Prepration Of Tin(IV) Hydrogen Phosphate And Application In Removing Heavy Metals From High Salinity Wastewater

Freuquent heavy metal pollution events have made it a major environmental problem inthe whole society. Owing to the merits of smaller investments, easy to operation, high selectiveadsorption, no secondary pollution, adsorption has become a common method for the removalof heavy metal in waste water with moderate and low concentration. However, the adsorptionprocess is affected by coexisted ions in high salinity waste water and traditional adsorbentshave poor adsorption capacity. Aiming to this problem, study to explore new inorganic andefficient material was conducted in this dissertation. Study on the adsorption property andmechanism with tin(IV) hydrogen phosphate (abbr. SnP) is rather incomplete and study on thefixation and its application has never been reported.In this dissertation, crystalline and amorphous SnP were synthesized by modifiedhydrothermal method and liquid-phase precipitation method, respectively. Batch experimentswere used to examine the adsorption property for Pb(II), Cu(II), and Zn(II) at single ion system,binary ions system, and ternary ions system, respectively. Multiple detection techniques, XRD,SEM, TEM, FT-IR, TG, and specific surface area, were employed to characterize the sampleand understand the surface chemistry. Mechanism of heavy metal removal by SnP wasinvestigated by thermodynamics analysis and potentiometric titration along withabove-mentioned methods. The immobilization of amorphous SnP was conducted andexperiments were carried out in salinity water to investigate the adsorption property. Mainresults were given as follow:The selective adsorption sequence is Pb(II)>Cu(II)>Zn(II), either by crystalline SnP oramorphous SnP, which is relative to hydratation heat of heavy metal ions. The main adsorptionmechanism is ion exchange. These two materials all exhibited favorable behavior in highsalinity media. The material used can be regenerated by dilute HCl solution. However,amorphous SnP presented much better adsorption property than crystalline one, activatedcarbon, and several ion exchange resins. The reason for this phenomenon may lie in the largespecific surface area (four times larger than crystalline SnP), less acting force of hydrogen atom,and larger free degree.The amorphous SnP loaded on the diatomite is170mg/g. The total pore volume andspecific surface area of diatomite both decreases greatly after the loading. The equilibrium datafollows Freundlich model well. The main adsorption mechanism is chemical sorption.Intra-particle diffusion is the reaction rate control step when adsorbing Pb(II). The adsorptionamount is13.9mg/g,3.75mg/g, and3.74mg/g under the conditions of initial concentration50 mg/L and volume50mL in the media of0.6mol/L NaCl solutions. The composite material canbe regenerated with HCl solution and so has the potential for the practice of heavy metalsequestration in high salinity media.The amorphous SnP loaded on the macro-porous silica gel is92.6mg/g. In the columnadsorption, the breakthrough time is30.55h,6.17h,4.9h, and corresponding adsorptioncapacity was10.4mg/g,2.88mg/g,2.47mg/g, for Pb(II), Cu(II), and Zn(II), respectively underthe conditions of initial concentration50mg/L, adsorbent mass2.0g (corresponding bed height5.3cm). The material after column adsorption can also be regenerated, while the adsorptionproperty will be subjected to declination by a small margin. The breakthrough time predictedwith Yoon-Nelson and BDST model can serve as a reference in actual operation.Amorphous SnP-SiO2composite prepared by gel-sol method in-situ possesses large specificsurface area (513m2/g) and abundant pore. The load amount is96.4mg/g, slightly larger thanthat of amorphous SnP loaded on the macro-porous silica gel. Adsorption behavior followsFreundlich model well. The main adsorption mechanism is chemical sorption. In the fresh watermedia, the breakthrough time is39.85h,10.07h,5.45h for Pb(II), Cu(II), and Zn(II),respectively under the conditions of initial concentration4.5mg/L, adsorbent mass1.0g(corresponding bed height2.7cm). In the media of artificial sea water, the breakthrough time is5533min,8330min, and22min. These results demonstrate a new material with excellentadsorption property and bright future for the potential application in sequestering heavy metalsin high salinity waste water.*There are115figures,41tables, and246references.