Removal of lead from aqueous solution by green synthesis of adsorbents using Sapodilla leaves extract

Abstract

Rapid development of population, industrialization, and urbanization leads to global contaminants of water pollution by heavy metal ions that cause threat to the health of human and other living creatures. Out of all heavy metal pollutants, lead should be taken into consideration due to it detrimental effects. Among all available treatment methods for this issue, adsorption has been found to be better in terms of simplicity of design, cost effective, ease of operation, and environmentally friendly. Currently, activated carbon is one of the most used and popular commercial adsorbent for treating of heavy metal from aquatic medium. However, its application is limited due to relatively high commercial cost. The use of low cost biomass waste to produce adsorbents has been shown to provide economical solution to this problem. This study aims to develop waste based adsorbents using sapodilla (Manilkara Zapota) leaves extract along with Fe salt as coating materials for alumina beads (Fe/C/Al2O3), commercial molecular sieve (Fe/C/M.S), and cockle shell (Anadara Granosa) (Fe/C/C.S). All of the adsorbents were prepared through wetness impregnation method. The adsorbents were tested trough batch adsorption studies with several operating conditions such as initial metal ion concentration, adsorbent dosage, and contact time in order to evaluate their effect on adsorption process. The Atomic Adsorption Spectrophotometer (AAS) was then applied to determine the remaining of metal ions in sample solution. The results revealed that the removal efficiency of Pb(II) ions is the highest for Fe/C/C.S adsorbent at optimum condition (60 mg L-1 metal ion concentration, 1.5 g dosage, and 4 h of contact time). The equilibrium modelling showed that the sorption of Pb(II) was better fitted by Langmuir model for Fe/C/Al2O3 and Fe/C/M.S, while Freundlich model for Fe/C/C.S. Furthermore, the kinetic of adsorption of all adsorbents for Pb(II) better described by pseudo-second order kinetic model. The reusability testing of potential adsorbent (Fe/C/C.S) revealed that adsorbent are capable to employ up to four cycles. Meanwhile, the stability of adsorbent investigated using X-ray fluorescence (XRF) showed that adsorbent was stable. Furthermore, X-ray diffraction (XRD) study revealed the polycrystalline structure of adsorbents. Analysis trough nitrogen adsorption (NA) and field emission scanning electron microscopy (FESEM) showed that adsorbents are mesoporous with rough and uneven surface. Energy dispersive X-ray (EDX) analysis confirmed the presence of Al, C, O, Fe, Si, Ca elements in the adsorbents. Fourier transform infrared spectroscopy (FTIR) analysis revealed the presence of several functional groups on the adsorbents. Due to its removal efficiency, reusability, and stability, Fe/C/C.S adsorbent can be considered to be an economically advantageous material for treating Pb(II) ions from aqueous solution.