hydrogel can well meet the normal light intensity in real life.Under the condition that the brine concentration is not more than 10 wt.%,the evaporation device A4 can maintain the dynamic balance of water in the evaporation experiment,and has good illumination applicability and anti-salt accumulation ability.At the same time,cyclic experiments showed that PAM-PVA-CCM hydrogel had good stability.In terms of seawater desalination,by comparing the concentrations of main salt ions in seawater before and after desalination,it was found that the concentrations of Na⁺,Mg²⁺,K⁺and Ca²⁺decreased significantly to below 5 mg L^-1,far meeting the standard limit of Na⁺drinking water(200 mg L^-1)set by the world Health Organization.