Preparation Of FeOOH/γ-Al₂O₃ Composites And Their Adsorption And Removal Of Phosphorus From Water

Phosphorus is an important part of the food chain and agricultural economy,and approximately 50%of the phosphorus fertiliser applied during agricultural production is lost to rivers and lakes leading to eutrophication,which in turn is harmful to human health and the ecological environment.Addressing eutrophication has been a huge challenge in the environmental field.At present,the key to limit its large-scale application is how to make the adsorbent the highest possible adsorption capacity and maintain stable adsorption performance after multiple regenerations.Among many common adsorbents,iron（hydrogen）oxide and aluminum（hydrogen）oxide nanoparticles show great potential due to their inexpensive,easy availability,high adsorption capacity for phosphorus,and environmental friendliness.but both have the problem of how to further increase the adsorption capacity and address the difficulties in regenerating the adsorbent.Based on the laboratory research basis,crystalline and amorphous FeOOH were prepared and their adsorption of phosphorus in water was investigated.The adsorption capacity of amorphous FeOOH for phosphorus was much higher than that of crystalline FeOOH;on this basis,using FeCl₃·6H₂O as the iron source,and the preparedγ-Al₂O₃ with large specific surface area and pore size（specific surface area and pore volume of 493.7 m²/g and 3.62 cm³/g）as the template.The FeOOH/γ-Al₂O₃ composites were obtained by growing amorphous FeOOH with smaller particles once in the restricted domain within the alumina pore channel.Its adsorption performance and regeneration performance were investigated in detail.The FeOOH/γ-Al₂O₃ composite prepared by impregnation showed an efficient adsorption of phosphorus with an adsorption capacity of 82.47 mg/g,which is higher than the adsorbent materials reported in the literature.The adsorption process conforms to the pseudo-second-order kinetics and Langmuir isothermal adsorption model,and the monolayer saturation adsorption capacity of the adsorbent was 127.23 mg/g at 25°C.Adjusting the pH of the phosphorus solution,the maximum adsorption capacity was 86.36 mg/g at pH=6,and the adsorption capacity was greater than 79 mg/g in all phosphorus solutions of pH=3-10.The FeOOH/γ-Al₂O₃ composite were regenerated by the hydrochloric acid-impregnation method.The composite material dissolved the hydroxy iron oxide for phosphorus adsorption during the regeneration process,while the alumina was basically undissolved,and then the hydroxy iron oxide was produced again in the restricted domain of the alumina pore channel,thus achieving the regeneration of the adsorbent.The results of the regeneration study showed that the adsorption capacity still maintained at 71.67 mg/g and the regeneration rates were all greater than 85%after three regenerations,which means it had excellent regeneration effect.In conclusion,the FeOOH/γ-Al₂O₃ composite adsorbent has practical application value due to its simple preparation process,fast adsorption rate,high adsorption capacity and good regeneration adsorption performance.