Abstract: Heavy metal pollution in water is a serious threat to human health. A series of strategies are being adopted in many countries for the removal of metal pollution from water. In the present study, the bio-adsorption of Cr (Ⅵ) by apple pomace was systematically studied. The adsorption rate of Cr (Ⅵ) by apple pomace was increased with decreasing particle size of apple pomace, but positively dependent on apple pomace dosage at the same initial Cr concentration, and showed a general increasing trend with increasing initial Cr concentration at the same apple pomace dosage. The decreasing order of the effects of three operating parameters on Cr (Ⅵ) adsorption was temperature ＞ pH ＞ adsorption time, and the optimal adsorption conditions were pH 4, 60 ℃ and 5 h as determined using an orthogonal array design. Under these conditions, the adsorption rate of Cr was 72.43%. Cr (Ⅵ) adsorption by apple pomace was a 120 min fast adsorption process followed by a slow adsorption process, could be described well with Freundlich adsorption equation, and obeyed second-order kinetics. The optimal solid/liquid ratio for adsorbing Cr (Ⅵ)  in 50 mg/L aqueous solution with apple pomace was 8:1000 (m/V). In addition, apple pomace was more effective in adsorbing Cr (Ⅵ) at low and middle concentrations (≤ 30 mg/L) than activated carbon.

Key words: apple pomace, Cr6+, bioabsorption, adsorption isotherm, dynamic adsorption curve, solid/liquid ratio