Scholarly article on topic 'Treatment of palm oil mill effluent by electrocoagulation with presence of hydrogen peroxide as oxidizing agent and polialuminum chloride as coagulant-aid'

Treatment of palm oil mill effluent by electrocoagulation with presence of hydrogen peroxide as oxidizing agent and polialuminum chloride as coagulant-aid Academic research paper on "Chemical sciences"

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{Electrocaogulation / "Palm oil mill effluent" / "Current density" / "Electrode material" / "Hydrogen peroxide" / "Polialuminum chloride"}

Abstract of research paper on Chemical sciences, author of scientific article — Mohd Nasrullah, Lakhveer Singh, Zahari Mohamad, Siti Norsita, Santhana Krishnan, et al.

Abstract The purposes of this study were to investigate the effects of operating parameters, such as electrode material, current density, percentage of hydrogen peroxide and amount of polialuminum chloride (PAC) on chemical oxygen demand (COD) removal of palm oil mill effluent (POME). The current density was varied between 30–80mAcm−2, PAC (1–3gL−1) as coagulant-aid and 1 and 2% of hydrogen peroxide as an oxidizing agent. As for the performance of electrode type, iron was more effective than aluminum. It appeared that the removal of COD increased with the increased of current density. When PAC and H2O2 increased, the percent of COD removal was increasing as well. The overall results demonstrate that electrocoagulation is very efficient and able to achieve more than 70% COD removal in 180min at current density 30–80mAcm−2 reliant upon the concentration of H2O2 and PAC.

Academic research paper on topic "Treatment of palm oil mill effluent by electrocoagulation with presence of hydrogen peroxide as oxidizing agent and polialuminum chloride as coagulant-aid"

Water Resources and Industry 17 (2017) 7-10

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Water Resources and Industry

journal homepage: www.elsevier.com/locate/wri

Treatment of palm oil mill effluent by electrocoagulation with presence of . m > hydrogen peroxide as oxidizing agent and polialuminum chloride as coagulant-aid

Mohd Nasrullah, Lakhveer Singh, Zahari Mohamad, Siti Norsita, Santhana Krishnan, Norul Wahida, A.W. Zularisam*

Faculty of Engineering Technology, Universiti Malaysia Pahang (UMP), Lebuhraya Tun Razak, 26300 Gambang, Kuantan, Pahang, Malaysia

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ARTICLE INFO

Keywords: Electrocaogulation Palm oil mill effluent Current density Electrode material Hydrogen peroxide Polialuminum chloride

ABSTRACT

The purposes of this study were to investigate the effects of operating parameters, such as electrode material, current density, percentage of hydrogen peroxide and amount of polialuminum chloride (PAC) on chemical oxygen demand (COD) removal of palm oil mill effluent (POME). The current density was varied between 3080 mA cm-2, PAC (1-3 g L-1) as coagulant-aid and 1 and 2% of hydrogen peroxide as an oxidizing agent. As for the performance of electrode type, iron was more effective than aluminum. It appeared that the removal of COD increased with the increased of current density. When PAC and H2O2 increased, the percent of COD removal was increasing as well. The overall results demonstrate that electrocoagulation is very efficient and able to achieve more than 70% COD removal in 180 min at current density 30-80 mA cm-2 reliant upon the concentration of H2O2 and PAC.

1. Introduction

Palm oil industry is one of the largest international agro-based industries. A number of operating processes are involved in order to extract palm oil from the fruit of E. guineensis such as sterilization, stripping, digestion, pressing, classification, purification, and vacuum drying [1]. This industries are of fundamental economic importance for Malaysia over the last three decades. However, this important industrial activity generates an enormous amount of environmental pollution in term of POME [2]. POME is characterized as a thick liquid, brownish in colour, rich in organic matter and unpleasant odour [3]. This highly polluted wastewater if not treated properly then discharge to the waterbody, it definitely will cause considerable environmental harms due to its high chemical oxygen demand (COD) of 50,000 mgL-1, biological oxygen demand (BOD) of 25,000 mg L-1, oil and grease (O&G) of 8,000 mgL-1, suspended solids (SS) of 20,000 mg L-1, and total solid of 40,000 mg L-1[4].

Several different techniques have been reported in the literature regarding on treatment of POME such as: anaerobic digestion [5-8], aerobic oxidation based on an activated sludge process [9], anaerobic and aerobic digest ions [10], chemical flocculation and coagulation [11,12], membrane anaerobic system [13], up-flow anaerobic sludge fixed film (UASFF) reactor [14], immobilized up-flow anaerobic sludge

blanket (UASB) reactor [15] and adsorption [16]. Although aforementioned treatment technique can be applied as the efficient methods, either they took a long period or needed a large amount of substance, both ways are less effective in treating this type of wastewater where it requires a short time treatment and an environmental compatibility with less chemical effect.

Recent study has demonstrated that electrocoagulation method deals an interesting option to conventional techniques in wastewater treatment, especially from sewage [17], textile [18,19], dye [20-24], tannery [25], olive mill [26], and paper industry [27]. In this process, electrode metal species generates metal ion upon the application of a direct current then hydrolysed in the electrochemical cell to produce metal hydroxide according to reaction (1)-(7).

At the cathode:

2H2O + 2e- H2 + 2OH- (1)

By using iron as electrode.

At the anode:

Fe ^ Fe2+ + 2e- (2)

In the solution (with dissolved oxygen):

* Corresponding author. E-mail addresses: zularisam@ump.edu.my, zularisam@gmail.com (A.W. Zularisam).

http://dx.doi.org/10.1016/j.wri.2016.11.001

Received 24 August 2016; Received in revised form 19 October 2016; Accepted 20 November 2016 2212-3717/ © 2016 The Authors. Published by Elsevier B.V.

This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/BY-NC-ND/4.0/).

Fe2+ + 2OH- Fe(OH)2 Fe2+ ^ Fe3+ + e-

Fe3+ + 3OH- Fe(OH)3

By using aluminum as electrode. At the anode:

Al ^ Al3+ + 3e-

In the solution (with dissolved oxygen):

Al3+ + 3OH- Al(OH)3

(6) (7)

This technique has some advantages such as less retention time, rapid sedimentation of electrogenerated flocs, less sludge production, absence or less of additional chemicals, simple equipment and easy to operate. However, by dealing with POME wastewater which contain high concentration of COD, the needs of additional application have to be done to enhance this treatment process. The study of hybrid treatment of POME by using electrocoagulation-chemical coagulation-oxidizing agent has not yet been studied. This study determined the treatability of POME by electrocoagulation method using two types of electrodes (iron and aluminum) accompanying with additional application of hydrogen peroxide as oxidizing agent and PAC as coagulant aid that would be practicable in use for small and medium size facilities.

2. Materials and methods

Fresh POME was collected from the receiving tank of an oil palm mill in Kilang Sawit Lepar Hilir 3 Pahang, Malaysia which be kept at 48 °C prior to use. The POME was fully characterized, as shown in Table 1.

A schematic diagram of the experimental set-up is depicted in Fig. 1. The electrochemical unit consists of an electrocoagulation cell, a D.C power supply and the electrodes (aluminum and iron). There are two monopolar electrodes having same dimension (120 mmx100 mmx2 mm) as an anode and a cathode which spacing of 10 mm between each other. The total effective electrode was 1.652x10-2 m2. In order to maintain an unchanged composition and avoid the association of the flocs in the solution, the stirrer was turned on and set at 80 rpm. The Reynolds number of the fluid solution is 2149.33. All the electrodes were washed with dilute HCl before every experiments conducted. At the beginning of each experiments, 1000 mL of POME wastewater was fed into the electrocoagulation cell and a certain amount of current was applied to the circuit for 240 min. The amount of current densities that have been applied to the system were 30, 40, 50, 60, 70 and 80 mA cm-2 with initial voltage of 6 V. Every experiment was performed at the room temperature. Experimentalsampleswere takenat specific intervalsofeach run for

Table 1

Characteristics of POME.

Parameter Concentration

Biochemical oxygen demand (BOD) 15,600

Chemical oxygen demand (COD) 25,000

pH 3.6

Total carbohydrate 10,000

Total nitrogen 800

Ammonium-nitrogen 20

Total phosphorus 90

Phosphorus 14

Oil and grease 2000

Total solid 20,000

Volatile suspended solids 4500

Fig. 1. A schematic diagram of the experimental set-up.

COD measurement.

The reagent grade of chemicals was used without further purification in every experiment. PAC was used as additional coagulant and hydrogen peroxide (H2O2) as the oxidation agent. There was unnecessary to apply any electrolyte supportive since the conductivity of POME (15.68 mS cm-1) was already high. The pH value was determined by a pH meter (Hanna, HI2211-02). The COD values were measured by a colorimetric method using Hach DR5000 spectrophotometer after sample's digestion using Hach COD Digestion Reagent. The system's current was provided by a regulated DC power supply (EDU-LABS TPR-3030D; 30V/30A) and was determined by a multimeter (Uni-T, UT203 multimeter).

3. Result and discussion

Preliminary experiments show that the removal's percentage of COD was 86.67% in 180 min of electrolysis. The percentage of COD removal can be deliberated as the core performance benchmark in this study. A number of experimental runs were conducted to determine the appropriate operating conditions, such as electrode material, EM (aluminum or steel); current density, i (Am-2); the concentration of hydroxides [H2O2] % and coagulant-aid [PAC], (gL-1). COD removal efficiency RECOD (%) was evaluated in order to monitor the performance of the system. The COD removal efficiency was determined as:

recod (%)'-

COD0 -

All values are in mgL 1 except for pH

where CODo is the initial amount of COD (mgL-1) and COD t is amount of COD (mgL-1) at the specific time.

Electrode assembles as the heart of the EC process and for that reason, it is very concern to find the suitable material selection. Iron and aluminum are the material that most commonly used in EC process as they are economic, readily available, and proven to treat wastewater effectively. In that case, the two materials were used in this study. The comparison of COD removal efficiency between iron and aluminum electrodes under the same conditions was showed in Fig. 2. By using iron electrode, COD removal efficiency reach its optimum level of 86.67% in just 180 min of electrolysis time as compared to the 81.11% in 210 min by using aluminum electrode. In the first 90 min, the graph shows more than half of COD concentration reduce for both type of electrode used, which the removal efficiency of 66.19% and 53.02% for iron and aluminum electrodes, respectively In electrocoa-gulation process, the dissolution of aluminum and iron electrodes, form a range of coagulant species which are metal hydroxides or polymeric metal hydroxides, that can destabilize and aggregate the suspended particles or precipitates to become flocs and absorb dissolve organic particles [28]. The metal hydroxide flocs can also remove wastewater through enmeshment or sweep coagulation [29]. In this case, even though both of the materials are rather effective, iron electrode showed a better performance than aluminum. The observa-

M. Nasrullah et al. 100 -

0 30 60 90 120 150 180 210 240

Time, min

Fig. 2. The variation of final COD removal efficiency for different electrode materials. i=70 mA cm-2, [PAC]=0 gL-1 and [H2O2]=0%.

tions of the structure of the iron sludge and aluminum sludge after electrocoagulation, using the SEM analysis, are shown in Fig. 3. The SEM images show that the size of the particles in the iron sludge was smaller than that of the particles in the aluminum sludge. Since the particle size is small, the area occupied by the flocs is larger, and this increases the possibility of pollutants being attached to the flocs. This is also match with [30], which the authors observed that iron electrodes were more successful than aluminum electrodes in terms of durability and cost.

In order to determine the effect of current density, the application of six different current densities (30, 40, 50, 60, 70, 80 mA cm-2) were operated in 240 min Fig. 4 shows the COD removal efficiency during the treatment with variation of current densities. At the final operation, the increment of current density from 30 to 80 mA cm-2 resulted in increment of COD removal efficiency from 72.86% to 88.25%. This can be explained by as the current density increase, the efficiency of ion production in anode and cathode also increase, leading to the percentage of removal for COD to increase. In this process, coagulant Fe3+ was produced in situ by electrochemically sacrificing of iron anode and the dosage was determined by charge loading.

PAC as a coagulant-aid was used in this study in order to enhance the removal efficiency. Fig. 5 shows the COD removal efficiency of POME in 240 min by different coagulant-aid dosages. The figure shows that a higher COD removal efficiency was achieved when the electro-coagulation process was conducted simultaneously with coagulant-aid. Furthermore, it was observed that the formation of flocs when coagulant-aid was added enhanced their surface area which at the same time increase their settling ability. Additional coagulants can change the properties of pollutant's surface charge to endorse agglomeration and enmeshment of fine particles to become larger flocs which can be easily removed by sedimentation or filtration.

Water Resources and Industry 17 (2017) 7-10

Time, min

Fig. 4. The variation of final COD removal efficiency for different current densities. EM = Iron, [PAC] =0 gL-1 and [H2O2] =0%.

0 30 60 90 120 150 180 210 240

Time, min

Fig. 5. The variation of final COD concentrations for different concentrations. EM=Iron, i=40 mA cm-2.

An amount of H2O2 as oxidizing agent was added in the electrolysis of POME for electro-Fenton system and produce hydroxyl radical (•OH) generated by H2O2 reduction (Eq.(5)) with ferrous ion (Fe2+) produced via iron oxidation at the anode (Eq.(2)).

H2O2 + Fe2+ ^ •OH + OH- + Fe3+ (9)

Hydroxyl radical (•OH) has strong oxidizing potential and has ability to oxidize organic pollutants. Thus, in order to increase COD removal efficiency, this feature was used to assist electrocoagulation process by adding1% and 2% of H2O2. Fig. 6 shows the removal efficiency of COD versus time at different H2O2 concentrations.

Fig. 6. The variation of final COD concentrations for different concentrations of H2O2 and PAC. EM = Iron, i=40 mA cm-2.

Removal efficiencies of 75.08, 80.48, 84.92% for 0, 1, 2% H2O2, respectively were obtained after 240 min of electrolysis. Moreover, 95.08% COD removal efficiency was achieved by adding 2% H2O2 plus 3 g L-1 PAC to the electrocoagulation process. Therefore, the results show that the presence of coagulant-aid and oxidant together with electrocoagulation is very effective for treating this type of wastewater.

4. Conclusion

Through investigation has been carried out in this study, electro-coagulation using iron electrode rather than aluminum is a feasible process for treatment of POME due to better removal efficiency. Treatment efficiency seen to increase with an increase in current density. The best current density for this process was recorded at 80 mA cm-2. The highest removal efficiency have been obtained in electrocoagulation process by adding 2% H2O2+3 g L-1 PAC. Indeed, the reported results showed that electrocoagulation process is more effective and significant with presence of H2O2 as oxidation agent and PAC as additional coagulant.

Acknowledgement

We gratefully acknowledge the research grant from Universiti Malaysia Pahang fund (Project Vot no. GRS 130322) for financially supporting this study. Not to forget our beloved corresponding author for support and encourage us during the study.

References

[1] Y. Zhang, L. Yan, X. Qiao, L. Chi, X. Niu, Z. Mei, Z. Zhang, Integration of biological method and membrane technology in treating palm oil mill effluent, J. Environ. Sci. 20 (2008) 558-564.

[2] A.L. Ahmad, S. Ismail, S. Bhatia, Membrane treatment for palm oil mill effluent: Effect of trans membrane pressure and crossflow velocity, Desalination 179 (2005) 245-255.

[3] a.L. Ahmad, M.F. Chong, S. Bhatia, A comparative study on the membrane based palm oil mill effluent (POME) treatment plant, J. Hazard. Mater. 171 (2009) 166-174.

[4] A.N. Ma, Y. Tajima, M. Hannif, A. and J, A novel treatment process for palm oil mill

effluent, Palm Oil res Instit Malaysia Occas, Pap 19 (1996) 201-212.

[5] L. Singh, M.F. Siddiqui, A. Ahmad, M.H.A. Rahim, M. Sakinah, Z.A. Wahid, Application of polyethylene glycol immobilized Clostridium sp. LS2 for continuous hydrogen production from palm oil mill effluent in upflow anaerobic sludge blanket reactor, Biochem. Eng. J. 70 (2013) 158-165.

[6] K. Vijayaraghavan, D. Ahmad, Biohydrogen generation from palm oil mill effluent using anaerobic contact filter, Int. J. Hydrog. Energy 31 (2006) 1284-1291.

[7] S. Yacob, Y. Shirai, M.A. Hassan, M. Wakisaka, S. Subash, Start-up operation of semicommercial closed anaerobic digester for palm oil mill effluent treatment, Process Biochem. 41 (2006) 962-964.

[8] Y. Zhang, L. Yan, L. Chi, X. Long, Z. Mei, Z. Zhang, Startup and operation of anaerobic reactor treating palm oil mill effluent, J. Environ. Sci. 20 (2008) 658-663.

[9] K. Vijayaraghavan, D. Ahmad, M.E. Abdul Aziz, Aerobic treatment of palm oil mill effluent, J. Environ. Manag. 82 (2007) 24-31.

[10] R. Del Pozo, V. Diez, Organic matter removal in cobined anaerobic-aerobic fixed-film bioreactors, Water Res. 37 (2003) 3561-3568.

[11] A.A.L. Zinatizadeh, A.R. Mohamed, M.D. Mashitah, A.Z. Abdullah, I.M. Hasnain, Optimization of pre-treated palm oil mill effluent digestion in an up-flow anaerobic sludge fixed film bioreactor: a comparative study, Biochem. Eng. J. 35 (2007) 226-237.

[12] A.L. Ahmad, S. Sumathi, B.H. Hameed, Coagulation of residue oil and suspended solid inpalm oil mill effluent by chitosan, alum and PAC, Chem. Eng. J. 118 (2006) 99-105.

[13] A. Fakhru'l-Razi, M.J. Noor, Treatment of palm oil mill effluent (POME) with the membrane anaerobic system (MAS), Water Sci. Technol. 39 (1999) 159-163.

[14] A.A.L. Zinatizadeh, B. Salamatinia, S.L. Zinatizadeh, A.R. Mohamed, I.M. Hasnain, Palm oil mill effluent digestion in an up-flow anaerobic sludge fixed film bioreactor, Int. J. Environ. Res. 1 (2007) 264-271.

[15] L. Singh, Z. a. Wahid, M.F. Siddiqui, A. Ahmad, M.H. Ab. Rahim, M. Sakinah, Application of immobilized upflow anaerobic sludge blanket reactor using Clostridium LS2 for enhanced biohydrogen production and treatment efficiency of palm oil mill effluent, Int. J. Hydrog. Energy 38 (2013) 2221-2229.

[16] A.L. Ahmad, S. Sumathi, B.H. Hameed, Residual oil and suspended solid removal using natural adsorbents chitosan, bentonite and activated carbon: a comparative study, Chem. Eng. J. 108 (2005) 179-185.

[17] M. Nasrullah, L. Singh, Z.A. Wahid, Treatment of sewage by electrocoagulation and the effect of high current density, Energy Environ. Eng. J. 1 (2012) 27-31.

[18] M. Kobya, E. Demirbas, O.T. Can, M. Bayramoglu, Treatment of levafix orange textile dye solution by electrocoagulation, J. Hazard. Mater. 132 (2006) 183-188.

[19] B. Merzouk, B. Gourich, a. Sekki, K. Madani, C. Vial, M. Barkaoui, Studies on the decolorization of textile dye wastewater by continuous electrocoagulation process, Chem. Eng. J. 149 (2009) 207-214.

[20] N. Daneshvar, a. Oladegaragoze, N. Djafarzadeh, Decolorization of basic dye solutions by electrocoagulation: an investigation of the effect of operational parameters, J. Hazard. Mater. 129 (2006) 116-122.

[21] C. Phalakornkule, S. Polgumhang, W. Tongdaung, Performance of an electrocoa-gulation process in treating direct dye: batch and continuous upflow processes, World Acad. Sci. Eng. Technol. 3 (2009) 267-272.

[22] W. Balla, a.H. Essadki, B. Gourich, a. Dassaa, H. Chenik, M. Azzi, Electrocoagulation/electroflotation of reactive, disperse and mixture dyes in an external-loop airlift reactor, J. Hazard. Mater. 184 (2010) 710-716.

[23] A. Gurses, M. Yal^in, C. Dogar, Electrocoagulation of some reactive dyes: a statistical investigation of some electrochemical variables, Waste Manag. 22 (2002) 491-499.

[24] B. Merzouk, B. Gourich, K. Madani, C. Vial, a. Sekki, Removal of a disperse red dye from synthetic wastewater by chemical coagulation and continuous electrocoagu-lation. A comparative study, Desalination 272 (2011) 246-253.

[25] F. Jing-wei, S.U.N. Ya-bing, Z. Zheng, Z. Ji-biao, L.I. Shu, T. Yuan-chun, Treatment of tannery wastewater by electrocoagulation, J. Environ. Sci. 19 (2007) 1409-1415.

[26] F. Hanafi, O. Assobhei, M. Mountadar, Detoxification and discoloration of Moroccan olive mill wastewater by electrocoagulation, J. Hazard. Mater. 174 (2010) 807-812.

[27] M. Zaied, N. Bellakhal, Electrocoagulation treatment of black liquor from paper industry, J. Hazard. Mater. 163 (2009) 995-1000.

[28] R. Katal, H. Pahlavanzadeh, Influence of different combinations of aluminum and iron electrode on electrocoagulation efficiency: application to the treatment of paper mill wastewater, Desalination 265 (2011) 199-205.

[29] M. Ugurlu, a. Gurses, C. Dogar, M. Yal^in, The removal of lignin and phenol from paper mill effluents by electrocoagulation, J. Environ. Manag. 87 (2008) 420-428.

[30] H.A.C. Moreno, D.L. Cocke, J.A.G. Gomes, P. Morkovsky, J.R. Parga, E. Peterson, C. Garcia, Electrochemical reactions for electrocoagulation using iron electrodes, Ind. Eng. Chem. Res. 48 (2009) 2275-2282.