| With the development of economy and society,environmental problems have became more and more serious,one of which is the lake eutrophication,it has seriously affected people’s quality of life and threatened the integrity and safety of the ecosystem.Because the phosphorus is the key factor which causes the lake eutrophication,so the removal of excess phosphorus in water is an effective means to control the lake eutrophication.A lot of methods to remove the phosphorus have been studied,but adsorption is an important direction in removing the phosphorus in wastewater due to its high adsorption capacity,high removal rate and low cost.Magnesia has been proved to be an adsorbent which has larger surface area and many porosity,high adsorption capacity,cheap price,and it has attracted much attention,but due to the size of Magnesia is too small,its application in water treatment is limited.In order to obtain better practicability in water treatment and better phosphorus removal effect,we use the pectin to modify Magnesia.In this paper,a series of experiments had been conducted to get the optimum conditions for the preparation of MgO/pectin composite adsorbent.Results showed that the optimal ratio of MgO to pectin is determined as 3:1,and the optimum calcination temperature and time were 400℃ and60 min.At the same time,this paper carried out a series of parallel experiments for phosphorus removal using MgO/pectin composite adsorbent and MgO,the results proved that in ever unit quality of adsorbent,MgO/ pectin composite adsorbent had higher phosphorus adsorption capacity than MgO,and experiments show that the pectin basically has no adsorption for phosphorus,and the modified adsorbent is more easily precipitating and separated from water.When the initial concentration of phosphorus is20mg/l,ratio of adsorbent to liquid was 1g/l,MgO/ pectin composite adsorbent can achieve adsorption equilibrium at 120 min,the equilibrium adsorption capacity was 19.3mg/g;when the pH changes in 2~9,MgO/ pectin composite adsorbent can still maintain a high adsorption capacity.Environmental scanning electron microscopy(SEM),X ray diffraction scanning(XRD)and Fourier transform infrared spectroscopy(FT-IR)were used in the experiment to study surface characteristics of MgO/pectin composite adsorbent;Furthermore,the analysis of thermodynamics and kinetics indicate that the Langmuir isotherm adsorption model is more suitable to describe the adsorption process of the composite adsorbent than the Freudlich isotherm adsorption model;the pseudo-second-order model is more suitable to describe the process of composite adsorbent for phosphate adsorption.Whilst,due to0(35)G <0,0(35)H >0,0(35)S >0,it showed that the spontaneous and endothermic in nature was involved in phosphorus removal process.It is concluded that the MgO/pectin composite adsorbent modified by pectin not only shows a high phosphorus removal capacity,but also improves practicability of the adsorbent in water treatment. |
