Preparation Of Phosphorus Removal Adsorbent With Chitosan As Carrier And Its Properties P-containing Wastewater

Phosphorus,as an important industrial and agricultural raw material,is mainly derived from rich-phosphate rocks.However,phosphate rock as a non-renewable resource,it's reserves have declined sharply with large amounts of mining,while a large amount of phosphorus is discharged into natural water bodies due to people's activities of production and life,resulting in eutrophication of natural water bodies,which endangers the ecological environment of the water body and human health.Therefore,the removal and recovery of phosphorus in wastewater is of great significance for sustainable development.As an effective phosphate removal method,the adsorption method has the advantages of simple equipment,convenient operation,and renewable adsorbent.The key point of the adsorption method is to prepare an adsorbent with excellent performances.Chitosan,as a natural polymer material that is easily biodegradable,biocompatible and can be prepared in large quantities,is widely used in the preparation of adsorbents to remove metal cations,harmful anions and dyes.In this paper,two kinds of phosphorus removal sorbents were prepared with carrier of chitosan.The performances of the sorbents were investigated in detail,and the resource recovery of adsorbed phosphate was rudimentary explored.In order to effectively remove phosphate in wastewater and convert it into useful materials,the chitosan granules loaded ?-AlOOH(?-AlOOH@CS)were prepared by a hydrothermal method,and a novel strategy was proposed to treat the used adsorbent.The size of the freeze-drought particle adsorbent was in the range of 2 to 3 mm with the porous network structure.The maximum adsorption capacity of the adsorbent is 45.82 mg/g,which is higher than most of the previous reported adsorption capacities of adsorbents with aluminum basis.The adsorption was a spontaneous,endothermic,multi-layered,non-uniform adsorption.The adsorption rate is fast,and the adsorption capacities reached a half of the equilibrium adsorption capacities in 0.5 h.The common coexisting anions have little effect on the adsorption.When the initial pH of the solution was in the range of 4 to 6,the adsorption capacity remained basically unchanged.The adsorbent was used to treat the waste water which simulated discharged from MBR method.The results showed that the influent rate had a great effect on the treatment effect,and the treatment amounts to achieve the standard discharge were 8.4 L and 13.3 L at influent rate of 3.0 mL/min and 1.5 mL/min,respectively.After adsorption,the chitosan was separated by alkali dissolution from adsorbent,which can be used as a reliable raw material for preparing the adsorbent.The pH is adjusted by adding phosphoric acid into the NaOH solution.After adding phosphate acid to adjust the pH of the NaOH solution,the aluminum in the solution was recovered as aluminum phosphate by hydrothermal reaction and calcination,while the P-rich solution can be used as industrial raw materials or liquid fertilizers.The ?-AlOOH@CS shown excellent dephosphorization performance,while the resource recovery of adsorbed phosphorus and the effective reuse of adsorbents were realized.In order to improve the acid resistance,phosphorus removal and separation performance of the chitosan hydrogel adsorbent,the magnetic microspheres loaded La(OH)3 with interpenetration hydrogel network of chitosan and polyvinyl alcohol(La(OH)3@MIPN)were prepared by emulsion cross-linking.The particle size range of the microspheres is 2.66-32.36 ?m,it performs great swelling performance,the particle size becomes 1.26 times the original within 30 min in solution.In the aqueous solution of pH>5,the dissolutions of metal ions and organics are slight,demonstrating a good stability of La(OH)3@MIPN in weak acid,neutral and basic environment.The saturation magnetization value of the microspheres is 11.6 emu/g,and the microspheres exhibited superparamagnetic nature,showing outstanding magnetic separation characteristics.The adsorbent showed a fast adsorption rate,and reached the adsorption equilibrium with in 1 hour.The adsorption process conformed to the pseudo-second-order kinetic model.The maximum adsorption capacity was 44.59 mg/g,which was 7.6 times of the adsorption capacity of magnetic microspheres without La(OH)3 coated with interpenetration hydrogel network of chitosan and polyvinyl alcohol(MIPN),indicating that adsorption capacity was dramatically improved.The adsorption mechanism is mainly ion exchange between phosphate and hydroxyl group.The adsorption capacities are hardly affected by coexisting ions and has a strong selectivity.The initial pH of the solution is a significant effect on adsorption,and adsorption capacities were higher under acidic and neutral solutions.The adsorbed adsorbent can be effectively regenerated using NaOH solution.After 5 times adsorption-desorption cycles,the adsorption capacity can still maintain 89.9%of the initial adsorption capacity,showing the good regeneration property of the La(OH)3@MIPN.