School of Environmental Engineering, Universiti Malaysia Perlis, Kompleks Pusat Pengajian Jejawi 3, Arau, Perlis, Malaysia

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1 Fe(II) Biosorption using Pleurotus Spent Mushroom Compost as Biosorbent under Batch Experiment Ain Nihla Kamarudzaman 1, 2a, Tay Chia Chay 3,b, Amnorzahira Amir 1,c and Suhaimi Abdul Talib 1,d 1 mybiorec,institute for Infrastructure Engineering & Sustainable Management, Faculty of Civil Engineering, Universiti Teknologi MARA, 445 Shah Alam, Selangor, Malaysia 2 School of Environmental Engineering, Universiti Malaysia Perlis, Kompleks Pusat Pengajian Jejawi 3, 26 Arau, Perlis, Malaysia 3 Faculty of Applied Sciences, Universiti Teknologi MARA, 26 Arau, Perlis, Malaysia a ainnihla@unimap.edu.my, b taychiay@gmail.com, c amnorzahira@salam.uitm.edu.my, d ecsuhaimi@salam.uitm.edu.my Keywords: Biosorption; Fe(II) removal; Pleurotus spent mushroom compost; Batch Study Abstract. A laboratory study was conducted to optimize the various parameters involved in Fe(II) biosorption under batch experiment and also to evaluate the biosorption performance using Pleurotus spent mushroom compost as biosorbent. The optimum Fe(II) biosorption was achieved at an initial ph 5, contact time of minutes and initial Fe(II) concentration of mg/l using.75 g biosorbent dosages. The experimental data showed that Fe(II) biosorption onto Pleurotus spent mushroom compost were well fitted with Langmuir isotherm model and a pseudo-second order kinetic model. The study concluded that the Pleurotus spent mushroom compost was capable for removing of Fe(II) from aqueous solution. Introduction Heavy metal pollution is a major environmental problem. Release of heavy metals into the environment without proper treatment poses a serious threat to the environment and public health. It is noticeable that heavy metals are commonly present in the industrial wastewater especially from electroplating, mining, textile, metal refineries, automotive and other industries [1, 2]. Most of these activities generate large amount of wastewater which contains heavy metals in high concentration. Iron (Fe) is one of the most abundant elements found in nature and it is widely used in industrial applications. It is an essential element of human life in small quantities, but becomes toxic if their concentration increases above a certain minimum level [3]. The excessive exposure of iron on human may cause respiratory problems, heart attack, seizures, tissue damage and depression [4, 5]. The World Health Organization (WHO) limits the maximum concentration of iron in drinking water at.3 mg/l [6]. In Malaysia, the National Water Quality Standards (NWQS) set the maximum permissible concentrations of iron for Class IIA/Class IIB at 1. mg/l [7]. Therefore, it is necessary to remove heavy metals such as iron from industrial wastewater before it being discharged into the receiving environment. Conventional methods such as chemical precipitation, electrochemical, adsorption, membrane filtration, photocatalysis, ion exchange, phytoremediation, chemical oxidation and reduction have been applied for industrial wastewater treatment [8, 9]. However, for the past two decades, biosorption techniques have been found to be superior for heavy metals removal compared to other techniques in terms of cost, design, ease of operation and insensitivity to toxic substances []. Biosorption can be defined as the passive uptake of toxicants by dead or inactive biological materials or materials derived from biological sources [11]. The mechanisms responsible for the overall biosorption process may include adsorption, ion exchange, microprecipitation, complexation and chelation [11, 12, 13].

2 The main objective of the study was to optimize and evaluate the biosorption performance of Fe(II) removal using Pleurotus spent mushroom compost in batch experiments under varying conditions such as initial ph, contact time and initial Fe(II) concentration. Materials and Methods Preparation of Biosorbent. The sample of Pleurotus spent mushroom compost was collected from C & C Mushroom Cultivation Farm Sdn. Bhd., Johor, Malaysia. The sample was autoclaved (Hirayama HVE-5) at 121 C, under pressure of 18 psi for 15 minutes and then dried in an oven at 6ºC for 48 hours. The dried sample was ground and sieved to the particle size of less than 7 μm. After that, it was washed three times using ultrapure water to remove contaminants and impurities. Finally, the sample was dried in an oven at 6 C and kept in the drying cabinet. Preparation of Fe(II) Solutions. A stock solution of mg/l Fe(II) was prepared by dissolving g analytical grade iron sulfate heptahydrate (FeSO 4.7H 2 O) with ultrapure water and make to volume in a 5 ml volumetric flask. It was further diluted to obtain required concentrations. Biosorption Study. The batch experiments were conducted by adding.75g of Pleurotus spent mushroom compost into Erlenmeyer flasks containing 5 ml and 5 mg/l of Fe(II) solutions. Then, the flasks were placed in an incubator shaker and operating at 125 rpm for 6 minutes and temperature of 25± 1ºC. The operating parameters of initial ph 2-5, contact time of 5 6 minutes and initial Fe(II) concentration of mg/l have been examined. After biosorption, the samples were filtered through Advantec 5C filter paper with a pore size < 5 μm. The filtrates were later analyzed using Inductively Coupled Plasma Atomic Emission Spectroscopy (Perkin Elmer 7DV). All batch biosorption studies were conducted in duplicate. Biosorption Performance. The biosorption performance was evaluated based on the biosorption efficiency. The following equation was used to calculate the biosorption efficiency. (1) Where, C o is the initial heavy metal concentration (mg/l), C f is the final heavy metal concentration (mg/l). The experimental data were fitted to the linear Langmuir plot of C e /q e versus C e. (2) Where, q e is the heavy metal uptake at equilibrium (mg/g), q max is the maximum biosorption capacity (mg/g), C e is the heavy metal concentration at equilibrium (mg/l) and b is the Langmuir constant (L/mg). The Fe(II) biosorption was calculated from the pseudo-second order kinetic. (3) Where, q t is the heavy metal uptake at time (mg/g), t is time (minute) and k 2 is the rate constant of pseudo-second order (g/mg/min). Results and Discussion Effect of Initial ph. The influence of initial ph on the biosorption of Fe(II) by Pleurotus spent mushroom compost was studied at ph 2 to 5. As shown in Fig. 1, the biosorption efficiency of Fe(II) is ph dependent. It was increased from.3% to 5% by increasing the initial ph from ph 2 to 5. The initial ph plays a major role in biosorption process and highly influence the solution chemistry of Fe(II)

3 Biosorption Effeciency, Fe(II) (%) and also the surface charge of the biosorbent [14]. At low initial ph, the high H + ions concentration in the solution was competed with Fe 2+ ion for binding sites on the biosorbent surface [1]. Furthermore, higher H + concentration caused the biosorbent surface become more positive charged (protonated). The charge repulsion occurred between the biosorbent surface and Fe(II) ion and thus, resulting in reduction of Fe(II) biosorption [14, 15]. However, as the initial ph increases, the biosorbent surface has higher negative charged (deprotonated) and the charge attraction between the biosorbent and Fe(II) ion was also increased. However, at very high ph (ph > 6) the hydroxide ions (OH - ) favors to react with Fe(II) via precipitation and complexation to form Fe(OH) 2 and thus, reduced removal due to biosorption [16]. The optimum ph solution for biosorption of Fe(II) by Pleurotus spent mushroom compost was observed at ph 5. The similar ph trends also have been reported in Fe(II) biosorption study by [16, 17]. Therefore, the subsequent experiments were conducted at ph 5. Effect of Contact Time. The influence of contact time on the Fe(II) biosorption by Pleurotus spent mushroom compost is shown in Fig. 2. It was observed that the Fe(II) biosorption occurred most rapidly during initial stage (5 min) and reached the equilibrium phase within - min. About 46% of Fe(II) were removed from the solution after minutes. It proved that the active binding sites of Pleurotus spent mushroom compost are easily occupied by Fe(II) ion [15]. Based on these observations, the subsequent experiment was conducted under equilibrium phase with minutes contact time. 6 5 Biosorption Efficiency, Fe(II) (%) 5 4 Biosorption Efficiency, Fe(II) (%) ph Time (Min) Fig. 1: Effect of initial ph on Fe(II) biosorption (Fe(II) concentration: 5 mg/l; biosorbent dosage:.75 g; agitation speed: 125 rpm; temperature: 25ºC; contact time: 6 minutes) Fig. 2: Effect of contact time on Fe(II) biosorption (Fe(II) concentration: 5 mg/l; biosorbent dosage:.75 g; agitation speed: 125 rpm; temperature: 25ºC; ph: 5) Initial Fe(ll) Concentration (mg/l) Fig. 3: Effect of initial Fe(II) concentration on Fe(II) biosorption (Biosorbent dosage:.75 g; ph: 5; agitation speed: 125 rpm; temperature: 25ºC; contact time: minutes)

4 Initial Fe(II) Concentration. The influence of initial Fe(II) concentration on the biosorption of Fe(II) by Pleurotus spent mushroom compost is shown in Fig. 3. The biosorption efficiency of Fe(II) was increased from 35% to 77.2% when the initial Fe(II) concentrations reduces from mg/l to mg/l. This due to at lower Fe(II) ion concentrations, the ratio of binding sites to the moles of Fe(II) in the solution is high and hence all Fe(II) ions may interact with the biosorbent and removed from the solution. However, at higher concentrations, the binding sites available for sorption become fewer compared to the moles of Fe(II) present and hence, the removal of Fe(II) is strongly dependent upon the initial Fe(II) concentration [11]. Langmuir Isotherm and Pseudo-second Order Kinetic Model. Fig. 4 shows the Langmuir isotherm plot for Fe(II) biosorption onto Pleurotus spent mushroom compost. The maximum biosorption capacity, the Langmuir constant, b and R 2 values based on Langmuir isotherm model were 2.92 mg/g,.75 L/mg and.9949 respectively. Fig. 5 shows the pseudo-second order kinetic for Fe(II) biosorption. The value of qe, pseudo-second order rate constant, k 2 and R 2 value based on the slope and intercept calculation were 1.61 mg/g, 1.98 g/mg/min and.9996 respectively. The theoretical qe value of 1.61 mg/g was in agreement with the experimental value of 1.6 mg/g. Therefore, the experimental data were well fitted with the Langmuir isotherm model and a pseudo-second order kinetic model. It is indicated that a monolayer of Fe(II) ions was adsorbed on homogeneous biosorption sites on the surface of Pleurotus spent mushroom compost [18]. Ce/qe (g/l) Ce (mg/l) t/qt (min g mg-1) t (Min) Fig. 4: Langmuir isotherm plot for Fe(II) biosorption onto Pleurotus spent mushroom compost Fig. 5: Pseudo-second order kinetic for Fe(II) biosorption onto Pleurotus spent mushroom compost Conclusion In this study, Pleurotus spent mushroom compost biosorbent was successful for the biosorption of Fe(II) from aqueous solution. The study reveals that the Fe(II) biosorption performance is strongly influenced by various parameters such as initial ph, contact time and initial Fe(II) concentration. The optimum Fe(II) biosorption was achieved at initial ph 5, minutes of contact time and mg/l of initial Fe(II) concentration. In the future, in order to improve the biosorption study, the effect of other parameters such as particle size of biosorbent, agitation speed, temperature and the presence of other metals on the Fe(II) biosorption also can be investigated. Acknowledgements We are grateful for the university resources provided by Universiti Teknologi MARA, Malaysia. Special acknowledge to the Ministry of Education (MOE), Malaysia for granting us financial support under the Long Term Research Grant (LRGS) (3/PKT/674).

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