The Preparation And Application Of Silica-based Mesoporous Materials And Modified Sugarcane Bagasse In Phosphate Adsorption

Phosphorus is one of critical nutrients for biological and chemical processes in natural water bodies. The excess of phosphate has been recognized as the main factor for eutrophication and algae bloom in surface waters, especially in slow-moving rivers and lakes. Phosphate is usually released into aqueous systems from detergent, pigment formulation, water treatment, electronic industry, mineral processing, and the overapplication of fertilizers. Eutrophication caused by high levels of phosphate leads to the over-production and accumulation of micro and macro organisms, which can deteriorate the water quality of receiving water bodies and induce aesthetic problems. Recently, various techniques have been used for phosphate removal, including physicochemical and biological methods. For example, chemical precipitation with lime, alum and iron salts or enhanced biological treatment and some physical methods including crystallization, electrodialysis, reverse osmosis, ion exchange and adsorption have been used for the removal of phosphate. Among these methods, adsorption has become comparatively more effective and economic method for phosphate removal. Additionally, this method can be used for the collecting and recycling phosphate, which can save the exhausted phosphate resource.In this stuty, series of lanthanum doped mesoporous MCM-41 were prepared by two different methods, and modified sugarcane bagasse by chemically modified were preparated. The surface structure of the materials was investigated with X-ray diffraction, N2 adsoropion/desoprotion technique, elemental analysis, zeta potential analysis, surface area determination and SEM. The effects of different Si/La molar ratio, the amount of lanthanum-doped adsorbent, at different contact time, initial concentration of phosphorus solution and pH, the effect of interfering ions was also investigated.The result of researches show that:(1) Based on XRD, N2 adsorption/desorption, the structure of Lanthanum doped MCM-41 materials kept well; (2) Phosphate removal from aqueous solutions was investigated by lanthanum doped mesoporous MCM-41, the phosphate adsorption capacities increase with the increasing amount of La incorporation. The lanthanum doped MCM-41 materials by hydrothermal and sol-gel mehthod for phosphate removal, the adsorption capacity were 19.77 and 21.1 mg/g, respectively. When the adsorbent dosage is 0.400g, the efficiency of 50mg/L phosphate removal is more than 99%. However, foreign ions decreased the phosphate adsorption capacity. (3) The lanthanum doped MCM-41 materials by hydrothermal and sol-gel mehthod for phosphate removal, the max adsorption was achieved with pH in a range of 2-3 and 4-8, respectively. (4) The modified sugarcane bagasse was used to remove the phosphate from aqueous solutions by adsorption. The adsorption capacity of the modified sugarcane bagasse was 21.3 mg/g at natural pH when 50mg/L of phosphate solution was adsorbed by 0.100g sorbent. The desorption study indicated that the sorbent could be recovered under 0.05M NaOH solution within 30 min. (5) In the studies of this three modified materials were used to remove the phosphate from aqueous solutions by adsorption, the kinetic data was fitted using the pseudo-first-order equation and the pseudo-second-order equation. Among the kinetic model studies, the pseudo-second-order equation was the best fit model for describing the adsorption process. Equilibrium data were modeled using the Langmuir and the Freundlich isotherm.