| An adsorbent was first prepared from used hot pack for dephosphorization.And then,the main physical and chemical properties was confirmed by XRD,FTIR and Elemental analysis. BET surface area, average diameter and point of zero charge were determined. After that,its adsorption isotherms, thermal and kinetic parameters were observeded.And on this basis, the laws of interaction between pH,adsorption properties and zeta potential were investigated for the mechanism of the phosphate adsorption. At last, actual phosphorus wastewater was used to verify its ability to deal with the actual wastewater. The detailed specific conclusions about thesis are as follows:(1)Main physical and chemical properties:Chemical element analysis shows that t-he adsorbent preparation of the main chemical composition for iron elements, includin-g a small amount of Si, Al, Mg. BET surface area, average diameter and point of zer-o charge were determined, the results were98.3m2/g,510nm, and pH5.7respectivel-y. The adsorbent was confirmed to be Magnetite-Goethite Mix phase (MGM) by XR-D, FTIR and Elemental analysis. The sorbent had the surface hydroxylation characteris-tics. Surface zeta potential analysis found that the adsorbent for variable charge surfa-ce,when pH is high, positive charge of adsorbent surface could be achieved; pH is sm-aller,charge of sorbent surface is negative.(2)Research of adsorption behavior showed that when the initial solution pH for2, as from15℃temperature increased to40℃, the maximum phosphorus adsorption qu-antity (qm)from10.53mg/g increases to13.35mg/g. The adsorption isotherms of p-h-osphorus fit Langmuir equation well, and the time-resolved curves of phosphorus ads-o-rption on MGM follows pseudo-second-order kinetic model. Initial adsorption rate as t-he reaction temperature rose from6.74to8.22mg/(g·h).This revealed that with the in crease of temperature, the adsorption of phosphorus was promoted. Thermodynami-c pa r-ameters of phosphorus adsorption on the MGM surface showed that the adsorpti-on pr-ocess is spontaneous, endothermic, and phosphorus in solution preferentially selec-tiv e adsorption on the MGM.(3) The study of adsorption mechanism found that phosphorus adsorption quantity decreased with the solution pH value increasing. When initial pH value between2-7, final pH would elevated at different degree after reaction. This change was the characteristics of hydroxyl release.Growth of pH could baffle transformation outer-sphere complexes to inner-sphere complexes.The pHIEP of MGM was5.7,however it would have been a marked shift to the left after adsorption. Shift to the left was the evidence of anionic obligate adsorption,in other words, the evidence of inner-sphere complexes. In the system of phosphorus, pH-zeta curve of MGM Showed a sharp decline at first,and then followed by a gradual decline.That change trend was lead by transition adsorption behavior. When pH=2/6, changes in ionic strength has little effect on the removal rate of phosphorus.But when pH=10, phosphorus removal rate increases with ionic strength upward. This also showed that as the pH increases, the phosphorus removal was influenced by the ionic strength enhanced. Color experiment of Fe3+and SCN-showed formation of surface direct precipitation. Studies also indicated adsorption of phosphorus on the adsorbent was dominated by the solution pH.Inner-sphere adsorption,electrostatic attraction and direct precipitation jointly promoted adsorption of phosphorus at low pH. Inner-sphere adsorption and electrostatic attraction decreasesd with the increase of pH. However, the phenomenon of inner-sphere adsorption from co-adsorption and indirect precipitation were observed as rising of pH. The decline of phosphorous removal obtained from the combined effects at high pH.(4) the actual wastewater by adsorption experiments show that:when the actual w-astewater solution pH=2, MGM’s dosing quantity for10g/L, the removal rate can reach94.16%, at the same time to illustrate MGM suitable for processing low pH hig-h phosphorus wastewater. |
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