Studies on the Effect pH on the Sorption of Pb(II) and Cu(II) ions from Aqueous Media by Nipa Palm (Nypa fruticans Wurmb)

The effect of pH on the sorption of Pb and Cu ion onto Nypa fruticans Wurmb biomass was investigated. Initial pH value of 2, 5, 7, 9, and 12 were used for this study with varying initial concentrations of metal ions. The experimental results were analyzed in terms of Langmuir, Freundlich and Flory-Huggins isotherms. The data showed that the maximum pH (pHmax) for the efficient sorption of Pb and Cu is 5.0. Evaluation using the Langmuir equation gave the monolayer sorption capacity as 91.0mg/g for Pb and about 61.0mg/g for Cu. The sorption of Pb and Cu ion is pH dependent and the data showed that Nypa fruticans wurmb biomass is a successful biosorbent for treating heavy metal contaminated wastewater. The thermodynamic assessment of the metal ions on Nypa fruticans wurmb gave negative ∆G values, which confirms the feasibility of the process and the spontaneous nature of the sorption. @JASEM The presence of toxic metals such as Pb and Cu in the environment has become a major threat to plants, animals and human life due to their bioaccumulating tendencies. It is an established fact that metals are also toxic to aquatic organisms, consequently, a number of projects objective for metal concentration in aquatic environment need to be proposed to protect the organisms. In light of the above, there has been an abundance of interest in removal of heavy metals from contaminated waste streams (Basta 1992, Godfredsen 1994, Horsfall et al 2004 and Jewel 1994). The conventional methods in existence for the removal of metals from waste streams such as precipitation, flocculation, reverse osmosis, etc are expensive and not economically feasible for small and medium scale industries prevalent in developing countries (Cheng 1994). There is the need therefore to develop alternative methods of sorption of metals using natural plant products as adsorbents, which are inexpensive and always available. Some natural materials that have been used for similar study include clay (Vinod and Anirudhan, 2001), Cassava waste (Abia et al 2003) and Medicago SativaAlfalfa (GardeaTorresday et al 1998). Presently no information is available on the use of Nypa Fruitcans wurmb biomass as a biosorbent for toxic metals from wastewater. Nypa fruitcans wurmb commonly called Nipa Palm, considered one of the most common palms in South-East Asia and now ravaging the mangroves of the Niger Delta Area of Nigeria is a swamp specie, which belongs to the PALMAE FAMILY (Gonzales, 1979). Nypa fruitcans wurmb possess chemical functional groups that are most likely responsible for metal binding and are inexpensive, easily obtained and is presently a nuisance and colonizing the mangroves of the Niger Delta Region. It may be a potential bioresource for extraction and recovery of toxic metals from contaminated waters. The principal aim of the present study is to investigate the effect of pH on the potential use of the biomass of Nypa fruitcans wurmb as novel biosorbent for toxic metals from aqueous media. MATERIALS AND METHODS Preparation and Activation of Biomass: The shoots of Nipa plant were obtained from the brackish waterfronts of the Niger Delta Area of Nigeria. The samples were cut into smaller sizes and washed with deionized water and then dried. Dried samples were ground and passed through the 100-mesh, screens using a Wiley mill. Determination of Pb and Cu Sorption as a Function of pH: 1.0 + 0.01g Nypa fruticans biomass was weighed into several flasks. Standard solutions of initial metal ion concentrations ranging from 2 to 10mg/l of Pb and Cu were prepared from stock solutions of PbSO4 and CuSO4 respectively. 50ml of the metal ion solutions in triplicate were added to the biomass. The pH of these suspensions were adjusted to 2.0, 5.0, 7.0, 9.0 12.0. The pH adjustments were made either by adding 2M HCl or 2M NaOH solution and the pH recorded as initial pH (pHin). The flasks were tightly stopped and the mixtures gently agitated on a Stuart shaker for 1 hour at 30C. At the end of shaking, the pH of the suspension was measured and recorded as the final pH (pHf) of each solution. The suspension was then filtered through Whatman No 45 filter paper and centrifuged at 2800 x g for 5 minutes. The metal content at each pHf was determined using flame atomic absorption Spectroscopy. Metal Content Analysis: The Pb and Cu content at each pH were determined with a Buck Scientific Flame Atomic Absorption Spectrometer (FAAS) model 300A. Analytical grade standards were used to calibrate the instrument, which was checked Studies of the pH Effect on the Sorption of Pb(II) and Cu(II) ions from Aqueous Media by Nipa Palm (Nypa fruticans Wurmb) * Corresponding author: Wankasi, D. 88 periodically throughout the analysis for instrument’s response. The batch experiments were performed in triplicates and the averages were computed for each set of values. Data Analysis: The amount of Pb and Cu sorbed by the biomass during the series of batch investigation were determined using a mass balance equation (Chu and Hashim, 2001) expressed as: ) ( e o e C C M V q − = ..........1 Where qe = metal concentration on the biomass (mg/g biomass) at equilibrium, Ce = metal concentration in solution (mg/dm) at equilibrium; Co = initial metal concentration in solution (mg/dm); V = Volume of initial metal solution used (dm); M = mass of biomass used (g). The sorption data was tested against Langmuir, Freundlich, and Flory Huggins adsorption isotherm models. The linear form of the Langmuir model as shown below was used.