| Phosphate is an important factor for the occurrence of surface water eutrophication,and is also a non-renewable resource which faces a potential depletion crisis.At present,the chemical de-phosphate technology used in most municipal wastewater treatment plants leads to the migration of most part of phosphate into sludge,then the sludge volume increases,the phosphate forms in sludge is difficult to be recycled,the waste of phosphate resource occurs.Moreover,the tail water from the WWTP even contains phosphate with low concentration,which still causes eutrophication when it enters the surface water body.Thus,it is of great significance to develop the adsorption approach for high efficient recovery of phosphate with low concentration in wastewater.In this study,La?OH?3 loaded magnetic cationic hydrogel composites MCH-La?OH?3-EW was used to absorb low strength phosphate in water or wastewater.The adsorption performance and mechanism of MCH-La?OH?3-EW,as well as the scale-up preparation technology were studied,furthermore,the performance of this scale-up prepared MCH-La?OH?3-EW was evaluated.The adsorption process of MCH-La?OH?3-EW toward low strength indicated that its maximum adsorption capacity was 98.34±7.39 mg/g at the initial phosphate concentration of 2–5 mg/L and the equilibrium time of 2–4 h.The adsorption process belonged to spontaneous endothermic reaction.The adsorption capacity of MCH-La?OH?3-EW towards phosphate could maintain relatively stable within p H of 4–10,and be less affected by co-exist ions.After 10 cycles of adsorption-desorption-recycle,the adsorption capacity of regenerated MCH-La?OH?3-EW still remained 63.4–75.27%of its maximum value.The adsorption mechanism analysis showed that both quaternary amine groups and La?OH?3 of MCH-La?OH?3-EW were involved in the process of phosphate adsorption.The electrostatic adsorption mainly occurred in the initial stage of adsorption and then the adsorption was is gradually replaced by complexation between phosphate and hydroxyl of La?OH?3.As the results,the La-P complexation was the final form of adsorption and the electrostatic adsorption sites were not reached saturation status.The scale-up preparation process of MCH-La?OH?3-EW was studied,a 125-fold mass?280 g?adsorbent was successfully prepared,and the process conditions of scale-up preparation were determined.It is verified that MCH-La?OH?3-EW of scale-up preparation can replace chemical de-phosphate technology for the treatment of low concentration phosphate in secondary wastewater effluents and surface water.The capacities of phosphate adsorption were 48.86 mg/g and 41.09 mg/g respectively,and the removal rate reached 97.71%and 97.34%.The cost of MCH-La?OH?3-EW prepared was about 1874.82 yuan/kg,the treatment cost of wastewater containing low concentration phosphate with 40 recycles of absorbents was about 5.08 yuan/ton,reducing regeneration cost and adopting industrial material could further improve the economy of adsorbent.Therefore,MCH-La?OH?3-EW had good feasibility and application prospect in the treatment of wastewater containing low concentration phosphate. |
PDF Full Text Request