Clean Water and Sanitation (SDG 6), Climate Action (SDG 13)
Removal Efficiency of Pb 2+ and Cd 2+ Ions from Wastewater by Using Unmodified and Modified Jack Wood Sawdust
Udaya Kumara Jayasundara Institute of Chemistry Ceylon, Sri Lanka
Discharge of heavy metals into water bodies from various industries has become a serious global problem. Those heavy metals may exist in different oxidation states could form complexes with ligands in aqueous media and tend to bioaccumulate in the food chains causing acute or chronic diseases. Therefore, efficient, and cost-effective methods to remove them from water are very important. Though there are different methods available, adsorption has become the most versatile procedure to remove pollutants from water. In this study, the use of jack wood saw dust (JWSD) was tested as a prospective adsorbent to remove Pb 2+ and Cd 2+ ions from wastewater. The JWSD was collected from local carpentry shops, sieved to obtain uniform material, cleaned with deionized water and dried to constant mass prior to the preparation of adsorbent. The study was carried out with unmodified JWSD, acid modified JCWD and base modified JCWD. Cleaned and dried unmodified JWSD was treated with HCl or NaOH, shaken for four hours, washed, and dried to yield acid or base modified JWSD. Batch experiments were carried out to determine the factors affecting adsorption process. The adsorption study was conducted by varying the initial metal ion concentration, adsorbent dosage, time, temperature, and pH. It was discovered that the unmodified JWSD had a point of zero charge of 7.3. The results of unmodified JWSD showed that the equilibrium adsorption capacities of Pb 2+ and Cd 2+ were 1.500 mg/g and 0.110 mg/g, respectively. The acid modified JWSD with 5 M and 0.25 M HCl showed the highest adsorption capacities of 2.660 mg/g for Pb 2+ adsorption and 0.250 mg/g for Cd 2+ adsorption which demonstrated about 2fold increase compared to unmodified JWSD. The base modified JWSD with 0.25 M HCl showed the highest adsorption capacities of 4.047 mg/g for Pb 2+ adsorption and 0.250 mg/g for Cd 2+ adsorption which demonstrated approximately 3-fold increase compared to unmodified JWSD. From the results, it was revealed that both acid and base modified JWSD are having higher adsorption capacities as well as higher percentage removals compared to unmodified JWSD. Further, it can be concluded that the base modified JWSD yielded better results compared to acid modified JWSD. However, the activated charcoal (AC) demonstrated lower removal efficiencies compared to modified JWSD and hence it can be considered as an alternative to AC, which is better both in terms of cost and performance for the removal of Pb 2+ and Cd 2+ from aqueous media. The equilibrium studies demonstrated that the Langmuir adsorption isotherm obeys with the removal of both Pb 2+ and Cd 2+ . In addition, adsorption of both ions obeyed the Pseudo Second Order (PSO) kinetics and the thermodynamic data revealed that the adsorption process to be exothermic. Both modified and unmodified JWSD before and after adsorption were characterized using Fourier Transformation Infra-red (FTIR) spectroscopy and scanning electron microscopy (SEM).
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