Mhp Adsorbent Preparation And Ammonia Adsorption Properties

At present, comparing with other methods, the MgNH₄PO₄ chemicalprecipitation method has the advantages of simple technology and goodtreating performance, but it has some disadvantages, such as the highreagent cost(magnesium salt and phosphate salt), and the ways to disposethe precipitate of MgNH₄PO₄·6H₂O (MAP) is limited. In this study, wehave suggested a new ammonia removal process by using the MgHPO₄(MHP) as the sorbent. The MHP sorbent could be prepared by thepyrogenation of the MAP, and could be repeatly used.The main task in this article could be divided as follows:The studies on the MAP precipitation process and the preparation ofMAP were carried out. By adding Na₂HPO₄·12H₂O and MgCl₂·6H₂O asthe magnesium salt and phosphate salt, the effects of stiring time, the pHvalue and the Mg: N: P ratios etc were investigated. The MAP precipitatewas prepared at the conditions pH=9, Mg: N: P=1:1:1. The shape andcomponents of the MAP powder were characterized by means of SEM,XRD.By using the MAP prepared as raw material, the MHP sorbent wasprepared by calcining the MAP powder in the electric tubular furnace.The components and shape of the MHP sorbent were characterized bymeans of TGA-DTA, SEM, and XRD etc. And the effects of pyrogenationtemperature and pyrogenation time on the absorption ability of MHPsorbent were also investigated. The results showed that the MHP sorbentprepared at the pyrogenation temperature 90℃～130℃, pyrogenationtime 2～3h had good absorption ability to absorb the NH₃-N in thewastewater.The conditions for the MHP sorbent to absorb NH₃-N were studiedby the orthogonal experiments and the single factor experiments,including the factors such as temperature, pH value, the sorbent dosage,the initial concentration of NH₄⁺ etc. The results showed that the removalrate of NH₃-N from the wastewater of the NH₄⁺ initial concentration900mg/L is above 95%, at pH=9, MHP sorbent added 15g/L. The effect of the temperature was not obvious, and this process was suitable for thetreatment of high concentration NH₃-N wastewater.The studies of MHP asorption method to repeatly treat NH₃-N in thewastewater were carried out. In the circuiting experiment, using theprecipitate produced in the MHP adsorbtion process as the raw material,the adsorption efficiency of MHP sorbent used repeatly was investigated.The results showed that the removal rate of the NH₃-N was still above70% after 5 cycles without additional magnesium salt and phosphate salt.Because ammonia could be recovery and reused in MHP absorptionprocess as high concentration NH₃·H₂O solution, the MHP sorbent couldreuse by regeneration, and the consumption of medicament was low. Sothe process is possible to solve the problems of the cost and taking gooduse of MAP, which were the two main problems of MAP chemicalprecipitation method. This MHP adsorption process could become aneconomical and effective method.