Study on adsorption behavior of fluoride ion by desiliconization sludge from waste acid
In this paper,the fluoride adsorbent manufactured by the desiliconized sludge produced from the purification process of waste acid from steel plate surface cleaning and its adsorption behavior was studied by X-ray fluorescence spectroscopy(XRF),X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM),X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared absorption spectroscopy(FT-IR).The effects of initial pH value,ionic strength,and coexisting ions on the adsorption process were investigated.The thermodynamics,kinetics,and site energy distribution of the adsorption process were also discussed.The results show that the desiliconized sludge contains a large number of needle-like hydroxy-iron oxide crystals and its Zeta potential value is 6.98.The removal rate of fluoride ions is above 90％when the initial pH value is 2 to 10.The adsorption process is little affected by the ionic strength change and follows an internal complexion model.The co-existing multi-charge anions have much effect on the adsorption and the order of influence from high to low is PO43-,SO42-,NO3-;The adsorption process is consistent with the Langmuir model and the Elovich model,which is a spontaneous exothermic physical monolayer uniform adsorption also including some chemical adsorption.The maximum adsorption capacity according to the fitting of the Langmuir model at 25 ℃ is 5.626 mg/g,and the maximum adsorption capacity according to the test reaches 6.303 mg/g.The adsorption process mainly occurs in the low-energy region according to the energy distribution fitting,and the increase of the temperature increases the adsorption site numbers,especially the high-energy sites.According to the characterization analysis of the desilicated sludge before and after adsorption,the fluoride ion in water is adsorbed by the desilicated sludge mainly involving ion exchange and electrostatic adsorption.
environmental engineeringdesiliconization sludgeadsorptionfluorideenergy distribution
万方数据
维普
