DEVELOPMENT OF ADSORBENT FROM MONTMORILLONITE FOR REMOVAL FE (III) AND MN (II) FROM THE MODEL OF ACID MINE WATER

• Main Author: Jamal, Rizqan
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/49552
• Institution: Institut Teknologi Bandung

Mining sector is still one of biggest non-tax state revenue for Indonesia, it is necessary to minimize the negative outcome which generate by mining activities. Acid mine drainage (AMD) is one of the major wastes sourced from mining activities that has low pH and high concentration of iron and manganese. Adsorption is the inexpensive and easy methods that can be used to remove heavy metals from a solution. Montmorillonite is one type of adsorbent originated from clay mineral that is widely available in Indonesia. Montmorillonite will be modified by homogenizing the exchangeable cation and adding other compounds to increase the number of active sites. This modification aims to increase the adsorption ability of montmorillonite to adsorb Fe (III) and Mn (II) ions. Montmorillonite is obtained from bentonite; it is necessary to purify montmorillonite with sedimentation method. Furthermore, the metal content of montmorillonite was modified by adding sodium ions to obtain Na-montmorillonite and calcium ions to obtain Ca-montmorillonite. To find out the amount of modifying compounds that needed, the value of cation exchange capacity (CEC) analyzed with methylene blue method. After the CEC value was obtained next step is modification of montmorillonite. Modifications were made by addition of benzalkonium chloride to form organoclay, variation made by addition certain amount of surfactant based on CEC. The variations are montmorillonite treated with 1 x CEC, 2 x CEC, and 3 x CEC. These modifications produced two types of homoionics montmorillonite and six types organoclays. Adsorbents are characterized using the Brunauer-Emmet-Teller (BET) method. The study of the effect of time on adsorption, the effect of initial concentration of ions on adsorption, and the effect temperature on adsorption were done to justify the most effective adsorbent. The concentration of Fe (III) and Mn (II) ions in AMD model before and after adsorption were determined by using atomic absorption spectroscopy. The study of the effect of time on adsorption of Fe (III) and Mn (II) using eight adsorbents showed that the percentage values of removal of Fe (III) and Mn (II) were fluctuated and no equilibrium point was obtained. The process starts to stabilize at 30 minutes, for the next test 30 minutes is used as the adsorption time. Based on the percentage value of removal of Fe (III), the order of effectiveness of the adsorbent is obtained as follows: Na- Montmorillonite > Ca-Montmorillonite > Organo-Na-Montmorillonite 3 CEC > Organo-Ca-Montmorillonite 3 CEC > Organo-Na-Montmorillonite 2 CEC > Organo-Ca-Montmorillonite 2 CEC > Organo-Na-Montmorillonite 1 CEC > Organo-Ca-Montmorillonite 1 CEC, the higest percent removal was 99.78% from initial concentration 10 mg/L using 1% m/v adsorbent. While based on the percentage value of removal of Mn (II), the order of effectiveness of the adsorbent is obtained as follows: Na-Montmorillonite (II) ions is as follows, Na-Montmorillonite > Ca-Montmorillonite > Organo-Na-Montmorillonite 3 CEC > Organo-Ca-Montmorillonite 3 CEC > Organo-Ca-Montmorillonite 1 CEC > Organo-Ca-Montmorillonite 2 CEC > Organo-Na-Montmorillonite 1 CEC > Organo-Na-Montmorillonite 2 CEC, the higest percent removal was 99.07% from initial concentration 10 mg/L using 1% m/v adsorbent. The initial concentration of Fe (III) ions increased from 100 ppm to 8000 ppm, and the initial concentration of Mn (II) ions from 50 ppm to 500 ppm. The results of the study of the influence of initial concentrations of Fe (III) and Mn (II) showed the percentage of removal decreased with the increasing of initial concentrations of Fe (III) and Mn (II) after adsorption with Na-Montmorillonite and Ca-Montmorillonite. The effect of temperature on adsorption of Fe (III) and Mn (II) by Na-Montmorillonite and Ca-Montmorillonite shows that the adsorption process was an endothermic reaction in which percent removal of Fe (III) and Mn (II) increases as the temperature process were increased from room temperature to 45oC. The adsorption and desorption process took place simultaneously as H2SO4 in AMD model was a leaching agent, capable of desorbing Fe(III) and Mn (II) ions from adsorbent. Simultaneous adsorption and desorption processes cause the percentage value of removal of Fe (III) and Mn (II) to fluctuate in the study of effect of time on adsorption so that the equilibrium point cannot be determined and the value of the adsorption capacity, adsorption isotherm, adsorption kinetics, and adsorption thermodynamics cannot be determined. For study purposed, the maximum adsorption capacity is determined. The use of Na-Montmorillonite adsorbents shows the largest maximum adsorption capacity value, 1.04 mg/g, from the initial Fe (III) and Mn (II) ion concentrations of 10 mg / L using 1% m / v adsorbent. The maximum adsorption capacity increased with increasing initial concentrations of Fe (III) and Mn (II) ions and increased as the process temperature increases. Characterization by the BET method gave the data as follows, the specific surface area of Montmorillonite increased from 34.36 m2/g, to 59.13 m2/g in Ca-Montmorillonite, and 63.37 m2/g in Na-Montmorillonite. The pore volume of Montmorillonite increased from 0.11 cm3/g, to 0.17 cm3/g in Ca-Montmorillonite, and 0.16 cm3/g in Na-Montmorillonite. The pore diameter Montmorillonite decreased from 4.16 nm, to 3.61 nm in Ca-Montmorillonite, and 3,10 nm in Na-Montmorillonite. It can be concluded that Na-Montmorillonite is an effective and inexpensive adsorbent for the removal of Fe (III) and Mn (II) from AMD model.