Study On The Preparation Of Inorganic Porous Material And Its Adsorption Characteristics And Mechanism For Low Concentration Hexavalent Chromium In Wastewater

Chromium is one of the major heavy metals on the earth.In industries such as electroplating,tanning,sodium,and potassium chlorate production,it usually exists in industrial wastewater in a highly toxic hexavalent form(ie,Cr(?)).If the hexavalent chromium in natural water exceeds the environmental limit,it will pose a huge threat to human health and the ecological environment.Therefore,wastewater containing Cr(?)should be treated before discharge.Among many treatment methods,adsorption shows high practical value because of its excellent characteristics such as high efficiency and low cost.In this study,a new type of zeolite with surface adsorption was successfully synthesized by modifying 4A zeolite with HACC.It was used to adsorb trace chromium in aqueous solution,and its structure and adsorption mechanism were analyzed in detail.The results showed that the surface modification does not destroy the excellent pore structure of 4A zeolite,and the surface roughness leads to high hydrophilicity.HACC is evenly distributed on the surface of 4A zeolite and each amino site of HACC has adsorption characteristics.The results of adsorption behavior show that the adsorption efficiency of modified adsorbent for low concentration Cr(?)is as high as 92%,significantly higher than that of each component alone.Thermodynamic and kinetic parameters show that the removal process is spontaneous,exothermic and pseudo second-order chemisorption.At the same time,in response to the call of national circular economy,aiming at the harm to the environment caused by the solid waste paper-making sludge produced in the production of paper mills,in this study,the paper sludge rich in organic matters was used to prepare the active carbon(ps AC)with excellent specific surface area and rich oxygen function group,so as to further purify the wastewater containing Cr(?)and achieve the purpose of"treating waste with waste".The results of batch experiments showed that the change of p H value will not lead to the significant decrease of Cr(?)removal rate under acid condition.The maximum adsorption capacity of ps AC is 54.04 mg g^-1.The enthalpy of adsorption is 17.37 k J mol^-1,indicating that the chemical selection process is controlled by hydrogen bond,which has also been verified by some analytical techniques.Finally,this study also provides a way to reuse the waste ps AC of Cr(?)in furfural hydrogenation.