Study On The Adsorption Of Pb²⁺ And Sr²⁺ In Water By Urea-Formaldehyde Chelating Resin

In this paper, the urea-formaldehyde chelating resin adsorption of Pb2+and Sr2+in water has been studied. Under the condition of the strong shearing and the constant temperature oscillation, the urea-formaldehyde chelating resin adsorption performance of Pb2+and Sr2+is compared. The reduction of urea-formaldehyde chelating resin has been studied, the conclusions are as follows:(1) the molar ratio of formaldehyde and urea (The F/U molar ratio) and the reaction time of polycondensation arc the major influence factors of adsorption. As the F/U molar ratio increaseing, and the reaction time ranging, the adsorption effect of urea formaldehyde resin is reduced. The urea-formaldehyde resin that have the F/U molar ratio of0.8and the reaction time of60min, the removal rate for Pb2+and Sr+can reach99%and80%, respectively.(2) The adsorption of urea-formaldehyde chelating resin for Pb2+and Sr2+is an endothermic process. The resin adsorption isotherms of Pb+and Sr+have a good relevance with the Langmuir equation. The infrared spectrum analysis shows, such as-NH-, NH2,-OH, C=O and C-O-C and other groups, the absorption peak position of these structures of urea-formaldehyde chelating resin are all shifted after the reaction with Pb2+or Sr2+compareing with the absorption peak position of these structures before adsorption, this phenomena shows that the resin and metal ions are reaction by chelation.When the concentration of the H+is high to0.1mol/L～1.5mol/L, the resin still has a good absorption effect to Pb2+and Sr2+(3) Under the condition of constant temperature oscillation, the urea-formaldehyde chelating resin dosage is8.0g in per100mL water, the initial pH of water is3.0, reaction time is24hours, the removal rates of Pb2+and Sr2+are99.73%and86.52%respectively.(4) Under the condition of strong shear, Shearing time is25min, the removal rates of UF resin for Pb2+and Sr2+are99.96%and88.71%respectively, and the reaction time is much shorter.The scanning electron microscope (SEM) observation shows that the size of the particles of urea-formaldehyde chelating resin are2-5times smaller than the size of the particles under the condition of constant temperature oscillation.(5) The differential scanning calorimetry (DSC) shows that the urea-formaldehyde chelating resin decomposition can be divided into three phases, evaporation stage, fast pyrolysis stage and the calcined stage. Adding ammonium nitrate and increasing the acidity of the system can promote the decomposition of urea-formaldehyde chelating resin.The time of the complete decomposition is about4h.