Study On Adsorption Of Contaminants From Water By Using Lanthanum Modified Blast Furnace Slag

Blast furnace slag is an industrial waste from steel plant,which has a certain specific surface area and adsorption capacity.In this study,blast furnace slag was used as raw material,and modified by rare earth element lanthanum via an ion exchange method to prepare lanthanum modified blast furnace slag?La-modified blast furnace slag?.Scanning electron microscopy?SEM?,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FTIR?and Energy dispersive X-ray?EDX?spectrometer were used to characterize the modified adsorbent.Adsorption of tetracycline and phosphate were studied.The results are presented as following:Firstly,La-modified blast furnace slag was used to adsorptively remove tetracycline.Compared with the raw blast furnace slag,the adsorption capacity of La-modified blast furnace slag for tetracycline increased by 90.1%.Neutral and weakly alkaline conditions were beneficial to the adsorption and removal of tetracycline by La-modified blast furnace slag.Removal efficiency for tetracycline increased with the increasing adsorbent dosage.The coexisting aions including Cl^-,NO₃^-,SO₄^2-,HCO₃^-could promote the adsorption of tetracycline by the adsorbent,while HPO₄^2-could inhibit the adsorption.Presence of natural organic matter?humic acid?increased the adsorption capacity.Adsorption kinetics experiments showed that the adsorption of tetracycline well followed pseudo-second-order kinetics model and Elovich model,indicating that the adsorption mihgt be chemisorption with diffusion control mechanism.The adsorption isotherm of tetracycline adsorbed by La-modified blast furnace slag gradually became linear with an increase of tetracycline concentration.For phosphate adsorption,the adsorption capacity by the La-modified blast furnace slag increased by 170.0%compared with the raw blast furnace slag.Weakly acidic condition was beneficial to the adsorption of phosphate.The maximum tetracycline uptake was observed at pH 5.0,and the adsorption capacity achieved 11.94 mg/g.The removal efficiency for phosphate increased with increasing adsorbent dosage.Coexisting anions such as Cl^-,NO₃^-,SO₄^2-,HCO₃^-had an inhibitory effect on the adsorption process,while the inhibition increased with the increasing concentration of coexisting ions.Humic acid in water had a significant inhibitory effect on phosphate adsorption.Linear pseudo-second-order kinetics model and Elovich kinetic model can better describe the adsorption of phosphate by La-modified blast furnace slag,indicating that there were simultaneous chemical adsorption and diffusion control mechanisms in the adsorption process.It can be observed from the fitting parameters of the Langmuir model that the adsorption capacity for phosphates decreased as the adsorption temperature increased,which proved that the adsorption process was an exothermic process.From above,the La-modified blast furnace slag had good adsorption capability for tetracycline and phosphate,and application in practical water treatment process is highly anticipated.