Utilizing modified clinoptilolite for the adsorption of heavy metal ions in acid mine drainage

Abstract

The modified clinoptilolite was used to mitigate Cu(II) and Zn(II) in acid mine drainage. This study explored integrating the cationic surfactant HDTMA-Br and the cation Mg(II) into clinoptilolite. The added HDTMA-Br concentration is designed to give a value with constant cation exchange capacity (k×CEC). The modified clinoptilolite using Mg(II) ions gives a higher volume and pore diameter of modified zeolite than natural clinoptilolite. However, the addition of HDTMA-Br can cover the surface of natural clinoptilolite, causing a decrease in pore volume and diameter and the adsorbent surface area. The addition of HDTMA-Br at level 1 of CEC (HDCL-1) led to an increase in the adsorption capacity of zeolite towards Cu(II) and Zn(II). According to the Langmuir model, the modified zeolite HDCL-1 exhibited the highest adsorption capacity, reaching 15.16 mg/g for Cu(II) and 15.51 mg/g for Zn(II). The findings suggest that Cu(II) and Zn(II) adsorption may involve an ion exchange mechanism. The use of HDCL-1 as an adsorbent at an initial pH of 5 can remove Cu(II) and Zn(II) ions by 100% and 75.5%, respectively in AMD model solutions that contain a ratio of Cu(II):Zn(II) = 1:1. HDCL-1 composite selectivity is better at absorbing Cu(II) metal ions than in absorbing Zn(II) ions. Continuous adsorption is carried out in a fixed bed adsorber column with a diameter of 1.25 cm. The concentration of Cu(II) coming out of the fixed bed column follows Thomas's model, and it is obtained that there is an increase in HDCL-1 saturation time from 0.2 h to 20.5 h if the adsorbent height is increased from 2 cm to 2.5 cm.

Keywords

• Cu(II)
• Zn(II)
• Adsorption
• Surfactant
• Modified clinoptilolite