Effective activated carbon as adsorbent for the removal of copper(II) ions from wastewater

Abstract

Nitric acid activated carbons prepared from the barks of Limonia acidissima plant (NALABC) and stems of Hibiscus cannabinus plant (NAHCSC) are investigated as adsorbents for the removal of Cu(II) ions from waste water using batch methods of extraction. Various extraction conditions namely, pH, time of equilibration, sorbent concentration, initial concentration of Cu(II) ions and temperature, are optimized for the maximum removal. Substantial amounts of Cu(II) are extracted in the pH range: 3 to 9 and adsorption capacities are 19.6 mg/g for NALABC and 29.4 mg/g for NAHCSC, which are more than many active carbons developed in the previous works. It is interesting to note that the adsorbents are effective in acidic, neutral and also in basic conditions of the water samples and thus paving the way for applying these adsorbents in wide pH ranges of diverse samples. Five-fold excess of common co-ions that are normally present in water, have marginally affected the % removal. Thermodynamic parameters are evaluated for the spontaneity and nature of adsorption processes. The adsorption phenomenon is analyzed using Langmuir and Freundlich isotherm models and noted that Langmuir isotherm model suits better indicating the uniform and mono-layer nature of adsorption. Kinetics of adsorption is analyzed and found that pseudo second-order kinetics preferably explains the adsorption of Cu(II). The spent NALABC and NAHCSC can be regenerated and subsequently used. The adsorbents developed are found to be effective in removing Cu(II) ions from the real water samples collected from polluted lakes and copper based industries.