371 Egypt. J. Chem. Vol. 64, No. 8 pp. 3981 - 3989 (2021) Egyptian Journal of Chemistry http://ejchem.journals.ekb.eg/ Modelling for removal of Cr(VI) and Pb(II) using sago bark (Metroxylon sagu) by fixed-bed column method Syiffa Fauzia1, Hermansyah Aziz2, Dahyunir Dahlan3, Rahmiana Zein1* 1Laboratory of Analytical Environmental Chemistry, Department of Chemistry,Andalas University, 25163, Padang, Indonesia 2Laboratory of Physical Chemistry, Department of Chemistry, Andalas University, 25163, Padang, Indonesia 3Laboratory of Material and Structure, Department of Physics, Andalas University, Padang, 25163, Indonesia Abstract Industries commonly produced a large scale of wastewater that consisted of hazardous materials such heavy metals. Recently, one of popular methods for wastewater treatment was adsorption system using biosorbent. Sago bark (Metroxylon sagu) was a solid waste remained from sago starch industry. It contained various functional group such as carbonyl and hydroxyl groups that could be utilized to resolve wastewater containing metal ions. Removal of Cr(VI) and Pb(II) using sago bark (Metroxylon sagu) have been investigated by a fixed bed column reactor. The effect of flow rate (2, 4, 6 mL/min) and bed depth (3, 6, 9 cm) was examined in order to observe column performance (15x1 cm id). The result revealed that the lower flow rate and the higher bed depth delayed the breakthrough time and exhaustion time. Thus, the optimum conditions were achieved at 2 mL/min of flow rate and 9 cm of bed depth for both metal ions. The equation of Thomas, BDST and Yoon-Nelson models was carried out to evaluate the breakthrough curve. The repeatability and regeneration of sago bark were analyzed by HNO3 0.01 M within 3 cycles. It means that sago bark has a promising ability to remove Cr(VI) and Pb(II) ions in solution. Keywords: adsorption; column continuous; Cr(VI); Pb(II); sago bark 1. Introduction and other harmful diseases [3–5]. Considering its Industrial growth has been contributed to negative effect, various methods have been conducted environmental issue due to the generation of either to treat heavy metal wastewater so that it is feasible to liquid or solid waste as secondary product after be discharged to the environment. One of them is industrial processing. Approximately, 1.15 tons waste adsorption. Adsorption is an accumulation of produced were not processed in Indonesia [1]. compound in the liquid/gas phase on the solid surface. Recently, heavy metal waste has become a threat to the This method utilizes an adsorbent commonly come wide world. Heavy metal exposure is able to defect the from waste such as agricultural waste or biomass for environment, animals, and human. These heavy metals example pensi shell [6], Neplhelium lappaceum [7], enter the human body through the food chain, water or Macrocystis pyrifera and Undaria pinnatifida [8], other daily activities. Heavy metal such as lead Swietenia Mahogani fruit shells [9], oil palm fibre (Pb(II)) and chromium (Cr(VI)) is presented in various [10], immobilized citrus peels [11], residue allspice industries like tanning, mining, batteries, [12] and so forth. All of the adsorbent mentioned electroplating, paint and so forth [2]. Pb(II) gather in above own the advantages of adsorption method. It is the body and poison biological activities of living low cost, easy to prepare, no secondary waste, efficient organism that harm kidney, liver, and etcetera. for the low metal ion concentration, and simple [9, 12]. Whereas, chromium in Cr(VI) oxidation state is highly The adsorption of Cr(VI) and Pb(II) using sago bark soluble rather than Cr(III) oxidation state. Cr(VI) (Metroxilon sagu) has been performed by previous forms a hexavalent chromium ion that highly toxic due research employing the batch system [13, 14]. The to its mobility that causes a mutagenic, carcinogenic batch system provides information regarding the _________________________________________________________________________________________________ * Corresponding author: [email protected] or [email protected] Receive Date: 27 November 2019, Revise Date: 02 April 2020, Accept Date: 08 April 2021 DOI: 10.21608/EJCHEM.2020.20172.2212 ©2021 National Information and Documentation Center (NIDOC) 3982 Syiffa Fauzia, et.al. _____________________________________________________________________________________________________________ equilibrium and kinetic mechanism. Unfortunately, In the bottom of a column, glass wool was attached to this system is unable to be applied to industrial prevent adsorbent loss during adsorption. The metal purpose because the volume treated is constant/limited solution was pumped by a peristaltic pump. The giving lower driving force and the gradient effluent was collected every 5 minutes for an hour. concentration does not exist [5, 15]. Therefore, the Metal ion concentration was measured by AAS column system is required to evaluate the adsorbent (Atomic Absorption Spectrophotometer). The efficiency through the breakthrough curve shape. The breakthrough time and exhaustion time were observed breakthrough performance implies the probability of by plotting Ce/Co Vs time (breakthrough curve). Sago adsorbent for industrial application [8, 9, 12]. The bark was characterized by FTIR (Fourier Transform previous research utilized stem tree of soybean to Infra-Red), SEM (Scanning Electron Microscopy), remove Pb(II) and Zn(II) has applied optimum and BET (Bruener Emmet-Teller). condition that was obtained from batch system in continuous flow system. The adsorption capacity for Column adsorption data modelling both Pb(II) and Zn(II) was 12.44 mg/g and 6.75 mg/g, Thomas model respectively [16]. Beside, sago bark was a solid waste The linearization of the Thomas model was derived by from sago starch industry which generated about 1.5 C plotting ln ( o − 1)vs t. Thomas model stated that the tons waste per day [17]. Therefore, it becomes a Ct concern to overcome this problem as well. The adsorption process was reversible based on the purpose of the present research is to investigate the second-order kinetic model with no axial dispersion efficiency of sago bark for Cr(VI) and Pb(II) removal [5, 18]. This model was represented by the following in fixed bed column. Some parameters are subjected to equation: C k q m evaluate the adsorbent performance such as flow rate ln ( o − 1) = TH o and bed depth. The breakthrough curve is described by Ct Q Thomas, BDST and Yoon-Nelson models. − kTHCot Equation (1) Where Co and Ct were initial concentration and 2. Experimental Section concentration of metal ion (mg/L) at the time (t). kTH was Thomas model constant (L/mg.min). qo and m Material and Adsorbent preparation were maximum adsorption (mg/g) and adsorbent mass Pb(II) and Cr(VI) solution were prepared by (g), respectively. Meanwhile, Q was flow rate dissolving Pb(NO3)2 and K2Cr2O7 in distilled water. (mL/min). NaOH or HCl was used to adjust solution pH. HNO3 Yoon-Nelson was employed as chemical activator of adsorbent and This model gave information regarding the time glass wool. All the reagents were analytical grade required for 50 % breakthrough. This model was purchased by Merk, Germany. Sago bark (Metroxylon simple due to no detailed parameters needed. The sagu) was collected from the local area, West Sumatra, Yoon-Nelson model was expressed by the given Indonesia. The sample was washed to remove dirt and equation: then sundried. Dried sago bark was crushed to get fine Co ln ( ) = kYNt − kYN Equation (2) size <160 µm. Sago bark powder was soaked in 0.01 Co − Ct -1 M HNO3 for an hour. Then, filtered and rinsed with Where kYN and were Yoon-Nelson constant (min ) distilled water until neutral pH. The powder was and time required at 50 % of breakthrough (min) [18, sundried to remove water. 19]. Fixed bed column procedure BDST (Bed depth service time) The fixed-bed column was carried out in a glass BDST model can be employed to the adsorption column (15 cm length and 1 cm inner diameter). Some process without further experiment. It can predict the parameters were studied to evaluate fixed-bed column service time of adsorbent before it has to be performance such as flow rate (2, 4, 6 mL/min), regeneration or replaced, the ability of adsorbent to adsorbent mass (0.5;1;1.5 g), and adsorption- adsorb the certain amount of adsorbate [5, 18]. The desorption cycles. pH and initial concentration of relationship of each parameter was determined by the metal ions have been studied in the batch system. following equat nion: These optimum conditions were employed to evaluate NoZ 1 C0 the ability of sago bark in column system since t = − ln [ − 1] Equation (3) Cou KaCo Cb dynamic system more practical in industry. Optimum conditions of Cr(VI) in the batch system were Where No and Z were bed adsorption capacity (mg/L) achieved at pH 3 and 1000 mg/L of Cr(VI) and bed height (cm), respectively. Ka was BDST concentration [14]. Whereas Pb(II) reached the peak at model rate constant (L/mg/min), u was the linear pH 5 and 800 mg/L of Pb(II) concentration [13]. ________________________________________________ Egypt. J. Chem. 64, No. 8 (2021) MODELLING FOR REMOVAL OF Cr(VI) AND Pb(II) USING SAGO BARK.. 3983 __________________________________________________________________________________________________________________ velocity (cm/min), t was service time (min) and Cb was properties as well such as the electronegativity, ionic the concentration at the breakthrough (mg/L). radii, hydrated ion radii and so forth. These metal properties were contributed to the interaction between 3. Results And Discussion an adsorbent and metal ion either physical or chemical sorption [2, 13, 14, 23]. Adsorbent characterization The bark surface is observed by FTIR and SEM. Flow rate effect Effect of flow rate was carried out based on optimum FTIR spectra give spectra of functional groups condition obtain in a batch system (pH 3, initial existing in sago bark.