Songklanakarin J. Sci. Technol. 35 (2), 227-233, Mar. - Apr. 2013 http://www.sjst.psu.ac.th Original Article Phytoremediation of synthetic wastewater by adsorption of lead and zinc onto Alpinia galanga Willd Vanida Chairgulprasert1*, Aumikansung Japakeya2, and Haseenah Samaae2 1 Department of Science, Faculty of Science and Technology, 2 Department of Education, Faculty of Education, Prince of Songkla University, Pattani Campus, Mueang, Pattani, 94000 Thailand. Received 6 September 2012; Accepted 14 February 2013 Abstract Adsorption of Pb(II) and Zn(II) from aqueous solution onto a phytosorbent mixture of galangal (Alpinia galanga Willd) leaves and pseudostem has been investigated in a batch system. Removal efficiency was optimized with respect to pH, contact time, initial Pb(II) and Zn(II) concentration and phytosorbent dosage. Galangal exhibited a higher adsorption efficiency for lead (95.2%) than for zinc (66.9%). Both lead and zinc equilibrium sorption data were better represented by the Freundlich isotherm than the Langmuir isotherm and in each case followed second order kinetics. Keywords: galangal, heavy metal, adsorption isotherm, adsorption kinetics, phytosorbent 1. Introduction leaves, wheat bran, orange peel, and both banana pith and peel. However, the efficiency of metal adsorption by plant Heavy metals are amongst the most dangerous pollu- matter is affected not only by the quantity and dosage of tants of groundwater, (Briggs, 2003; Samuding et al., 2009; adsorbent, but also by pH, contact time, temperature and Momodu and Anyakora, 2010) industrial wastewater metal concentration (Brown et al., 2000; Demirbas, 2008; (Ziemacki et al., 1989; Sa’idi, 2010; Kapungwe, 2011) and Ngah and Hanafiah, 2008; Sud et al., 2008; Farooq et al., marine environments (Krishna et al., 2003; Boran and Altinok, 2010). The optimum parameters for metal adsorption vary 2010; Nubi et al., 2011). Because metal ions are not degrad- widely from one phytosorbent to another, so the effect of able, they have a tendency to accumulate in water streams, each of these factors must be determined when a plant by- endangering human health. Many treatment methods for the product is investigated as a metal adsorbent. removal of heavy metals have been proposed, including ion Galangal, (Alpinia galanga Willd) is a rhizomatous exchange, adsorption onto activated carbon, chemical preci- herb in the ginger family (Zingiberaceae) which is distributed pitation and membrane processes (Sud et al, 2008; Demirbas, throughout Thailand and Southeast Asia. The plant has a 2008). However, removal of metals from aqueous solution by distinctive aroma, resulting from the presence of essential oils plants is particularly interesting as plants are environment- and phenolic compounds (Jirovetz et al., 2003; Chudiwal et ally safe and socially acceptable (Ngah and Hanafiah, 2008; al., 2010; Wungsintaweekul et al., 2010). However, only the Miretzky and Cirelli, 2010). Various forms of horticultural rhizomes are widely used as a food additive and in herbal and agricultural waste have been investigated as potential medicine. As herbal remedy, galangal rhizomes act as a adsorbents for heavy metals, including bael and cypress carminative, and also treat rheumatism, spleen pain, bronchi- tis, diabetes mellitus and loss of appetite (Chan et al, 2008). However, the leaves and pseudostem are usually discarded * Corresponding author. as waste products of the food and herbalism industries. This Email address: [email protected] report shows our research into the phytosorption of lead and 228 V. Chairgulprasert et al. / Songklanakarin J. Sci. Technol. 35 (2), 227-233, 2013 zinc from aqueous solution using the leaves and pseudostems Variation sets were established to experimentally of A. galanga, an application which could raise the value of evaluate the optimum pH, contact time, metal ion concentra- the galangal plant. The optimum conditions of pH, contact tion and dosage. Each experiment was conducted according time, initial metal concentration and dosage of phytosorbent to a separate batch system using the parameters described in are also shown. Table 1. All experiments were carried out in triplicate. Only average values were reported, as the maximum error did not 2. Materials and Methods exceed 5%. 2.1 Preparation of phytosorbent materials 2.4 Metal adsorption The leaves and pseudostem of galangal were collected The metal ion uptake capacity of the galangal phyto- from Pattani Province, Thailand. They were used in the form sorbent (qt, mg/g) was calculated from Equation 1. of a phytosorbent powder for the removal of Pb(II) and Zn(II) from aqueous solution. The galangal powder was prepared qt = (Ci-Ct)V/W (1) by washing the leaves and pseudostems with distilled water, and then oven drying them at 70°C for 12 hrs. The dried where Ci and Ct (mg/mL) are the initial and final metal ion galangal was then ground and sieved through a 40 mesh concentrations in the filtrate, respectively. V (mL) is the filter to give particles of < 0.42 mm, and stored in an air tight volume of the solution and W (g) is the mass of galangal plastic container for further experiments. phytosorbent used. The percentage uptake (% Sorption) was determined 2.2 Preparation of synthetic wastewater from Equation 2. Single metal solutions of Pb(NO3)2 and Zn(NO3)2 were Sorption (%) = [(Ci-Ct)/ Ci]*100 (2) used to prepare the synthetic wastewater test solutions. They were prepared by diluting with deionized water to the 3. Results and Discussion desired concentrations. The acidity of each solution was adjusted to give a range of values between pH 2 and 7 by 3.1 Effect of pH addition of either 1 M hydrochloric acid or 1 M sodium hydroxide. The pH optimization study was carried out using 0.5 g phytosorbent/50 mL synthetic wastewater to adsorb Pb(II) 2.3 Batch phytosorption studies and Zn(II) at an initial concentration of 20 mg/L within a pH range of 2-7 for 60 min. Pb(II) and Zn(II) adsorption All experiments were performed in 100 mL Erlenmeyer improved as the pH was raised from 2 to 4. However, above flasks at room temperature and the flasks were agitated on a pH 4 the adsorption only increased marginally and reached mechanical shaker at 125 rpm throughout the study. Initial an optimum value at pH 6 for Pb(II) and pH 7 for Zn(II) (Table testing was carried out with 50 mL samples adjusted to pH 2, 2). Similar variations in adsorption behavior with solution pH at an initial metal concentration of 20 mg/mL. Powdered have already been reported for phytosorbents (Quek et al., galangal phytosorbent (0.5 g) was then added and the sus- 1998; Dhakal et al., 2005; Homagai et al., 2009 and Chakra- pension was shaken for 60 min. After shaking, the suspension varty et al., 2010). Effective adsorption of Pb(II) and Zn(II) was centrifuged and filtered under vacuum. The residual occurred in the pH range 4-7. At low pH, it is likely that an metal ion in the filtrate was analyzed using atomic adsorp- association between the adsorbent surface and hydronium tion spectroscopy (Perkin Elmer Analyst 100). ions occurs, giving rise to a repulsive force between the Table 1. Parameters used in the adsorption assessment with galangal. Effect pH Contact time (min) Dose (g) Initial concentration (mg/L) pH Pb 2,3,4,5,6,7 60 0.5 20 Zn 2,4,5,6,7 60 0.5 20 Time Pb 6 30,60,90,120,150,180 0.5 20 Zn 7 30,60,90,120,150,180 0.5 20 Dose Pb 6 150 0.5,1.0,1.5,2.0 20 Zn 7 60 0.5,1.0,1.5,2.0 20 Concentration Pb 6 150 0.5 10,20,30,40,50 Zn 7 60 0.5 10,20,30,40,50 V. Chairgulprasert et al. / Songklanakarin J. Sci. Technol. 35 (2), 227-233, 2013 229 Table 2. Effect of pH on removal of lead and zinc ions by galangal. Removal of Pb(II) Removal of Zn(II) pH qt (mg/g) sorption (%) qt (mg/g) sorption (%) 2.0 1.48 ± 0.01 74.11 ± 0.75 nt Nt 4.0 1.85 ± 0.03 92.52 ± 1.87 1.20 ± 0.00 60.22 ± 0.21 5.0 1.85 ± 0.02 92.38 ± 1.10 1.23 ± 0.00 61.41 ± 0.79 6.0 1.90 ± 0.07 95.09 ± 3.56 1.28 ± 0.02 64.73 ± 1.87 7.0 1.91 ± 0.01 95.24 ± 0.21 1.34 ± 0.04 66.93 ± 2.75 nt. = not tested adsorbent and the metal cation. As the pH increases the con- observed for Pb(II). The adsorption rate not only depends on centration of hydronium ions in solution decreases, and the the structure and chemical properties of the adsorbent, but binding between the active sites of the adsorbent and metal also on the coordination number and initial concentration of ions is enhanced. Additionally, acidic functional groups in the metal, the solution pH, the adsorbent dose and the tem- phytosorbents begin to dissociate in the pH range 4-7, giving perature. The complexity of the parameters influencing metal rise to multiple negative charges on the adsorbent surface. adsorption give rise to wide variations in optimal contact The resulting electrostatic attraction / complexation between time (Nasernejad et al, 2005; Li et al., 2008; Deviprasad and the surface and metal ions in solution may play a significant Abdullah, 2009; Karthika et al, 2010) such as those observed role in metal binding (Feng and Aldrich, 2004; Hashem, 2007). for Pb(II) and Zn(II). Several previous reports have revealed variations in the opti- Lagergren’s pseudo-first order equation was used to mal pH for removal of lead and zinc ions by phytosorbents.