Study On Phosphorus Adsorption From Water By Lanthanum Hydroxide Embedded Interpenetrating Network Poly (Vinyl Hydrogel Beads

For the fact that water eutrophication is serious and phosphorus resources are gradually depleted,the conventional biological with chemical precipitation treatment can only reduce the concentration of phosphorus in the water,but not realize the recycling of phosphorus resources,and will cause secondary pollution.Sorption is widely used in the field of environmental treatment because of its advantages of high efficiency,simple operation,low cost,easy separation and reuse.However,the traditional sorbents have problems such as low sorption capacity,slow sorption rate,and poor reusability.And new types of phosphorus removal sorbents are needed.Highly hydrophilic hydrogel with three-dimensional network structure which can be introduced with target group through functional design to increase sorption sites is a kind of good phosphorus removal sorbent.In this paper,a novel polyvinyl alcohol-sodium alginate-lanthanum hydroxide?PVA-SA-LH?hydrogel microsphere sorbent with high phosphorus sorption capacity,easy separation,and good recyclability was synthesized by introducing lanthanum hydroxide with high affinity to phosphorus into polyvinyl alcohol-alginate hydrogel.The static sorption performance and sorption mechanism of phosphate were investigated.And the dynamic penetration curves and its treatment effect on actual wastewater were studied under different conditions.The main conclusions obtained are as follows:?1?PVA-SA-LH and PVA-SA hydrogels have been successfully synthesized.The characterization results indicated that PVA-SA-LH hydrogel had a selective adsorption capacity for phosphorus and formed strong chemical bonds with it.?2?The maximum sorption capacity of both hydrogels was achieved at pH=3.The sorption capacity of PVA-SA hydrogel was 13.40 mg/g,and that of PVA-SA-LH hydrogel was 31.65 mg/g;With the increase of sorbent dosage,the sorption capacity of PVA-SA-LH hydrogel gradually decreased while the sorption capacity of PVA-SA hydrogel remained stable and then decreased slightly.The competitive adsorption of coexisting anions on PVA-SA gels was stronger than that of PVA-SA-LH gels.After five adsorption-desorption cycles of PVA-SA-LH hydrogels,the adsorption capacity remained above 80%of the initial adsorption capacity.These all indicated PVA-SA-LH hydrogel had great selective sorption and recovery ability to phosphorus.?3?The sorption kinetics curve of PVA-SA-LH hydrogel conformed to the pseudo-second-order kinetics model,which indicated that the adsorption was mainly chemical sorption.The sorption of PVA-SA hydrogel at low concentration accorded with pseudo-first-order kinetics model,mainly with physical sorption.At 25mg/L it was in line with pseudo-second-order kinetics model.Intra-particle diffusion model results showed that the sorption rates of both hydrogels were mainly limited by the diffusion process of phosphate within the hydrogels,indicating increased porosity was beneficial to increase adsorption capacity.The two hydrogel sorption isotherms conformed to the Langmuir model.And the maximum sorption capacity was 45.17 mg/L and 16.04 mg/L,respectively.The addition of LH did not chang the homogeneous adsorption process of the single layer.The sorption mechanism of PVA-SA-LH hydrogel to phosphate mainly was electrostatic attraction and ion exchange under acidic conditions,and was dominated by Lewis acid base under alkaline conditions because the electrostatic repulsion between La-O^-and HPO₄^2-was not conducive to the ion exchange.?4?The dynamic adsorption capacity of phosphorus on the PVA-SA-LH hydrogel increased with the increase of the filling quality and the influent phosphorus concentration,and decreased with the increase of the influent water flow rate.In the three models,Thomas model best simulated the wastewater breakthrough curves.?5?The treatment quality of PVA-SA-LH hydrogel on low-concentration real-life sewage could reach the national A-level standard.The penetration curve parameters and Thomas model simulation results showed that the influence of organic substances and various ions in the actual wastewater on the adsorption process of the gel was small.The hydrogel had a strong selective adsorption capacity for phosphorus.