Impact of Hardness on the Interaction of Zn(Ii) with a Fibrous Biosorbent, Panicum Maximum Dried Leaves

Abstract Environmental pollution is becoming increasingly problematic due to industrial expansion and population growth. As industrial effluents release pollutants harmful to various environmental compartments, including surface water, their removal from contaminated water using low-cost, natural adsorbents has gained much attention. This study focuses on the investigation of adsorption characteristics of dried leaves of Panicum maximum , a fibrous biosorbent, toward Zn(II) from water and the effect of water hardness on Zn(II)-biosorbent interaction, a novel aspect of biosorption research. The presence of functional groups in the biosorbent, determined by Fourier transform infrared spectroscopy, would promote its attraction toward Zn(II), and further, the availability of vacant sites, determined by scanning electron microscopy, provides strong evidence for trapping Zn(II). Interaction of Zn(II) on the biosorbent obeys the Langmuir adsorption isotherm better than the Freundlich adsorption isotherm according to linear regression analysis, indicating the initial monolayer coverage of the adsorbate. The maximum adsorption capacity determined under the optimum experimental conditions of shaking time, settling time, solution pH and adsorbent dosage is 9.9×10 3 mg kg − 1 , which is comparable to many other adsorption systems. The interaction between Zn(II) and the biosorbent is so strong that the extent of removal is not much influenced by variation of hardness of the medium up to 100 mg L − 1 CaCO 3 hardness and that a relatively high pseudo second order rate constant results in with a regression coefficient of 0.999. Therefore, this fibrous biosorbent has great potential for scaling up the proposed methodology for remediation of Zn(II) from contaminated industrial effluents.