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영어

The isothermal adsorption and kinetics of phosphorus in aqueous solutions of oyster shell powders calcined at a specific temperature were addressed in this study. Raw oyster shell powder was identified to have a Ca content of 64.3 wt.% and a thermal weight loss of 45.9%. The physicochemical properties of the raw oyster shell powder and oyster shell powder calcined at 550oC, 750oC, and 900oC respectively were investigated in advance. In the phosphorus adsorption experiment, adsorption equilibrium was achieved within 1 minute with a rapid pH increase in all experimental cases, suggesting that activated calcium oxide constituting the oyster shell powder caused rapid hydration in aqueous solution. The higher the initial phosphorus concentration in the aqueous solution, the higher the phosphorus adsorption of oyster shell powder due to the influence of the phosphate ion concentration gradient. Additionally, the higher the calcinating temperature, the higher the phosphorus adsorption due to the difference in decarboxylation of oyster shells. The isothermal adsorption data fitted well with the Fruendlich model, with adsorption constants (KF) of 0.0330~10.3110 (mg/L1/n)/(g/L1/n), heterogeneity factor (n) of 0.5439~1.1060, and R2 of 0.7759~0.9956. The pseudo-second-order kinetic model described the experimental data well, and the amount of phosphorus adsorbed at equilibrium (qe) was 3.0460~40.4858mg/g. In conclusion, the experimental results suggested that high phosphorus removal efficiency could be obtained because adsorption was more spontaneous and cooperative when oyster shells were calcined above the critical temperature for decarboxylation. Comparative result for the adsorption capacity of several alternative adsorbents emphasized that thermally activated oyster shells were effective for phosphorus removal from water systems.