Preparation Of Halloysite Nanocomposites And Its Application In Seawater Desalination

In recent years,the shortage of freshwater resources has become increasingly serious,and it is urgent to develop practical and feasible seawater desalination technologies to obtain drinkable freshwater.The solar interface evaporation technology has attracted wide attention from the industrial and academic communities due to its advantages of green,low cost,and high efficiency.Polymer composite materials with excellent light absorption ability are ideal materials for solar interface evaporators.There are still challenges in improving their hydrophilicity and water transport capacity during the interface evaporation,improving the efficiency and rate of interface evaporation,ensuring material interface stability and long-term durability,and enhancing the purification ability of multi-component seawater.This paper uses halloysite(HNTs)with hollow hydrophilic tube cavities and easily modified outer tube walls with hydroxyl groups as the basic construction unit of the evaporator.Polymer materials with photothermal conversion ability are modified onto the outer surface of HNTs,and efficient two-dimensional and three-dimensional polymer composite solar interface evaporators with superhydrophilicity and salt resistance are prepared through interface regulation,expanding the versatility of seawater desalination evaporators.The paper consists of the following three parts:1.First,Polyaniline(PANI)was modified to the outer surface of HNTs by electrostatic and hydrogen bonding,giving HNTs excellent photothermal properties.By using the ultrasonic induced interface sintering,PANI/HNTs were firmly fixed on the surface of polyurethane(PU)nanofiber membrane.While retaining the porous structure of PU membrane,the mechanical properties of PU membrane were improved by strong interface effect.In addition,the hydrophilicity of PANI and HNTs was improved,The rough and porous microstructure of PANI/HNTs enhances the hydrophilicity of the composite material,and the 2D interface evaporator constructed with large pore PVA sponge with fast water transport performance can achieve spontaneous exchange of salt water under concentration gradient and gravity drive,ultimately resulting in a super hydrophilic,stretchable,and salt resistant interface evaporator that can be used for long-term sea water desalination,with an evaporation rate of 1.61 kg·m-2·h-1.2.By the hydrogen bonding between dopamine(DA)and HNTs,a layer of PDA was successfully modified on the surface of HNTs.Subsequently,the PDA/HNTs were carbonized to obtain carbon encapsulated HNTs(CHTs)with excellent photothermal conversion ability.Based on the second chapter,the superhydrophilic PVA sponge was directly modified with CHTs to prepare an integrated 3D seawater desalination evaporator.Through effective thermal management,the CHTs/PVA evaporator has broken through the evaporation efficiency limit of traditional two-dimensional evaporators,with an evaporation rate of up to 2.4 kg·m-2·h-1.In addition,the 3D seawater desalination evaporator has shown excellent salt resistance in long-term seawater desalination experiments,and through photothermal action,it can absorb high viscosity crude oil floating on the water surface before seawater desalination.3.Through a simple one-step method,HNTs and PDA were directly introduced on the surface of melamine sponge.In addition to having higher evaporation performance(3.5 kg·m2·h-1)compared to CHTs/PVA composite sponge evaporators,interface evaporation can also drive efficient adsorption of heavy metal ions,which is superior to traditional oscillating adsorption.In long-term seawater desalination experiments,HNTs and PDA have shown excellent salt resistance,and ultimately achieve efficient interface evaporation A seawater desalination process that integrates rapid adsorption of heavy metal ions inside.