Removal of Pb(II), Zn(II), Cu(II) and Cd(II) from aqueous solutions by adsorption onto olive branches activated carbon: Equilibrium and thermodynamic studies

ISSN: 2410-9649 Alkherraz et al / Chemistry International 6(1) (2020) 11-20 iscientic.org. 12 www.bosaljournals/chemint/ editorci@bosaljournals.com lead, cadmium, copper, arsenic, mercury, nickel, etc., are nonbiodegradable, considerably toxic to humans and also leads to ecological imbalances (Benvenuti et al. 2017; Cardoso et al. 2017). These metals can reach the human body and results in brain and bone damage, nervous system damage, neurological disorders and even cancer (Rao and Khatoon, 2017). Various methods are used to remove heavy metals from industrial waste water, such as: solvent extraction, biological treatment, ionic exchange, adsorption on activated carbon, reverse osmosis, electrolytic methods and membrane filtration (Dursun et al. 2005; Elsherif et al., 2013a; 2013b; 2014a; 2014b; 2014c; Elsherif and Yaghi, 2016; 2017a; 2017b). Among these methods, the adsorption method is the simplest, cheapest, and fastest one for heavy metals removal and also applicable for lower concentration levels (Rodrigues et al., 2013; do Nascimento et al., 2019; Jaafari and Yaghmaeian, 2019; Londono-Zuluaga et al., 2019; Massoud et al., 2019; Moreira et al., 2019; Peng et al., 2019; Yin et al., 2019). Activated carbon is considered to be an effective method for heavy metals removal from polluted waste waters due to its higher surface area, microporosity, and high adsorption capacity (Hameed, 2008; Rodrigues et al. 2011). Activated carbon obtained from biosorbents has the desired surface area and pore volume and accordingly, it has emerged as a potential alternative for activated carbon production (de Sousa Ribeiro et al., 2017). In our previous work, we used olive leaves, coffee, tea, and orange peels powders as biosorbents for removing heavy metals from aqueous solutions (Elsherif et al., 2017a; 2017b; 2018a; 2018b; 2019). In the present study, factors affecting the biosorption efficiency of Pb(II), Cd(II), Zn(II), and Cu(II) onto activated carbon prepared from olive branches have been studied. Equilibrium studies using various models have been also investigated. Also, thermodynamic parameters of the system have also been determined. MATERIAL AND METHODS Chemical and reagents Lead(II) Nitrate, ACS Reagent, ≥99%, from Honeywell Fluka, Zinc(II) Nitrate Hexahydrate, 98%, Reagent grade, from Honeywell, Copper(II) Nitrate Hemi(Pentahydrate), 98.0 to 102.0%, ACS Reagent, from Honeywell Fluka, Cadmium(II) nitrate tetrahydrate, 98%, ACS Reagent, from Merck, were used to prepare 1000 mg/L stock solutions of metal ions and using double distilled water. Desired test solutions of metal ions were prepared using appropriate subsequent dilutions of the stock solution. The range of concentrations of metal ions prepared from standard solution varies between 50 and 750 mg/L. Before mixing the adsorbent, the pH of each test solution was adjusted to the required value with 0.1 M NaOH or 0.1 M HCl. Sodium hydroxide, BioXtra, ≥98% (acidimetric), pellets (anhydrous), from Merck and hydrochloric acid, ACS reagent, 37%, from Merck were used to prepare these solutions. Preparation of activated carbon Olive branches were collected from Misurata city in Libya. It was cleaned, dried, ground, activated with H3PO4, and then carbonized using the procedure reported by Isah et al. (Isah et al, 2015). The product was washed and filtered several times with distilled water and then subsequently dried in an oven at 70oC for 24 h.