Application Of Nanocomposite Polyacrylamide Cryogels In Photo-Mediated Water Treatment

Water and energy are basic constituents pertaining to human life and work.As the world has been industrialized and population has grown,lacking water and water population has intensified.Meanwhile,human is facing energy crisis as the consumption of fossil energy.Currently,main methods to solve the problem of lacking water still relay on electricity and heat provided by fossil fuel,which further aggravates the energy crisis.Therefore,researchers have devoted significant efforts into solar energy(green and sustainable energy)for clean water production.In our work,photothermal evaporator and decontamination materials,which are driven by solar energy,are fabricated based on super-hydrophilic polyacrylamide(PAM)cryogel.To avoid heat loss and maximize the utilization of solar energy,we design a mushroom-like bilayer cryogel.The handle is made of porous and hydrophilic PAM cryogel with low thermal-conductivity(0.173 W-1·K-1·m-1)，and at the top is a piece of discoid PAM cryogel doped with reduced graphene oxide,which could absorb more than 90%light of the whole solar spectrum.Water is transferred to the surface of the device through porous handle and then turn into vapor due to photothermal material.Under on sun(1 kW·m-2)irradiation,the evaporation rate of water with the help of photothermal evaporator is 1.63kg·m-2·h-1,which is 3.9 times of pure water under one sun.The efficiency of solar energy for evaporation is 89.2%.Such device also performs well when applied to the evaporation of seawater and sewage.Therefore,it owns huge potential in desalination and sewage treatment as well as due to its low cost.Approach for treating organic dye in sewage includes adsorption and photo degradation,whose problem is that both adsorption agent and photo catalyst are difficult to recycle.We load polypyrrole(PPy)and titanium dioxide(TiO2)into PAM cryogel,decreasing the band gap of TiO2 due to its compositing with PPy.Thus,solar could be used for photo degradation of dye.Furthermore,PPy could adsorb dye due toπ-π interaction.In this work,we use the hybrid cryogel to treat 50 mL 10 mg/L methyl orange(MO)aqueous solution.During the adsorption process,UV-vis technique is used to examine the concentration of MO.The results show that MO could be adsorbed completely in 6 h and no MO could be detected after 3.5 h while the system is irradiated with simulated solar.This synergistic effect of adsorption and photo degradation increases the rate of removing MO significantly.Since adsorption agent and photo catalyst are integrated into PAM cryogel,it is easy to recycle the decontamination material.Such design provides an idea for sewage treatment materials.