Study On The Characteristics And Mechanism Of Uranium Wastewater Treatment By Powder Sludge

The utilization and development of nuclear energy not only brought huge benefits,but also brought the nuclear environmental issues. How to effectively deal with theradioactive pollution from the production of nuclear industry, especiallyuranium-containing wastewater, has become a hot issue in present research. Sludge isa self-immobilized body of many microorganisms. On its surface, there are manyactivity groups such as hydroxyl, carboxyl, amino etc. It cans adsorb heavy metals bycovalent bonds, van der Waals force, complexation or chelation, and have severaldisadvantages including big surface area, porosity, stability and good settlingperformance. Therefore, it has been widely attended by scholars in recent years.In this paper, Characteristics and mechanism of uranium(Ⅵ) by activated sludgeand anaerobic granular sludge have been studied, respectively. The residual activatedsludge from an urban sewage treatment plant and anaerobic granular sludge from apaper mill were used to prepare powdered activated sludge (PAS) and anaerobicgranular sludge (PAGS) of biosorbents. Different experimental parameters such assolution pH, adsorbent dose, initial concentration and contact time were examined toinvestigate their effects on absorption of uranium. The adsorption mechanism wasstudied by model simulation, scanning electron microscope, energy-dispersivespectrometry, ion exchange experiment and infrared spectroscopy.The results of biosorption of uranium(Ⅵ) on PAS showed that the maximumadsorption occurs at pH of3, the adsorption reaches equilibrium within120min andthe removal rate was up to97.77%for initial U(Ⅵ) ions concentration of10mg/L.The equilibrium data fit well with the pseudo-second-order model(R2≈1) andFreundlich model(R2≈1). Ion exchange experiments and EDS analysis verified thation exchange was the main adsorption mechanism with Ca2+as the main exchangeion．FTIR spectra before and after PAS adsorbed uranium indicated that its structurewasn ’t change．The used PAS can be desorbed by0.1mol/L HCl (the first desorptionrate is up to92.83%) and became reusable. PAS is nontoxic and eco-friendly, which have a good prospect in the treatment of uranium-containing wastewater.The results of biosorption of uranium(Ⅵ) on PAGS showed that the maximumadsorption occurs at pH of6, adsorbent dosage of2.0g/L and contact time of60minfor an initial U(Ⅵ) ions concentration of10mg/L and30℃. The equilibrium data fitwell with the pseudo-second-order model (R2≈1) and Freundlich model (R2>0.94).SEM photos, EDS analysis and ion exchange experiments verified that ion exchangewas the main adsorption mechanism with Ca2+as the main exchange ion. FTIRspectra showed complexation was also one of the adsorption mechanisms with–OH,C=O, Si–OH,–NH2as the major functional groups involved．The used PAGS can bedesorbed by0.1mol/L HCl (the first desorption rate is up to99%) and becamereusable. PAGS is nontoxic and eco-friendly, which have a good prospect in thetreatment of uranium-containing wastewater.