THE FEASIBILITY OF SAGO BARK (Metroxylon sagu) IN Cu(II) REMOVAL: BATCH AND FIXED BED COLUMN EVALUATION

Abstract

The present study examines the ability of sago bark to remove Cu(II) ions in solution which was a solid waste from sago starch industry. The optimum condition utilizing batch experiment for Cu(II) sorption was achieved at pH 5, agitation speed 100 rpm, adsorbent mass 0.1 g, temperature 298 K, 800 mg/L of initial concentration in contact time 30 minutes with adsorption capacity 16.47 mg/L. Cu(II) removal showed a good agreement with Langmuir, Freundlich and Tempkin isotherm model. The kinetic data confirmed that Cu(II) sorption followed pseudo-secondorder model. The thermodynamic parameters revealed that the adsorption process was exothermic. Fixed bed column evaluation revealed that the best condition reached at 2 mL/min of flow rate with 9 cm bed depth. The breakthrough curve was suited to Thomas and Yoon-Nelson models. HNO3 0.01 M gave better performance as a desorbing agent and adsorption capacity decreased after 3 adsorption-desorption cycles. Keyword: Adsorption, Batch, Column, Cu(II), Sago Bark © RASĀYAN. All rights reserved INTRODUCTION The industrial process is discharged waste containing heavy metals. These metals contribute to environmental damage. The United Nations World Water Development stated that the amount of waste discharged to water bodies was 2 million tons of waste. Copper (Cu(II)) is one of the heavy metals that is abundance in the earth’s crust. Therefore, the occurrence of copper in the environment is both naturally and due to human activities. Human activities such as electroplating, herbicide, metal production, phosphate fertilizer production and paper industry are discharged an amount of copper to the air, water and soil. This metal ion can be accumulated or reacted to form a dangerous compound. Cu(II) is able to evoke some diseases to human body such as nausea, diarrhea, coma and death. That is why the level of Cu(II) in the drinking water level is limited by 1.3 mg/L. Due to its hazardous effect, the number of investigations has been conducted to overcome heavy metal wastewater. Adsorption is a common technique that has employed to remove heavy metals in wastewater. The adsorption technique can be done in two ways, the batch system and fixed-bed column system. The batch system gives information related to equilibrium and kinetic. Unfortunately, this system cannot be applied for industrial purpose but fixed-bed column. In the fixed-bed column, the waste flows continuously lead to gradient concentration that improves mass transfer and promotes adsorption efficiency. The adsorption technique is preferred because it is easy operation, high efficiency, low-cost and regeneration ability. The low-cost comes from the utilization of biomass or agricultural waste as adsorbent to remove heavy metals such as barley straw ash, stem tree of soybean, nypa fruticans merr shell , activated carbon from oak leaves and date palm Vol. 12 | No. 4 |1889 1900| October December | 2019 1890 SAGO BARK (Metroxylon sagu) IN Cu(II) S. Fauzia et al. dead leaflets, curry tree carbon, watermelon peel, rice husk, tree sawdust, natural and activated fluorapatite, zeolite, eggshell and sugarcane bagasse. These adsorbents consist of lignocellulosic which has pores, carboxylic and hydroxyl functional group playing a role in metal ion removal. Most of the adsorbents mentioned above came from agricultural or household waste. This waste would bring up another issue if it was not properly treated. Thus, the utilization of agricultural or household waste as an adsorbent will add more value toward them. Sago (Metroxylon sagu) is a plant that is used as raw material for starch production or livestock feed. These activities remain its bark as a waste that is not fully utilized. The bark has fiber that consists of lignin associated with the hemicelluloses. These compounds contain several functional groups that will support the adsorption of heavy metal. It expects to overcome both heavy metal in wastewater and sago bark itself as agricultural waste. The previous research which has been conducted in Pb(II) and Cr(VI) removal utilizing sago bark as the adsorbent confirmed the existence of pores, carbonyl and hydroxyl functional group that were one of the main requirements of biomass to be used an adsorbent. The result indicated that the ability of sago bark as an adsorbent was quite promising with adsorption capacity for Pb(II) and Cr(VI) removal 31.43 mg/g and 61.73 mg/g, respectively. Thus, the research aim is to evaluate the equilibrium and kinetics of chemically activated sago bark in Cu(II) removal using the batch system and investigated its feasibility in industrial purpose by following fixed-bed column system. EXPERIMENTAL Adsorbent Preparation Sago (Metroxylon sagu) bark was obtained from the local area of West Sumatra, Indonesia. Sago bark was cut up into small pieces and washed with distilled water. Then, it was dried under the sunshade to remove water. The dried pieces of sago bark were powdered and sieved using into the particular size by a manual sieve (Retsch milling and Sieving). Later the powder of sago bark was chemically activated by HNO3 0.01 M for 2 hours. The powder was rinsed until the pH is neutral. Then, let it dried for further use. Adsorbent Characterization The morphology of adsorbent was studied by Scanning Electron Microscopy (SEM, Hitachi S-3400N). The sago bark powder was placed on the sample holder and coated by gold particle using ion sputtering method. Then, the surface morphology was scanned at 10 kV with 1000 times magnification. The functional group existed in sago bark was observed by Fourier Transform Infra-Red (FTIR, Unican Mattson Mod 7000). Whereas, the chemical composition was analyzed using X-ray Fluorescence Spectroscopy (XRF, PANalytical Epsilon 3). Batch Study The Batch study was carried out at the various experimental conditions. 10 mL of Cu(II) solution, which the pH and concentration were varied within the range (2-7) and (20-1000 mg/L), contact time (5-90 minutes), different temperature (25-45 C) at adsorbent mass 0.1 g. After the adsorption process was over, the supernatant and adsorbent were separated by Whatman filter paper No. 42. The concentration of Cu(II) remained was measured using Atomic Absorption Spectrophotometer (AAS, AA240). Error bar represented the standard deviation. Fixed Bed Column Study The fixed-bed column study was conducted in a glass column (15×1 cm i.d.) by varying flow rate (2-6 mL/min) and bed depth (3-9 cm/0.5-1.5 g) with pH and concentration optimum obtained from batch system, 160 μm of particle size at room temperature. The effluent concentration was analyzed every five minutes using AAS and the breakthrough curve was plotting against Ce/Co vs time (t). Regeneration Study The repeatability of sago bark as adsorbent was investigated using HNO3 with concentration 0.1 M and 0.01 M as a desorbing agent. In the batch system, the regeneration study was conducted by contacting 10 Vol. 12 | No. 4 |1889 1900| October December | 2019 1891 SAGO BARK (Metroxylon sagu) IN Cu(II) S. Fauzia et al. mL of Cu(II) solution with an adsorbent at the optimum condition from the batch study. Meanwhile, for the fixed bed column study, the desorbing agent was streamed through the bed in the column. Later the Cu(II) concentration was determined by AAS. RESULTS AND DISCUSSION Sago Bark Characterization The FTIR spectra of sago bark before and after adsorption were reported in Fig.-1. A band at 3421.10 cm 1 corresponding to O-H stretching was shifted to 3422.62 cm after Cu(II) sorption (figure 1a) The peak at 1636.26 cm, shifted to 1637 cm represented a C=O (carbonyl) group. Whereas, the peak within the range of 1000-1200 cm assigned to C-O stretching or C-N stretching. The SEM image indicated that the surface of sago bark changed due to the adsorption process. The pore has disappeared because the adsorbate has attached to the adsorbent surface (Fig.-2a and b). Based on the previous research , the sago bark pore radii was 24, 904 Å and the hydrated ionic radii of Cu(II) was 4.19 Å. It explained that the feasibility of Cu(II) ion to trap in the sago bark pore. Along with the pore surface, the chemical composition of sago bark has changed as well. This proof that the Cu(II) has reacted with the sago bark not only physically (trap in the pore) but also chemically through complexion, ion exchange or electrostatic force because Cu(II) has 1.90 of electronegativity that supported electrostatic interaction. Fig.-1: FTIR spectrum of Sago Bark (a) Before Adsorption, (b) Cu(II) Uptake Vol. 12 | No. 4 |1889 1900| October December | 2019 1892 SAGO BARK (Metroxylon sagu) IN Cu(II) S. Fauzia et al. Fig.-2: SEM Morphology of Sago Bark (a) Before adsorption, (b) Cu(II) Uptake Table-1: The Chemical Composition of Sago Bark Before Adsorption After Adsorption Compound Concentration (%w/w) Compound Concentration (%w/w) Ca 16.10 Ca 15.97 K 7.81 K 1.88