Preparation And Adsorption Properties Of High Strength Chitin/Chitosan Porous Aerogels

Azo dyes and heavy metal ions in the discharge of industrial and agricultural wastewater have a significant impact on people’s drinking water safety.At present,the main methods of wastewater treatment are chemical precipitation,membrane separation,ion exchange,photocatalysis,biodegradation and adsorption technology.Among them,adsorption has become one of the most effective decontamination methods because of its low cost,easy operation,high efficiency and low risk of secondary pollution.The key to determine the quality of adsorption technology lies in the materials of adsorbents,so the selection of adsorbents is particularly important.In recent years,aerogel has been widely studied as a new adsorbent because of its superior physical properties.Therefore,a new type of Chitin/chitosan aerogel（HPS-aerogel）was prepared by using biomass compounds chitin and chitosan as raw materials,which was used as a new adsorbent material to adsorb azo dyes and heavy metal ions.Congo red（CR）and Cu²⁺ions were selected as azo dyes and heavy metal ions respectively.The specific research contents of this paper are as follows:1.A high-strength aerogel with a 3D hierarchically macro-meso-microporous structure（HPS-aerogel）was designed based on biological macromolecules of chitin and chitosan.The macropores can be created within HPS-aerogel after Ca CO₃ removal,and meso-micropores resulting from water sublimation during freeze-drying.The macro-meso-microporous structure endowed HPS-aerogel with high porosity（98.16%）,good mechanical properties,and excellent compression strength（1472 k Pa at strain of80%）.At the same time,this structure also greatly improves the water absorption and water retention.2.The HPS-aerogel exposed many adsorption sites and was used as an adsorbent to simultaneously remove copper ions(Cu²⁺)and Congo red（CR）from water.The adsorption capability for Cu²⁺and CR was 59.21 mg/g and 2074 mg/g at 303 K,respectively,and the adsorption processes matched Pseudo-second-order and Langmuir models with spontaneous and endothermic nature.Additionally,HPS-aerogel showed good anti-interference ability for coexisting pollutant.Importantly,HPS-aerogel exhibited an effective fixed-bed column adsorption performance for dynamic Cu²⁺and CR with superior reusability and stability.Furthermore,HPS-aerogel showed outstanding adsorption efficiencies for Cu²⁺and CR in real samples.The main adsorption mechanism for Cu²⁺was attributed to the electrostatic attraction and chelation,and which was electrostatic attraction,Schiff base,and hydrogen bonding for CR.Therefore,HPS-aerogel should to be a promising adsorbent for removing both heavy-metal ions and dyes from wastewater.