Synthesization And Adsorption Property Of NaSOD Zeolite Synthesized From Sewage Sludge Incineration Ash

As incineration becoming more widely used as a method of sewagesludge treatment, bottom ash from sludge incineration plant increasedgreatly and the synthesis of zeolite is one of the promising ways for theutilization of sludge bottom ash according to its chemical components. Inthis work, the potential synthese process were proposed, and thesynthesized NaSOD zeolite was characterized by X-ray diffraction,scanning electron microscopy, Fourier transform infrared spectroscopy,and BET. The adsopriton property was also tested based on the methyleneblue （MB） experiments. The main results were as follows:（1） An open system with ordinary pressure was used for thesynthesization of NaSOD zeolite. Bottom ash should be activated byacid-soluble impurity and alkali-molten activation subsequently. Theoptimum pH of acid-soluble impurity pretreatment was pH1, and theright temperature of alkali-molten activation was700℃under the testedconditions. It was also found that the best combination of NaSOD zeolitecrystallization was: n（SiO₂）/n（Al₂O₃）2, with the alkalinity ratio1.5, thecrystallization temperature100℃, and the crystallization time10h.Synthesized product was pure NaSOD type zeolite with a highcrystallinity and uniform size. The crystal was complete sphericalpetaloid and has a good dispersibility, with a BET specific surface area of222m²Â·g^-1and cationic exchange capacity of80.35mmol·（100g）^-1. Thepresent of Fe in the sludge bottom ash results in a goodsuperparamagnetic in the synthesization of NaSOD zeolite.（2） The adsorption properties of synthesized zeolite were tested bythe MB adsorption experiment. Effect of adsorption time, initial pH, zeolite dosage and ionic strength on the adsorption property wasdiscussed, and it was found that the equilibrium adsorption capacity ofthe zeolite increased as pH value increase from2.04to9.16under theequilibrium adsorption time of360mins, and the the maximumequilibrium adsorption capacity reached to23.7mg·g^-1. The biggestgrowth rate of adsorption among was found around the zero point ofcharge. The removal rate of MB increased as the zeolite dosage/MBincreased, while the equilibrium adsorption capacity decreased, since thecation will occupy the adsorption sites of zeolite, and thus reduce the thezeolite equilibrium adsorption amount of MB⁺, and Ca²⁺has greatereffects than that of Na⁺and K⁺.（3）The adsorption process of MB by NaSOD zeolite fits theLangmuir non-linear adsorption fitting greatly; kinetic research showedthat the adsorption was in line with quasi-second-order kinetic model;results of the intraparticle diffusion model showed that the adsorptionprocess was jointly controlled by particle diffusion and film diffusion; theadsorption process was endothermic and spontaneous, and predominatedby the physical and chemical adsorption according to the thermodynamicparameters results.（4） Electrostatic attraction and hydrogen bonding might be the twomain forces for the adsorption of MB, although both of n-Ï€ conjugate andvan der Waals forces also contributed to them.