Surfactin foams: Uniform and Steady State in Foam-Generator

  ================================================================================================ Fakultas Teknik UISU Kampus AI Munawarah JI. SM. Raja Teladan Medan

  Seminar Naslonal Teknologl & Rekayasa ISBN 978-979-19778-0-7

  

Surfactin foams: Uniform and Steady State in Foam-Generator

• a*

  Bode Haryanto ,

G. Aryo Wicaksono Jo-Shu Chang

  Chemical Engineering Department, Department of Chemical Engineering, National Department of Chemical University of Sumatra Utara, Cheng Kung University, Tainan 701, Taiwan Engineering, National Cheng Kung

  Medan, Indonesia University, Tainan 701, Taiwan haryanto_bode@yahoo.com

  

Chien-Hsiang Chang*

  Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan changch@mail.ncku.edu.tw

  

Abstract

This Study was initiated by generating foams from biosurfactant surfactin in a foam-generator which then used to remediate

contaminated soil in column by flushing technology. Focus of this paper was to evaluate the dynamic performance of surfactin

foam generation, in particular reaching the uniform and steady state condition in the foam-generator. The condition was

recorded by observing the level of liquid-height phase as a function of time. The experimental results demonstrated that for

surfactin at concentrations of 1 cmc (critical micelle concentration) and 3 cmc with the same flow rate (2 ml/min), a uniform

and steady state condition was reached after 20 minutes. Increasing the concentration from 1 cmc to 3cmc, one could increase

the foam capacity about 12.5%. By changing the flow rate from 2 ml/min to 3 ml/min for surfactin with a concentration of 3cmc,

it was found that the time scale to reach the uniform and steady state became shorter, but with a slight decrease in the foam

capacity. In addition, the steady condition seemed uncharged when the foam was flowed into the flushing remediation column.

  Keyword: surfactin, foam-generator, foam-capacity.

1. Introduction

  Surfactin was discovered about 40 years ago, there has been a revival of interest in this compound over the past two decade, triggered by an increasing demand for effective biosurfactants for difficult contemporary ecological problems. Surfactin, a biologically active compound produced by various strains of Bacillus subtilis (Regina and Ptak, 1992; Ishigami et al, 1995; Kowall et al., 1998; Peypoux et al., 1999, Yeh, et al., 2005). Surfactin reported has an anionic lipopeptide biosurfactant with two negative charges; having critical micelle concentration (cmc)

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• 1

  of 9, 410 M (about 10 ppm) and surface tension (γ ) at cmc of 30 mNm in 0, 1 M NaHCO (pH 8.7) (Ishigami et al. 1995). Surfactin is cyclic

  cmc

  3

  peptides containing a β-hydroxy fatty acid. Surfactin has micelle weight = 179 000 with aggregation number N—173; micelle length 115.5 nm; diameter 5.6 nm and has rod micelle structure (Ishigami et al, 1995). Surfactin with its biodegradability, low toxicity, and effectiveness in enhancing biodegradation and solubility of hydrophobic compounds, have excellent ability as surfactant. The ability of surfactin have been reported by Ishigami et al. 1995; Razafindralambo et al. 1996; Kowall et al. 1998; Peypoux et al. 1999; Mulligan et al. 1999; Hwang et al. 2007.

  Foam is an emulsion-like two-phase system where the mass of gas or air cells is dispersed in a liquid and separated by thin liquid films called lamellae. Two important characteristics of foams are quality and stability (Razafindralambo et al., 1996; Chowdiah et al., 1998; Mulligan and Eftekhari, 2003). ======================================================================================================== Fakultas Teknik UISU Kampus AI Munawarah JI. SM. Raja Teladan Medan Seminar Naslonal Teknologl & Rekayasa ISBN 978-979-19778-0-7 Foam stability reflects the ability of the foam to resist bubble collapse. It can be quantified by the time required for collapsing half of the foam. The overall question of foam stability requires the consideration of both the static and dynamic aspects of bubble interactions (Wang and Mulligan, 2004). Razafindralambo et al. (1998) reported that foaming property could characterize by various parameters including foaming capacity (FC):

  (1) Rothmel et al. (1998) concluded that foam stability does not appear to be dependent upon inherent properties such as hydrophile–liphophile balance and cmc. A major goal of foam research is development of a fully mechanistic and predictive foam simulator (Rossen, 2003). The foam capacity in the foam generator has certain volume at steady state. It has relatively varying for different concentration and operation condition for each surfactant.

  Various remediation techniques have been developed, among them, the washing processes with surfactants and biosurfactants are the most used. Washing with foam enhanced technique can be developed to increase efficiency in soil flushing remediation technology. Foam enhanced can improve the ability to control the migration of contaminant laden fluids (Huang and Chang, 2000; Wang and Mulligan, 2004; Mulligan and Wang, 2006). The presence of foam has a profound effect on the mobility of fluid phases flowing in a porous medium. This improves the mobility ratio and thus the homogeneity of the flood (Chowdiah et al., 1998; Huang and Chang, 2000; Wang and Mulligan, 2004). Furthermore, foam was also found to hold promise for improving sweep efficiency in oil recovery processes (Wang and Mulligan, 2004). Apparently, the efficiency of foam-enhanced surfactant solution (flooding volume/ pressure), depends upon the surfactant type, the surfactant concentration, and the ratio of gas to liquid in the foam injected (Chowdiah et al., 1998; Mulligan and Eftekhari, 2003; Wang and Mulligan, 2004; Mulligan and Wang, 2006).

  The foam generation should have reached a uniform and steady state before flowing out to column remediation (Mulligan and Wang, 2006). This condition should have be the starting time to flow into column remediation. It is an important step in flushing system with foam enhanced technique. The foam generating usually reached uniform and steady state, depends upon flow rate of surfactant concentration and gas or air into foam-generator (Huang and Chang, 2000; Wang and Mulligan, 2004; Mulligan and Wang, 2006). In this study, experiments were performed to reach foam stabilization (uniform and steady state) of biosurfactant surfactin in foam- generator (foam enhance technique) to be used in flushing remediation system. The uniform and steady state indicator was predicted from the level of the liquid phase height of surfactant in the foam-generator.

2. Material and Methods

2.1. Biosurfactant Fig.1 The HPLC analysis suggested the surfactin purity was about 85%.

  ====================================================================================================== Fakultas Teknik UISU Kampus AI Munawarah JI. SM. Raja Teladan Medan

  20 Seminar Naslonal Teknologl & Rekayasa ISBN 978-979-19778-0-7 Surfactin was used as surfactant. The surfactin was produced in Energy/Environmental Biotechnology and biochemical Engineering Laboratory, Chemical Engineering Department, NCKU. Bacillus subtilis ATCC 21332 is used to produce a lipopeptide type

  o

  biosurfactant, surfactin. Surfactin is purified until 85% purity and keep in the deep refrigerator with temperature – 80 C (Yeh et al, 2005). Figure 1 below shows HPLC chromatogram with the retention time indicates of six kinds of surfactin as known.

2.2. Foam generator

  This study applied foam enhanced flushing column remediation with foam-generator. The foam-generator designed and made by laboratory of interfacial technology, chemical engineering department NCKU. A glass column of foam-generator (L= 10,5 cm, OD=3.5 cm), equipped with circular porous, which enabled the foam generation in the presence of surfactant solution and nitrogen gas as shown in the figure 2 below.

  2.3. Experimental set up and Procedures This study was a series of preliminary experiments, conducted to investigate different parameters involved in the biosurfactant foam technology in soil remediation. All experiments were conducted at room temperature (25.0°C) and at pH 8. Surfactin solutions were prepared in

• 3
• 5 -5

  10 M Tris buffer (pH 8.0) using MilliQ Plus water (Millipore Co.) with concentration over the surfactin cmc such as, 2 10 M (1 cmc) and6 10 M (3 cmc).

  Surfactin solution flow rate was fixed at 2 and 3 ml/min. A peristaltic pump was used to feed the surfactant solution to foam-generator column. Two flow meters were used to control the flow of the solution and the gas before entering the foam-generator column. In each experiment, 200 ml surfactin solution was used with running time 50 minutes. Each experiment was done in three times. Nitrogen gas flow rate was fixed at 20 cc/min. The samples of the generated foam were recorded by measuring the height of liquid phase in the foam generator. Dynamic level of liquid height phase was recorded as function of time. Recording (t =0) was started when the surfactant flow into foam-generator at certain height level and then the gas was flowed into foam generator. The recording was finished when the height of liquid in the foam-generator was stable. Dynamic level of liquid height phase was recorded after steady state to flow into column remediation. Column remediation was filled by glass beads that has contaminated by oil 0.9457g.

  Fig.2 A design of flushing column remediation system with the foam-enhanced technique.

3. Result and Discussion

  Studies were performed on the different flow rates and concentrations of surfactin solutions pumped into foam-generator. It’s to determine the foam capacity to reach a uniform and steady state in the foam-generator before flowing out to column remediation. The experimental results showed that the foam generation rate has reached a uniform and steady; tend not much different for surfactin concentration 1cmc and 3cmc with the same flow rate 2 ml/min. The different starting volume of surfactin solution in the foam generator, found that the time to reach uniform steady state has little different as shown figure 3a below. The foam generating was almost linear fashion after 20 min for each concentration. The dynamic level of liquid height have been calculated and the foam height in foam-generator was about 3.5 and 4 cm from the top. It was calculated that the increasing concentration of surfactin, increased the volume of foam generation (foam capacity) 12.5%. ======================================================================================================== Seminar Naslonal Teknologl & Rekayasa ISBN 978-979-19778-0-7 It was shown that at lower concentration provide a little faster to reach steady state as shown in picture 3(a) below. It was reported that by increasing the surfactin concentration, mostly increases the foam capacity but not to their stability (C-L Hu, 2008).The experimental results showed for surfactin concentration 3cmc M that the dynamic levels of liquid height phase was different for different surfactin flow rate. The foam generation rate has reached a uniform and steady state after about 10 minutes at flow rate 3 ml/min as shown in picture 3 (b) below. It was shown that by increasing the flow rate of surfactin from 2 ml/min and 3 ml/min could decrease one and half times to reach steady state. Other hand, it decreased a bit the foam capacity in column. _{9.8 9.6}

  9.4 _9.4

  9.2 _9.2

  9.0 ) ) _9.0

  8.8 cm cm t ( t ( _8.8

  8.6 gh gh ei ei _8.6 h h

  8.4 Liquid flow rate : 2 ml/min id flow rate 3 ml/min id _8.4 Gas flow rate : 20 cc/min flow rate 2ml/min qu qu

  8.2 Li Li _{8.2 Liquid height for 6.10-5 M Liquid height for 2.10-5 M 8.0}

  8.0 Surfactin conc.: 6 x 10-5 M _{7.6 7.8}

  7.8 _{10 20 30 40 50}

  7.6

  10

  20

  30

  40

  50 Time (minutes) Time (minutes) Fig.3. (a) Dynamic level of liquid phase height as a function of time and (b) the effect of different surfactin flow rate on the liquid height.

  The uniform and steady state of foam capacity during flowing to the column remediation, to remove oil from sand was shown on figure 4 below. Liquid height was constant when remediation proceeded. It’s shown that the pressure jump down (drop) or up was not significant in this condition. Concerning the stability of flushing system in column remediation using glass bead, might be different if using soil or sand. Moreover, the results show that the liquid height with different cmc relatively keep the foam capacity in the foam generator was constant. The foam capacity in column with different surfactin concentration 1cmc and 3cmc were shown in stable condition. _{9.5 9.6}

  9.4 )

_{Liquid flow rate : 2 ml/min}

cm t ( Gas flow rate : 20 cc/min _9.3 gh ei h _9.2 concentration 2.10--5 M (I) id -5 concentration 6.10 M (II) qu Li _{8.9 9.0 9.1 2 4 6 8 10} Remediation time (minutes) Fig.4. Steady state condition after flowing into the remediation column for liquids with different concentrations.

  This condition usually proposes as initial moment to measure the ability of one surfactant to absorb heavy metal and/or remove oil from contaminated sandy soil (Huang and Chang, 2000; Wang and Mulligan, 2004; Mulligan and Wang, 2006). The experimental results showed that the foam generation rate has reached a uniform and steady state relatively independent to surfactin concentration. Increasing the concentration will increase the foam capacity in foam-generator. Increasing the flow rate of surfactin solution relatively improves the time to reach steady state condition but decreased a bit the foam generation. ======================================================================================================== Fakultas Teknik UISU Kampus AI Munawarah JI. SM. Raja Teladan Medan Seminar Naslonal Teknologl & Rekayasa ISBN 978-979-19778-0-7

  4. Conclusion This study investigated the surfactin foam generation behavior in a foam-generator. Reaching foam uniformity and steady state is an important step in the flushing remediation system with the foam-enhanced technique. The experimental results showed that for the foam generation rate to reach a uniform and steady state, it was almost independent to the surfactin concentration. Increasing the surfactin concentration, one could increase the foam capacity in the foam-generator. The higher flow rate of a surfactin solution would shorten the time to reach the steady state condition but slightly decrease the foam capacity as reported by Chowdiah et al. (1998), Mulligan and Eftekhari (2003), Wang and Mulligan (2004) and Mulligan and Wang (2006). This paper reported that it is important to consider the foam capacity in the foam-generator column to have a shorter time to reach steady condition for increasing the operational efficiency.

  5. References [1] Peypoux F., Bonmatin M., Wallach J., Recent trends in the biochemistry of surfactin, Appl Microbiol Biotechnol 51, 1999. 553-563 [2] Yutaka. I, Osman M., Nakahara H., Sano Y., Ryo I., Mutsuo M., Significance of r-sheet formation for micellization and surface adsorption of surfactin, Colloids and Surfaces B: Biointerfaces 4, 1995. 341-348 [3] Liang-Ming W., Pao-Wen G., Chih-Chung M., Sheng-Shung C., Application of biosurfactants, rhamnolipid, and surfactin, for enhanced biodegradation of diesel-contaminated water and soil, Journal of Hazardous Materials 15, 2008. 155–163 [4] Mulligan C. N., Wang S., Remediation of a heavy metal-contaminated soil by a rhamnolipid foam, Engineering Geology 85, 2006. 75–81. [5] Huang C.W, Chang C.H, A laboratory study on foam-enhanced surfactant solution flooding in removing n-pentadecane from contaminated columns, A: Physicochemical and Engineering Aspects 173, 2000. 171–179 [6] Suiling W., Mulligan C. N., An evaluation of surfactant foam technology in remediation of contaminated soil, Chemosphere 57,

  2004.1079–1089 [7] Chowdiah P., Misra B.R, Kilbane J., Srivastava V.J., Hayes T.D., Foam propagation through soils for enhanced in-situ remediation,

  Journal of Hazardous Materials 62, 1998. 265–280 [8] Yeh M. S., Wei Y.H., and Chang J.S., Enhanced Production of Surfactin from Bacillus subtilis by Addition of Solid Carriers, Biotechnol. Prog. 21, 2005.1329-1334

  [9] Mulligan C. N., Raymond N. Y., Bernard F. G. , Susan J. , Bennett H. P. J., Metal Removal from Contaminated Soil and Sediments by the Biosurfactant Surfactin, Environ. Sci. Technol. 33, 1999. 3812-3820 [10] Mulligan C. N., Farzad E., Remediation with surfactant foam of PCP-contaminated soil Engineering Geology 70, 2003. 269–279 [11] Rothmel, R.K., Peters, R.W., Martin, E.S., Deflaun, M.F., Surfactant foam/bioaugmentation technology for in situ treatment of TCE-DNAPLs. Environ. Sci. Technol. 32, 1998. 1667–1675. [12] Santanu P., Surfactant-enhanced remediation of organic contaminated soil and water, Advances in Colloid and Interface Science 138,

  2008. 24–58 [13] Razafindralambo H., Paquot M., Baniel A., Popineau Y., Hbid C., Jacques P., Thonart P., Foaming Properties of Surfactin, a

  Lipopeptide Biosurfactan from Bacillus Subtilis, JAOCS 73, No.1, 1996.149-150 (Short Communications) [14] Razafindralambo H., Popineau Y., Deleu M., Hbid C., Jacques P., Thonart P., Paquot M., Foaming Properties of Lipopeptides Produced by Bacillus subtilis: Effect of Lipid and Peptide Structural Attributes , Journal Agric. Food Chem. 46, 1998. 911 – 916.

  [15] Chih-Lin Hu, An investigation on the applications of surfactin to soil remediation, Master Thesis, Chem. Eng. NCKU, 2008.

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