Removal Of Phosphorus From Simulated Eutrophic Water By La-modified Attapulgite

The adsorption of phosphate using clay plays an important role in the treatment of eutrophic water. Australia Phoslock Water Solutions LTD. Company produce a product called PHOSLOCK (lanthanum modified montmorillonite), which is widely used for controlling eutrophication and has a significant effect. Considering the specific production process of bleaching agent of Jiangsu Huida Mining Technology Co., Ltd. Company, we prepared a La-modified acidified attapulgite(La-H-ATP) and a non-acidified attapulgite(La-ATP). We compared the adsorption properties of two adsorbents in different water chemical conditions, and we also analyzed the effect of two adsorbents on sediment phosphate control.We used many means for La-ATP and La-H-ATP detection and characterization, such as scanning electron microscopy (SEM), N2 cryogenic adsorption-desorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence spectrometry (XRF), inductively coupled plasma spectroscopy (ICP), etc. The results show that the attapulgite used in this experiment has a good mineral quality, high crystallinity, clear rod-like structure, and a certain amount of calcium, iron and other impurity ions. The surface area of La-ATP and La-H-ATP is 82.40 m2/g and 107.84 m2/g. XRF and ICP data show that the loading of lanthanum element on La-ATP (22.9 mg/g) is higher than La-H-ATP (8.0 mg/g).Adsorption tests showed that the maximum adsorption capacity of La-ATP was 12.08 mg/g under neutral conditions, and the maximum absorption capacity of La-H-ATP was 12.38 mg/g. High temperature is beneficial to phosphate adsorption for both La-ATP and La-H-ATP. The adsorption equilibrium qe in high-temperature(35℃) are about twice as low temperature(10℃) for the two adsorbents. The adsorption capacity of phosphate for La-ATP is greater than La-H-ATP at different temperatures, when the concentration of phosphate in the solution is certain. Kinetic studies show that the adsorption model of La-ATP and La-H-ATP is suited to pseudo-second kinetic model, and the adsorption rate constant is 0.0415 g·mg-1·min-1and 0.0316g·mg-1·min-1 for La-ATP and La-H-ATP, respectively. The adsorption capacity for La-ATP is slightly higher than La-H-ATP in acidic condition. La-modified attapulgite has a selective adsorption of phosphate, and chloride, nitrate, sulfate, carbonate have little effect on adsorption.With the amount of cover material increasing, it is advantageous for the suppressed of sediment phosphorus release. When the cover material is 52 g/m2, the inhibition of sediment phosphorus release rate is 71.43% and 85.71% for La-H-ATP and La-ATP, respectively. The phosphorus release of sediment reached its maximum level at a concentration of 0.34 mg/L for no covering material experiment in 20 days,at 25 ℃ condition. The inhibition of sediment phosphorus has reached equilibrium in 25 days for La-H-ATP and La-ATP similarly. At this time, the phosphate concentration of overlying water is 0.091 mg/L and 0.042 mg/L for La-H-ATP and La-ATP, respectively.High temperature is beneficial to the release of phosphorus out of sediment. La-ATP and La-H-ATP have a certain inhibitory effect for phosphorus release of sediment at 10℃,25℃,35℃ conditions and the inhibitory effect of sediment phosphorus release for La-ATP are better than La-H-ATP.On the basis of this research, we can know that lanthanum modified attapulgite material used in controlling eutrophication could have a broad application, and industrial production does not require the acid washing process in the preparation of La-modified attapulgite adsorbent.