Study On The Adsorption Properties Of Hydroxyapatite On Lead And Its Application In Oyster Sauce

As industrialized process accelerating ceaselessly, lead pollution has penetratedinto all aspects of life. The amount of food polluted by lead has become more andmore large, it has caused great harm to the human beings health. Hydroxyapatite is akind of adsorbent for lead. It has a good adsorption capacity, which can be used toremove lead ion in food. In this paper discarded clam shell has been used as rawmaterial, by the use of chemical precipitation method, under normal temperature tosynthesis hydroxyapatite, then to identify the adsorption and desorption effect insimulated solution, estimate the optimum conditions of adsorption and analyzeadsorption mechanism. After that it has been used to adsorb lead in oyster sauce. Themain contents are as follows:1By the method of chemical precipitation, hydroxyapatite was synthesized fromclam shell under room temperature.To characterize the hydroxyapatite in three kindofmethod:X ray diffraction, Fourier transform infrared spectroscopy and electronmicroscope analysis.The results show thatsynthetic productis small short clavateparticle, with voids in surface. The XRD diffraction peak match with JCPDS09-0432.Infrared spectrum is full of the-OH, PO43-absorption peak. This method has theadvantages of simple process, easy operation, easy control of reaction conditions. Tosynthesis hydroxyapatitefrom a discarded clam not only increase the economic benefit,but also improve the utilization rate of clam, meanwhile avoid the pollution to theenvironment, it is a method can be widely used for the synthesis of hydroxyapatite.2To estimate different factor in the adsorption of lead ion in the solution,different conditions such as the proper contact time, pH value, temperature and initialconcentration of solution has been judged.The adsorption mechanism has beenanalyzed by the kinetics and thermodynamics theory. In the absorption of Pb²⁺, Theresults show that the proper pH is3.0, the acidic environment favorable toabsorptionand high pH minimize the absorption capacity; the adsorption equilibrium can be reached in30min; high concentrate of Pb²⁺is good for adsorption to someextent，and the adsorption is a process of Langmuir adsorption isotherms, followingthe pseudo-second-order kinetic equation. The thermodynamics of the processindicates an endothermic sorption process of Pb²⁺.3To test the effect of application, hydroxyapatite has been used to adsorb leadion in oyster sauce. To detecte the lead concentration in the adsorbed hydroxyapatiteand the filtrate respectively, the results show that the adsorption rate is basically thesame, the adsorption rate is higher than98%. The main physical and chemical indexesof oyster sauce do not change after adsorption, hydroxyapatite does not affect thequality of oyster sauce.The method used in this paper to synthesis hydroxyapatite get a good effect. Thematerial has a very well adsorption effect, and it is difficult to take off adsorption,does not cause secondary pollution. The desulphurization rate oflead in oyster sauce isabove98%, do not affect oyster sauce quality, this material can be used to removelead in a liquid food and health products. So synthesis hydroxyapatite from theabandoned clam shell is a simple, easily control and lowly cost method. It is not onlymake full use of the clam, but also reduce the environment pollution.