Effective Cu(II) ions adsorption from aqueous solutions using low grade oolitic hematite tailing with phosphorus: response surface methodology

In this work, low grade oolitic hematite tailing with phosphorus (LGOHTWP), an industrial solid waste was adopted as adsorbent to remove Cu(II) ion from aqueous solution. Influences of experimental factors including initial pH, initial Cu(II) concentration and LGOHTWP dosage on the Cu(II) ion removal were analyzed, and the related adsorption mechanism was discussed. Aiding by Box-Behnken design based response surface methodology, an empirical quadratic equation expressing the relationship between the Cu(II) removal efficiency and adsorption parameters including initial pH, adsorbent dosage and initial Cu(II) ion concentration was obtained. In addition, the optimum conditions (initial Cu(II) concentration = 21.60 mg/L, adsorbent dosage = 79.23 g/L, initial pH = 5.71) were obtained by plotting 3-D response surfaces from the mathematical model. On the optimum conditions, the experimental Cu(II) ion removal efficiency reached 99.98%, which was in accordance with the predicted value. The results indicate that the adsorption of Cu(II) ion onto LGOHTWP is strongly dependent on pH value of the solution. Adsorption kinetics accords with the pseudo-second-order model, and the equilibrium adsorption data fits well with Langmuir isothermal model. The maximum capacity of adsorption is 26.95 mg/g at 50 degrees C. Thermodynamic study reveals that adsorption of Cu(II) ion onto LGOHTWP is spontaneous and endothermic. In general, LGOHTWP is an efficient and promising adsorbent for Cu(II) ion removal from wastewater.