ADSORPTION OF METAL Zn AND Cd FROM AQUEOUS SOLUTION BY CARBOXYMETHYL GLUCOMANNAN

• Main Author: Resdiana, Renta
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/38209
• Institution: Institut Teknologi Bandung

Most of the heavy metals released into the environment by various industrial activities and become one of the serious problems for the environment. Wastewater from various industries such as metal plating, fertilizers, pesticides, paints industries, and batteries in general contain some heavy metals such as Pb, Cd, Cu, Zn, and Hg. Unlike organic wastes, heavy metals cannot be degraded in nature, has a high toxicity, and can accumulate in living organisms. Metal zinc (Zn) and cadmium (Cd) is a heavy metal commonly found in industrial wastes. Several methods have been developed for treating wastewater containing heavy metals such as coagulation, membrane filtration, ion exchange, and adsorption. Among all the treatments proposed, adsorption using natural polymer adsorbents is one of the most popular methods. Glucomannan is one of the potential natural polymer adsorbent as metal biosorption. Glucomannan is a polysaccharide which has composed of ?-1,4-linked D-glucose and D-mannose monomers. In addition to being a source of food, glucomannan can be used as an adsorbent of toxic compounds and metal ions. In this study, carboxymethyl glucomannan obtained from the reaction of isolation from low viscosity (ILG) and high viscosity glucomannan (IHG) with monochloroacetic acid using NaOH catalyst at pH 9-10 with stirring for 3 hours and a temperature of 60?C. Carboxymethyl glucomannan precipitated using HCl, then washed to neutral with 90% ethanol, and dried in an oven at a temperature of 60?C. Carboxymethyl glucomannan obtained from IHG (KMIHG) and ILG (KMILG). Carboxymethyl glucomannan structure characterized by FTIR, obtained -COONa form is the most dominant contained in the wave number for KMILG and KMIHG of 1633 cm-1 and 1629 cm-1. The degree of substitution (DS) was determined using the back titration method, the DS value obtained for ILG (DS = 0.297), IHG (DS = 0.134), KMILG (DS = 0.489), and KMIHG (DS = 0.412). The effect of pH, time, initial concentration of metal, and adsorption-desorption was investigated. The result showed that adsorption capacity rapidly reached equilibrium within 60 minutes and the optimum pH for adsorption was 6. Adsorption capacity increased with the increasing DS of carboxymethyl group (KMILG > KMIHG > ILG > IHG). Among the tested metals, the order of the adsorption capacity is Cd(II) greater than Zn(II) in mass basis, with adsorption capacity ILG for Zn(II) 12.08 mg/g and Cd(II) 14.50 mg/g; IHG for Zn(II) 11.06 mg/g and Cd(II) 13.76 mg/g; KMILG for Zn(II) 13.61 mg/g and Cd(II) 17.70 mg/g; and KMIHG for Zn(II) 13.04 mg/g and Cd(II) 15.90 mg/g. Adsorption isotherms obtained for the adsorption of metal of the entire adsorbents sample followed the Langmuir adsorption isotherm with R2 is close to 1. The use of adsorbent three times repetition shows percent desorption results for the entire sample of not less than 85% for glucomannan and more than 90% of carboxymethyl glucomannan. Despite the decrease in the adsorption capacity of the metal ions Zn(II) and Cd(II), the entire adsorbent glucomannan and carboxymethyl glucomannan can be used repeatedly without significantly changing the adsorption capacity.