Research And Development Of Iron And Calcium Based Layered Double Hydroxides For Efficient Removal Of Cr(Ⅵ) From Aqueous Solutions

Industrial pollution,especially heavy metal pollution,has caused great damage to the environment with the continuous acceleration of the process of industrialization in China.Chromium（Cr）has high toxicity and carcinogenicity,which causes serious pollution to soil,water resources and atmosphere.At present,the control of chromium pollution is the top priority for environmental protection departments and related enterprises.Layered double hydroxiedes（LDHs）are a kind of anionic clay and has some properties,such as alkaline,thermal stability,interlayer anion exchangeability,memory effect and adjustable two-dimensional pore structure because of their unique structure.This makes it widely used in ion exchange,water treatment,catalyst,adsorbent,flame retardant material and etc.In this dissertation,the CaAl-LDH,FeAl-LDH and their modified materials were prepared and used to remove Cr（Ⅵ）from aqueous solution.The main contents and results were:（1）Two kinds of hydrotalcite nanomaterials CaAl-LDH and FeAl-LDH were prepared by hydrothermal method using common Ca,Fe and Al salts as raw materials and used to adsorb Cr（Ⅵ）from aqueous solution.The results showed that CaAl-LDH and FeAl-LDH had typical characteristic diffraction peaks of hydrotalcite.The adsorption process was almost not affected by the initial p H of the solution.Moreover,the co-existing anions in the solution had little effect on the adsorption capacity.The adsorption process of Cr（Ⅵ）by CaAl-LDH and FeAl-LDH was fast and reached equilibrium at 30 min.The theoretical maximum adsorption capacities were 34.92 and 51.31 mg/g,respectively.（2）CaAl-LDH and FeAl-LDH were modified by PPy.The adsorption experiments were performed using Ppy,CaAl-LDH-PPy and FeAl-LDH-PPy for aqueous Cr（Ⅵ）.The results showed that CaAl-LDH-PPy and FeAl-LDH-PPy had typical characteristic diffraction peaks of hydrotalcite.The initial p H value and coexisting ions have little effect on the adsorption of Cr（Ⅵ）.The adsorption process of Cr（Ⅵ）by CaAl-LDH-PPy and FeAl-LDH-PPy reached equilibrium at 60 min.Moreover,the theoretical maximum adsorption capacities were 42.21and 172.4 mg/g,respectively.Besides,FeAl-LDH-PPy could be used in real water samples,and the adsorption capacity was above 70 mg/g.Ca²⁺and Fe²⁺were used as divalent metal ions to synthesize the hydrotalcite functional materials in this study.At the same time,PPy was used to modify it.This can provide some train of thought,for the treatment of heavy metals by hydrotalcite functional materials.In addition,it also provides a kind of efficient functional materials for the treatment of wastewater containing Cr（Ⅵ）.