ADSORPTION OF CD(II) IONS USING NATURAL ZEOLITE WITH DEALUMINATION AND DESILICATION TREATMENT

• Main Author: Dawati, Celine
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/73234
• Institution: Institut Teknologi Bandung

Heavy metals are one of the environmental pollutants that must be considered by every country in the world. Cadmium is an example of a heavy metal that can pollute the environment, especially water pollution. According to the World Health Organization (WHO), the maximum level of cadmium ions allowed in drinking water is 0,003 mg/L. In this study, Cd(II) ions were adsorbed using natural zeolite from Lampung, Indonesia. There are four types of zeolite that will be used, namely untreated natural zeolite, dealuminated zeolite, dealuminated-desilicated zeolite, and desilicated zeolite. Natural zeolite was treated with dealumination and desilication with the aim of increasing the surface area of the zeolite so that the adsorption process was expected to occur better. FTIR characterization using the ATR method has been carried out. The results show that at wave numbers around 520-535 cm–1 and 783-794 cm–1, there is a stretching vibration of the Si- O/Al-O bond and an asymmetric stretching vibration of the T-O-T bond (T = Si or Al) around 1031-1051 cm–1. The peak shift occurred in the T-O-T absorption area for the treated zeolite so that the dealumination and desilication processes were successful. The results of the XRD characterization showed that the main type of Lampung natural zeolite was clinoptilolite (HEU) and the degree of crystallinity was 64,311%. The degree of crystallinity of dealuminated zeolite, dealuminated-desilicated zeolite, and desilicated zeolite was 68,012%; 74,805%; and 69,113% respectively, so they can be concluded that the dealumination and desilication treatments did not damage the zeolite structure. The optimum adsorption conditions were at pH 6 and a contact time of 20 minutes for 10 mL of 200 ppm Cd(II) solution. Kinetic studies showed that the adsorption process following a pseudo-second-order model with a rate constant of 0,432 g.mg–1.minute–1 for untreated zeolite; 0,273 g.mg–1.minute–1 for dealuminated zeolite; 0,036 g.mg–1.minute–1 for dealuminated-desilicate zeolite; and 0,056 g.mg–1.minute–1 for desilicated zeolite. The value of the zeolite rate constant after treatment decreased because the diffusion path was longer so the diffusion process of Cd(II) ions was slower. The long diffusion path is due to the formation of larger zeolite pores. The adsorption process of Cd(II) ions using the four zeolites followed the SIPS isotherm model with maximum adsorption capacity (qm) of untreated zeolite, dealuminated zeolite, dealuminated-desilicated zeolite, and desilicated zeolite of 15,178 mg/g; 17,869 mg/g; 37,071 mg/g; and 44,945 mg/g respectively. The qm value of zeolite after treatment has increased compared to zeolite without treatment, especially desilicated zeolite. This result shows that desilication is more effective than dealumination in increasing the adsorption capacity of zeolite. The adsorption process is an endothermic reaction, the reaction takes place spontaneously, and the entropy is positive (which has randomness). SEM-EDS characterization showed differences in the morphology of untreated natural zeolite, dealuminated zeolite, dealuminated-desilicated zeolite, and desilicated zeolite with a Si/Al ratio of 3,940; 4,570; 3,802; and 3,371 respectively. The Cd %weight value indicated the order of the adsorption ability of the four zeolites starting from the best: desilicated zeolite, dealuminated-desilicated zeolite, dealuminated zeolite, and untreated natural zeolite.