Fabrication Of Graphene-based Aerogel Beads And Its Adsorption Mechanism Of Cu²⁺

At present,the deep removal of the low concentration heavy metal ions is always the key issue in wastewater treatment field.Adsorption method,because of its high efficiency,economy and environment-friendly,is widely used to deeply remove heavy metal pollution.Graphene oxide?GO?has been widely used in adsorption materials by researchers at home and abroad,owing to its large specific surface area and abundant oxygen-containing functional groups.But the powder-like graphene oxide adsorbent is easy to lost and difficult to recover,which seriously limit the application in practice.Therefore,it has a great scientific research and practical application value to accurately identify and process the oxygen-containing groups in graphene oxide,and design the powdered graphene oxide into molding adsorption materials with a 3D spatial network structures through the molecular bridging.Sodium alginate?SA?is an important intermediate in the preparation of molding materials,and is also an environmentally friendly natural carbohydrate,and,the molecular chain of SA contains a large number of carboxyl and hydroxyl groups,which can be crosslinked with Ca²⁺to form hydrogels.Hence,a new type of GO-based aerogel beads with GO and SA?as matrix?were prepared by chemical crosslinking and freeze-drying technology in this work,which realized functional complementarity between different materials and identified the interaction of various groups in spatial configuration.The spatial structure and properties of GO-based aerogel beads were further designed by introducing titanium dioxide and montmorillonite nanoparticles,and the adsorption mechanism of the different GO-based aerogel beads on Cu²⁺was investigated.The details are as follows:1)A porous structured GO/SA aerogel beads with GO and SA as raw materials were formed by hydrogen bonds with C=O,-O-,-OH and-COOH as well as cross-linking of COO^-and Ca²⁺.Adsorption experiments show:the adsorption process of Cu²⁺by GO/SA aerogel beads was mainly chemical adsorption and multilayer adsorption.Hydroxyl,carboxyl groups and electrostatic attraction were involved in adsorpting of Cu²⁺with the maximum adsorption capacity can reach to75.49 mg/g.2)On the basis of 1),titanium dioxide?TiO₂?nanopowders were introduced to form GO-TiO₂/SA aerogel beads with a 3D network structure by ion bridge of COO^-and Ca²⁺,chemical cross-linking?C-O-Ti bond?,and hydrogen bonds with C=O,-O-,-OH and-COOH.Compared with GO/SA aerogel beads,the specific surface area increased from 85.18 to 133.40 m²/g and the maximum adsorption capacity reached90.91 mg/g.The adsorption process of Cu²⁺by GO-TiO₂/SA aerogel beads was mainly chemical adsorption and monolayer adsorption.3)On the basis of 1),a 3D network-structured GO-MMT/SA aerogel beads were formed by ion bridge of COO^-and Ca²⁺,chemical cross-linking?Al-O-C bond?,and hydrogen bonds with C=O,-O-,-OH and-COOH after the introduction of MMT.The specific surface area of aerogel beads increased to 266.30 m²/g and the maximum adsorption capacity reached 112.78 mg/g.The adsorption process of Cu²⁺by GO-MMT/SA aerogel beads was mainly chemical adsorption and multilayer adsorption.The specific surface area and stability were superior to that of GO/SA and GO-TiO₂/SA aerogel beads.GO/SA aerogel beads with good adsorption ability and stability have been successfully prepared in this work,which solved the problem of powder adsorbent difficult recovery and easy loss,and the preparation process of aerogel materials with large specific surface area and stable mechanical properties was obtained.This study provides an effective method for the molding of powder nanomaterials and treating of low concentration copper-containing wastewater and which has a great research significance.