Adsorptive Removal Of Phosphate In Wastewater By Layered Double Hydroxides

As a result of phosphorus and other nutrients persistently discharge,resulting in eutrophication of water,a large number of algae in the water body,dissolved oxygen decreased,water quality deterioration,serious damage to ecological environment.Phosphorus entered into the water environment in the main way of phosphorus-containing industrial wastewaterv and life sewage discharge.Therefore,effectively remove the phosphorus in front of sewage and wastewater discharge which is an important means of controlling water eutrophication.As the adsorption method has the advantages of simple operation,high efficiency,low consumption,low pollution and recyclable,it has become a focus of phosphorus removal research at home and abroad.Hydrotalcite is a typical anionic adsorbent that has a unique advantage in wastewater treatment.X-ray diffraction(XRD),Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR),Specific surface area analyzer(BET)and potential analyzer(Zeta)were used to characterize the adsorption.The adsorption mechanism of research and applied to the simulation of phosphorus adsorption in aqueous solution.The main contents of the experiment were as follows:(1)In this paper,four different types of binary X/Al-LDHs(X,Mg,Zn,Ni,Co)samples were prepared by changing the interlayer divalent cations with simple and inexpensive hydrothermal method.The results showed that the adsorption rate of Zn/Al-LDHs was the best at 25 ? and initial pH = 6,the removal rate of phosphate was 92%,the adsorption capacity was 24.965 mg P/g,the adsorption kinetics and the adsorption isotherm is consistent with the pseudo-second-order kinetics equation and the Langmuir equation.The adsorption thermodynamics study shows that the adsorption of phosphorus in the four kinds of hydrotalcite is endothermic and spontaneous process.The adsorbent recycl three times and the removal rate is over 60%.(2)One step closer to study the Ni/Co binary hydrotalcite with different trivalent cations.Ni/Co-C-LDHs are synthesized by hydrothermal method.Swap the interlayer anion of hydrotalcite and preparation of Ni/Co-N-LDHs by Coprecipitation Method.The adsorption mechanism was studied by analyzing the characterization and adsorption properties of the adsorbent.The specific surface area of Ni/Co-N-LDHs is 288.2683 m2/g,which is conducive to the adsorption reaction.The results showed that the removal rate increased to 98% and the maximum adsorption capacity was 49.78 mgP / g at 25 ? and pH = 6.The adsorption kinetics conforms to the pseudo-second-order kinetics equation and proves that it belongs to the chemical adsorption process.The adsorption isotherm agrees with the Langmuir equation,indicating that the adsorption process is monolayer adsorption.Thermodynamic studies have shown that phosphorus adsorption experiments are endothermic and spontaneous.The adsorption mechanism is mainly ion exchange,including the surface adsorption process.Ni/Co-N-LDHs recycling 3 times,the removal rate is still more than 75% and have a good reproducibility and stability.