HFO Adsorption Mechanism Study Of Cd Based On PHREEQC

While the mining industrial cities were made great contribution to the nationaleconomy, we have to face the threat from the environment. Wastewater produced bymine through various channels of nature into the soil and surface water environment,which makes the Water pollution become the bigest threat in mining cities. There aremany ways to control the heavy metal over standard in surface water. One of the mostcommon way is to use the Adsorption Reagents, such as HFO（Hydrous ferricoxide）.As a kind of good adsorbent numerous scientific research workers have beenmany studies around it, and are used in many fields.In the use of HFO to deal withindustrial waste water and water polluted with heavy metals Cd, often only payattention to the macro application effect, because in a real environment, the ioncontent of natural water body is complicated, the change of water environment oftenmake HFO have impact on heavy metal Cd adsorption ability.The practicalapplication and practice of the theory of light tend to study limitations adsorptioncoprecipitation.Integrated a lot of research data in this article on the basis of the basiccharacteristics of HFO made a summary.Using the method of oxidation kinetics ofstable HFO in solution to form the time required for the simulation.HFO adsorptionprinciple elaboration, introduced specifically used to describe the diffusion layer HFO(double) model.Finally with west panzhihua checks the river as an example, usingPHREEQC software in the diffusion layer model of simulated HFO Cd adsorptionability of heavy metals in water.The concrete research content is as follows:(1) HFO for pollutants adsorption is mainly affected by pH and ionic strength ofsolution and the size of the organic material concentration control.PH change makeHFO surface electrical changes, the changes of ionic strength will increasecompetition between adsorption sites, the changes of organic matter concentrationelectronegative in aqueous solution.But in theory the adsorption mechanism of HFOmainly by forming coordination complex or electrostatic interactions.HFO fromforming on the length of time is divided into stable and unstable type two kinds, bothon the adsorption effect have very big difference, in order to make new HFO hasstronger stability in laboratory research on HFO load.(2) The solution of iron ion may be two kinds of reaction process, one kind israpidly hydrolyzed to form iron oxide hydrate after settling.The other is a low state ofiron ions in under the action of oxidant slow oxidation of high state of iron ions, andthen quickly hydrolysis precipitation in aqueous solution.Either as a result, theprecipitation of material after a period of time in different environments will form HFO.In order to explore the formation of stable HFO time, this paper is simulated byusing the method of oxidation kinetics research.Results show that iron oxidationkinetics follows the principle of conservation of mass, in alkaline aqueous solution ofenvironment, if sufficient oxygen under the condition of Fe2+oxidation into Fe3+it onlytakes a few minutes.However, the generated Fe3+will be combined with the water OH-,form deposits of iron, reduce the pH in the solution.While the oxidation rate dependson the activity of hydroxyl ions size, with the reduction of pH oxidation rate isirregular linear decrease.(3) adsorption study can be divided into two categories, experimental research andsimulation, simulation research and can be divided into empirical model andmolecular model.Including molecular model in the support of new technology anddeveloping rapidly under the gradually perfect of thermodynamics database.Thedouble electrical layer model of diffusion respectively on the model the effect of pHon the adsorption results in the process and the density of the site are defined, modelhas been widely recognized.PHREEQC software developers by double electrical layermodel of diffusion for HFO adsorption process, a new module embedded intoPHREEQC software.PHREEQC software in the equilibrium state of the new moduleand absorption boundary conditions are defined and then through a lot of experimentsand software simulation results are coupled, the thermodynamic database forcorrection.Therefore, this paper argues that PHREEQC software with the doubleelectrical layer model of diffusion can make good forecast to Cd adsorption of heavymetals.Will bring PHREEQC software model applied to west panzhihua checks of thesimulation results are as follows:(4) in order to explore the migration characteristics and physiological toxicity ofheavy metal Cd, speciation analysis on heavy metal Cd simulations we concluded thatthe heavy metal Cd in GuanHe sample collection period mainly in the form of Cd+2and CdSO4is given priority to, of the total accounted for45.30%and32.79%respectively.The two forms are conducive to a Cd.Influence on the formationdistribution of pH value on Cd, in acidic environment and weak alkaline environmentconducive to Cd migration, will form the solubility in alkali environment CdCO3smaller substances, is not conducive to a Cd.Because of the heavy metal Cd’soutermost only lost two electrons, so pE value change had no obvious effect on theformation distribution of Cd.Also leads to increased concentration of SO42-free stateof Cd+2, CdSO4content increased, the heavy metal Cd in water migration will morecontrolled by hydrodynamic.(5) the simulation results show that the diffusion layer to control the water samplecollection period of HFO heavy metal Cd adsorption efficiency reached86.22%, remaining Cd content in water was only1.378ppm, far lower than the nationalstandard of0.005mg/L, the treated water quality reach the national standard.HFO forCa+2, the adsorption effect of Cu+2are stronger than the Cd+2.If Ca+2and Cu+2contentis too high will affect the adsorption effect of Cd, but on the other hand add HFOavailable in water to soften the hard water at the same time dealing with other types ofheavy metal elements.Has enormous influence on the effect of pH on Cd adsorption,with the pH value increased gradually of HFO adsorption capacity of heavy metal Cdgradually strengthen, natural surface water environment is conducive to HFOadsorption of heavy metal Cd, result in accordance with the experimental research inthe literature.But the increase of SO42-concentration in water body will heightencompetition adsorption sites results in the decrease of absorption ability a linear trend.Comprehensive the above results, HFO can be applied to west panzhihua controlin water treatment.