Simultaneous Adsorption Characteristics And Mechanism Of PAFC And CMC Functionalized Sludge-based Carbonized Materials For Cd（Ⅱ） And SDBS In Electroplating Wastewater

The presence of both heavy metals（e.g.Cd（II））and surfactants（e.g.sodium dodecylbenzene sulfonate,SDBS）in electroplating wastewater is not only difficult to treat,but also poses a serious threat to human health and the environment.In this thesis,we propose to use the residual sludge of waste water plant as raw material and prepare adsorbent material with excellent adsorption performance by carbonization method and modification of polymerized aluminum chloride iron（PAFC）and carboxymethyl chitosan（CMC）,and adsorb heavy metal Cd（II）and organic pollutant sodium dodecylbenzene sulfonate in electroplating wastewater simultaneously by one-step adsorption method.This is not only a resource utilization of waste sludge,but also an efficient and simple adsorption treatment of wastewater containing multiple pollutants in one step,which achieves the goal of treating waste with waste.The main findings of the related studies are as follows.（1）Four adsorbents（sludge carbonized（SSA）,carbonized modified by PAFC（SSA-P）,carbonized modified by CMC（SSA-C）,SSA-P modified by CMC（SSA-S））were examined for physical morphology（electron microscopy）,specific surface area and pore size distribution,surface functional groups（infrared spectroscopy and Bohem titration）and crystal structure,and other physical and chemical properties.The results showed that the surface physical morphology（electron microscopy）,specific surface area and pore size distribution,surface functional groups（infrared spectroscopy and Bohem titration）and crystal structure of the four adsorbents were examined.The results showed that the surface structure of the four adsorbents showed a rough porous structure due to the transformation of the organic matter inside the sludge into carbon skeleton after carbonization;the specific surface area and pore volume of the modified SSA-P,SSA-C and SSA-S were lower than those of the pre-modified adsorbent SSA,but the surface functional groups（such as carboxyl and hydroxyl groups）were greatly increased,with SSA-S being the most abundant and SSA-P and SSA-S being the most abundant.The SSA-S functional group was the most abundant,followed by SSA-P and SSA-C.The increase in the number of these functional groups contributed to the chemisorption of the pollutants Cd（II）and SDBS.The crystal structure analysis of the four adsorbents showed that silica was the main crystal,while the addition of CMC and PAFC led to the weakening of the overall diffraction peak intensity and the decrease of the crystallinity of the modified adsorbents.（2）The adsorption results of the four adsorbents on a single pollutant（Cd（II）or SDBS）showed that SSA-S had the highest adsorption efficiency,with the adsorption amounts of 111.1mg g-1 and 345.55 mg g-1 for Cd（II）and SDBS,while SSA-P and SSA-C were the next most effective,and only the carbonized SSA had the worst adsorption efficiency.This is due to the fact that the CMC modified with PFCA has more chemical groups that can chemisorption of pollutants by electro-neutralization,bridging and electrostatic interaction.In addition,the results showed that the optimum p H of the four adsorbents for Cd（II）and SDBS was 6 at an adsorption temperature of 25°C and the adsorption equilibrium time was 12 h.Furthermore,the thermodynamic and kinetic studies concluded that the adsorption reaction was a heat absorption reaction;the Langmuir model better described the adsorption of Cd（II）and SDBS by the four adsorbents,indicating that the adsorption process of both pollutants The Langmuir model better describes the adsorption of Cd（II）and SDBS by the four adsorbents,showing that the adsorption process of both pollutants is unimolecular layer adsorption.In addition,the quasisecondary equation could better fit the adsorption processes of the four adsorbents for the two pollutants,indicating that the adsorption of Cd（II）and SDBS on the four species was mainly controlled by chemisorption.（3）In the dual-pollutant adsorption system,the adsorption capacity of the modified optimal adsorbent（SSA-S）for both pollutants was greater than that for the adsorption of a single pollutant;also the adsorption process increased its adsorption of Cd（II）and SDBS by 8%and 19%,respectively,compared to that for single adsorption.In addition to the adsorption mechanism of the adsorbent in（ii）,this is due to the additional synergistic effect of bridging between Cd（II）and SDBS as well as electrostatic interaction（producing precipitation in the form of bidentate）to increase the adsorption capacity of the adsorbent for both pollutants.（4）The regeneration experiments of SSA-S showed that the adsorption of Cd（II）and SDBS still reached 86% and 85% of the initial adsorption capacity after three regeneration cycles,which indicates that the modified sludge-based adsorbent is an efficient adsorption of pollutants and an economical and environmentally friendly water treatment material.