E-Jurnal Ilmu dan Teknologi Kelautan Tropis, Vol. 2, No. 1, Hal. 1-8, Juni 2010
STUDY ON BIOROCK® TECHNIQUE USING THREE DIFFERENT ANODE MATERIALS (MAGNESIUM, ALUMINUM, AND TITANIUM)
1*) 1 1 Neviaty P. ZamaniP P, Ramadian BachtiarP P, Hawis H. MadduppaP P, Jhoni Wahyu 2 1 1 1 AdiP P, Jeddah IsnulP P, Muhamad IqbalP P, and Beginer SubhanP
1. Department of Marine Science and Technology, Faculty of Fisheries and Marine Science, Bogor Agricultural University, Jl. Agatis No.1, Bogor 16680, Indonesia 2. Department of Metallurgy and Materials, Faculty of Mathematics and Science, University of Indonesia, Depok 16424, Indonesia *) P PE-mail: 1TU [email protected]
ABSTRACT Biorock® technique is the earliest methods to rehabilitate the damage of coral reef ecosystem. Its improvement is need to carry on since it is subject to some inhibitions in particular the dependence of expensively-imported Titanium (Ti) as the anode materials. The main purpose of this research was to find the best anode material as a possible subtitution which can be economically and easily to apply in Indonesia. Therefore we compared Titanium (Ti) with two other potential anodes material (Magnesium-Mg, and Aluminum (Al). The laboratory study was carried out for two days period (48 hours) in the stagnant sea water aquaria. Four aquarium tanks were treated by different electric current treatment (1 Ampere, 2 Ampere, 3 Ampere, and 5 Ampere, respectively). The reduction of electrode weigh (anode and cathode) was measured. During the experiment, water quality (i.e. pH, and salinity) and mineral waters (calcium) were collected every 6 hour in 48 hours. The solid form of calcium carbonate was analyzed using XDS (X-ray Dispersion Spectrophotometer). The accretion rates on cathode and anode decay were compared between anodes which were treated by different electrical current. Based on the study, three anodes (aluminum, magnesium and titanium) showed different respond. Titanium and Magnesium anode showed electric current affected accretion rate (P < 1), while for aluminum anode showed no differences on treatments.
Keywords: mineral accretion, Biorock®, anode, coral reef rehabilitation, accretion rate, anode decay rate, mineral uptake
I. INTRODUCTION the composition of natural coral reefs (Lee, 2002). This solid mineral is a Biorock® is using mineral byproduct of pH changes in the cathode accretion process and one of coral reef during the electrolysis process of sea rehabilitation methods since late 1990s in water (Hilbertz and Goreau, 1996). This Indonesia, which developed by Thomas method is furthermore increase coral reef Goreau, a marine biologist and Wolf growth 3-5 times faster than the normal Hilbertz, an engineer and architect conditions (Lee, 2002). The associations (Hilbertz, 1979 and 1991; Bachtiar, between organisms in that structure is 2003). Mineral accretion process is faster and more diverse for certain case applying a low voltage direct electrical and even can be ten times faster current through electrodes causing (Faraday, 2004). mineral crystals naturally found in Anode material is one of the most seawater, mainly calcium carbonate and important parts to apply Biorock® magnesium hydroxide, to grow on the structure. Anode defined as the electrode structure (Hilbertz, 1979; Hartt 1984). where the electrons come from the cell The composite of limestone and brucite and oxidation occurs (Hastatiningsih, which found on the structure is similar to 1997). Anode connected to the positive
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terminal of power supply and a terminal 2.2. Experiment set-up where electrons taken from the ions in solution to facilitate chemical reactions. Cathode and anode was set on If the current is too high, the anode will rounded wooden skeleton like a rack with corrode quickly (Hilbertz and Goreau, space for cathode and anode on it. Anode 1996). Anode material used in Biorock® was set on the center, and cathodes were structure should have high resistance to set surround the anode with the same corrosion processes and have a high level interval (Figure 2, left). of polarity due to the occurrence of Each cathode wire was combined oxidation reactions. In addition, pH and connected to negative terminal of values around the anode are acidic, which power supply, and anode wire was is potential to generate corrosion at iron, connected to positive terminal of power as cathode. supply. Each wire was shield by tape. Titanium used as anode for the The electric current’s setting and structure since its application (Lee, measuring was conducted after all 2002). However, its improvement is devices submerged in the aquarium filled needed to carry on since it is subject to with sea water (Figure 2, right). some inhibitions in particular the dependence of expensively-imported Titanium (Ti) as the anode materials in Indonesia. The main purpose of this research was to find the best anode material as a possible substitution which can be economically and easily to apply in Indonesia. Therefore we investigated the feasibility of Titanium (Ti) with two other potential anodes material (Magnesium-Mg, and Aluminum-Al), and treated in a different current density (1 Ampere, 2 Ampere, 3 Ampere, and 5 Ampere). Figure 1. Anode materials used for the Biorock experiment (left: II. METHOD Aluminum, middle: Magne- sium, right: Titanium) 2.1. Preparation 2.3. Observation and data collection The preparations of the research are the following steps: (1) The iron stick The research was carried out for 3 was burnished in order to clearance the months period (January to March 2006) rust; (2) anode materials preparations and at the Laboratory of Marine Biology, productions (Figure 1); (2) Wire setting Department of Marine Science and on two electrodes (cathode and anode); Technology, Bogor Agricultural (3) Tip of the cathode was rubbed with University. The experiment was carried Resin in order to avoid corrode and the out for two days (48 hours) in four two edge of iron stick would not be aquariums, which filled with sea water covered by CaCO R3 Rdeposit; (4) Electrode and no current. Each aquarium was numbering; and (5) Electrode weighing. applied in different electric current (1
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Ampere, 2 Ampere, 3 Ampere, and 5 further analysis. Sample analysis using Ampere). Data was collected every 12 AAS was conducted in Environment hours start from tR0R (starting time) with no Laboratory of Bogor Agricultural repetition. pH values were measured University. during the experiment. Mineral solid form as accretion Sample of sea water in the aquaria product was collected as dry material was collected to monitor the composition after 12 hours and weighted. Sample of of Ca and Mg during the experiment. mineral solid was collected for further Water sample were put in the glass bottle mineral analysis in Metallurgy and three drops of HNOR3R added as sea Laboratory-University of Indonesia by water preservation. Then glass bottle using XDS (X-ray Dispersion sample was wrapped by aluminum foil Spectrophotometer). paper and kept in room temperature for
Figure 2. Schematic of electrode setting on wooden skeleton (left); and experiment set- up system in four identical aquariums which treated different electrical current from power supply (right).
2.4. Statistical analysis current. This is can be found on 3 Amp and 5 Amp, while on 1 Amp and 2 Amp Mineral solid weight and decay rate was slower in changes. were calculated based on the value before Sea water pH in the aquarium had a and after experiment in the cathode and significant change. At the titanium and the anode, respectively. The mineral solid aluminum anode, pH had decreased from weight formed and anode decay rate about 8 to 6. However, the magnesium parameters were compared using anode pH had tends to increased, ranged Randomized Complete Block Design, from 8.1 to 8.9 (Figure 3). continued with ANOVA (Analysis of pH decreasing which occurred in Variant) and Least Significance titanium and aluminum anode because + Difference using Statistica 7 (Ashworth the concentration of increasing [HP P] and and Booker, 1986). the formation of acid. This was come from derived carbonic acid fraction and III. RESULTS AND DISCUSSION the reaction at the anode. In the ocean occurs carbonate system which 3.1. pH variability maintaining the pH of sea water in the buffer conditions. However, in a closed Changes of pH value rapidly occur and limited system (e.g. aquarium), in experiment treated large electrical buffer conditions would not happen.
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Therefore, there is a change of pH 3.2. Calcium and Magnesium uptake seawater. Changes in pH are the result of the Ca and Mg uptake value generally occurrence of electrolysis reaction at the showed decreased on each anode electrode (cathode and anode). Reaction (Titanium, aluminum, and Magnesium) at the cathode was reduction and an during observation period (Figure 4 and - alkaline, because of release [OHP P]. As for Figure 5). The rising values of Ca uptake what happened in the anode were the were on 3 Ampere at Aluminum anode, 1 oxidation reaction and an acid because it Amp Magnesium anode and of Mg + releases [HP P]. Consequently, more acidic uptake was on 1 Amp Magnesium anode. conditions predominate in the aquarium. Decreased value of Ca and Mg were caused by this materials were used in
10 mineral accretion process. 2T It applies an
8 electric charge, causing dissolved
1 Ampere 6 minerals (Mg and Ca) to crystallize on 2 Ampere 3 Ampere the iron stick (cathode). 2TCa uptake on
pH value pH 4 5 Ampere titanium anode ranged between 500 – 2 800 mg/L and Mg uptake ranged between 0 0 12 24 36 48 140 – 160 mg/L. Observation periods (hours) 3.3. Mineral element composition 10 8 Magnesium hydroxide and 1 Ampere 6 2 Ampere calcium carbonate are one of the main 3 Ampere
pH value pH 4 5 Ampere components of Biorock®. This 2 composition is essentially the result of 0 the ionic composition of seawater. 0 12 24 36 48 Observation periods (hours) Comparison between mineral compositions, Magnesium (Mg) and 10 Calcium (Ca), which crystallized on the 8 cathode, is shown on Figure 6. In 1 Ampere 6 2 Ampere general, Mg composition much more 3 Ampere
pH value pH 4 5 Ampere dominant than Ca on each anode samples
2 (titanium and magnesium). This is
0 similar to reef composition. Reef as a 0 12 24 36 48 control for the experiment showed ratio Observation periods (hours) between Mg and Ca is 2:1. Ratio of Mg:Ca which closer to reef composition Figure 3. pH variability in the aquaria is on titanium with 1A (2:1). As on with Titanium anode (above), titanium with 2A dan 3A is 5:1 and 6:1, Aluminum anode (middle), and respectively. On Magnesium anode Magnesium anode (below), showed ratio with 1A, 2A and 3A is 4:1, treated on four different 9:1 and 33:1, respectively. electric current (1, 2, 3 and 5 Ampere).
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1000 160
800 155 1 A mpere 1 Ampere 600 2 A mpere 2 Ampere 150 3 A mpere 3 Ampere 400 5 A mpere 5 Ampere Ca uptake (mg/L) uptake Ca Mg uptake (mg/L) uptake Mg 145 200
0 140 0 12 24 36 48 0 12 24 36 48 Observation period (hours) Observation period (hours)
1000
800 Figure 5. Magnesium (Mg) uptake on 1 A mpere 600 two different anodes (above: 2 A mpere 3 A mpere Titanium, below: Magnesium) 400 5 A mpere Ca uptake (mg/L) uptake Ca in different electric current (1, 200 2, 3, and 5 Ampere) during 48 0 0 12 24 36 48 hours observation period. Observation period (hours)
45 Mg 1000 40 35 Ca 800 30 1 A mpere 25 600 20 2 A mpere 15 3 A mpere 400 10 5 A mpere Ca uptake (mg/L) uptake Ca Element composition (%) composition Element 5 200 0 1A 2A 3A 1A 2A 3A 0 Reefs Titanium Magnesium 0 12 24 36 48 reefs and anodes Observation period (hours)
Figure 6. Element composition of Figure 4. Calcium (Ca) uptake on three Magnesium (Mg) and different anodes (above: Calcium (Ca) at two anodes Titanium, middle: Alumi- (Titanium and Magnesium) nium, below: Magnesium) in in three different current different electric current treatment (1 A, 2 A, and 3 treatment (1, 2, 3, and 5 A), compared to reefs as Ampere) during 48 hours control. observation period.
Highest percent element 160 composition of Mg which formed
155 become solid (Mg(OH)R2R) compared to Ca 1 Ampere
2 Ampere R R 150 which formed become CaCO3, because 3 Ampere 5 Ampere solubility of CaCOR3R is very affected by Mg uptake (mg/L) uptake Mg 145 the carbonate system in the sea water
140 (Hilbertz, 1979; Hartt 1984). The amount 0 12 24 36 48 Observation period (hours) of dissolved carbon dioxide in sea water declines with increasing temperature. 2- Hence, will reduce the amount of COR3RP P which can be dissolved in solution. Even
at a high temperature, CaCOR3R will precipitated spontaneously and will be o significantly at temperatures over 40P PC.
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The temperature on the aquarium the change in hydrogen ions into experiment ranged barely between 27-28P hydrogen gas that spurred the formation o - PC. It can be said that the level of of hydroxide ions (OHP P ), resulted from solubility of CaCOR3R decreases with the the decomposition of HR2RO compounds. increase of sea water temperature. In addition carbonic acid in sea water breaks down into hydrogen ions and 2- 3.4. Accretion and decay rate bicarbonate ions (COR3RP P), due to lack of hydrogen ions. Then the dissolved Treatment of different electrical minerals in seawater changed into solid current in each anode was resulting form CaCOR3R and Mg(OH)R2R. accretion rate and anode decay rate. The As the reaction at the anode was rate of accretion was indicated by the discard the anode increasingly due to number of solid minerals formed at the oxidation reactions. Anode material used cathode during the process of mineral should have high resistance to corrosion accretion. While the rate of decay processes and have a high level of showed how much part of anode waste polarity. A high level of polarity is away due to reduction reaction in the usually indicated by a positive value seawater. galvanometric. The more positive, the Based on current treatment material is getting stronger against the differences showed greater accretion rate corrosion process. Aluminum and along with the amount of electrical magnesium is a material with a negative current applied to each of the anode value galvanimetris and include as a fully materials. However, accretion rate on consumable metals. This material will be magnesium and titanium anode has dissolved with electric current given. For decreased in the current 5 Ampere. The every one or two atoms from the anode highest accretion rate on magnesium will break down into solution for each anode with current 3A with a value of molecule formed seament. Therefore, 5.2267 g/48 hours. While the smallest these two materials have a large decay accretion rate on titanium anode with rate (Figure 7, below). current 1 Ampere with a value of 0.6400 Titanium anode is a fully passive g/48 hours. In general, magnesium anode type anode. This anode has a conductive has a large accretion rate than the other coating on the surface electric. This two anodes (Figure 7, above). membrane is conduction and not reactive. The rate of anode decay in The only reaction that occurs from the accordance with the greater amount of anode of this type is the formation of gas electricity treated. In a drastic decay rate and the decay rate is one million times of magnesium occurs in a current of 3 lower than the fully type consumable Ampere and 5 Ampere with a value anode metals. Therefore, in the titanium 17.63 g/48 hours and 17.83 g/48 hours, anode has a very small decay rate (Figure respectively. This is the largest rate 7, below). compared with the other anodes. On Based on ANOVA, Titanium and titanium, decay rate has a very small and Magnesium anode indicated electrical not significantly (Figure 7, below). The current affects accretion rate (P<1). larger current provided will trigger a big While on Aluminum anode showed no reaction in cathode and anode. The significantly different between electrical reaction at the cathode further accelerate current treatment to accretion rate (P<1). the accretion due to the change in pH Further analysis with Least Significance value. These pH changes resulting from Difference indicated effect of electrical
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current. For all electrical current while on Titanium anode showed on 2 combination on Magnesium and Amp and 3 Amp. Generally, all anodes Titanium anode showed real effect on showed small ratio on 2 Amp. This was a accretion rate, unless on 3 Amp and 5 potential current for Biorock structure Amp. Higher current density produces (Table 1). faster mineral accretion rate, however the quality of the lime was unsatisfactory. Tabel 1. Ratio of decay rate/accretion rate on a three different anode materials
20 (Aluminium, Magnesium, and Titanium), treated with different electric current 15
Aluminum density (1, 2, 3, and 5 Ampere) 10 Magnesium Titanium g/48 hours g/48 Type of Electrical current (Ampere) 5 anode 1 2 3 5 0 1,367 1,442 1,426 2,132 1 Ampere 2 Ampere 3 A mpere 5 A mpere Aluminum 9 1 3 4 Current density (Ampere/m2) Magnesiu 2,500 1,834 3,373 3,755 20 m 0 9 5 7 0,156 0,072 0,065 0,133 15 Titanium 2 1 8 9 Aluminum 10 Magnesium Titanium g/48 hours g/48 IV. CONCLUSION 5
0 Based on the study, three anodes 1 Ampere 2 Ampere 3 A mpere 5 A mpere Current density (Ampere/m2) (aluminum, magnesium and titanium) showed different respond. Titanium showed the best result, followed by Figure 7. Accretion rate (above) and Magnesium Aluminum anode. The best anode decay rate (below) on treatment criteria are: produce the highest anode materials (Aluminum, rate of mineral accretion, hardness level Magnesium, and Titanium), of solid minerals (known from the ratio treated with different electric of Ca/Mg), lowest anode decay rate, and current density (1, 2, 3, and 5 the lowest oxide production. These Ampere). factors were combined to get the best treatment combination. 3.5. Anode material efficiency Acknowledgement The ratio of decay rate or accretion rate was used to see the efficiency of We would like to thank Thomas each material with electrical current Goreau (Global Coral Reef Alliance); treatment. Small ratio values show a Wolf Hilbertz (Sun & Sea NV); better efficiency because as low decay Laboratory of Marine Biology, rate can produce a large accretion rate. Department of Marine Science and Titanium anode showed the lowest Technology, Bogor Agricultural ratio in the experiment. This was because University; Laboratory of Metallurgy and of low decay rate and high accretion rate. Materials University of Indonesia; and Based on electrical current treatment the for all people who have contributions in small ratio at Aluminum anode showed this research. The study was funded by on 1 Amp, 2 Amp and 3 Amp; On Ministry of Research and Technology Magnesium anode showed on 2 Amp;
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Republic Indonesia, and Indonesian Critical Review. Corrosion, 40: Insitute of Science through research 609-618. program “Riset Unggulan Terpadu 2005- Hastatiningsih. 1997. Oksidasi - Reduksi 2007”. dan Elektrokimia. Bogor: Jurusan Kimia-FMIPA, Institut Pertanian References Bogor. Hilbertz, W. H. 1979. Electrodeposition Ashworth, V. and C. J. L. Booker. 1986. of Minerals in Sea Water: Cathodic Protection: Theory and Experiments and Applications. Practice. UK: Horwood Limited IEEE Journal on Oceanic Chinchester. Engineering, 4:94-113. Bachtiar, R. Pengamatan Pembentukan Hilbertz, W. H. 1991. Solar-generated Terumbu Buatan dengan Metode construction material from sea Mineral Accretion di Desa water to mitigate global warming. Pemuteran, Bali Barat. Skripsi Building Research and Sarjana, Jurusan Ilmu dan Information, 19:242-255. Teknologi Kelautan FPIK, Institut Hilbertz, W. H. and T. Goreau. 1996. Pertanian Bogor, Indonesia, 2003. Method of enhancing the growth Faraday, M. 2004. Experimental of aquatic organisms, and Researches in Electricity. Eighth structures created thereby. United Series. Philosophical States Patent Number No.5 543 Transactions of the Royal Society 034. of London, 124: 425-470. Lee, E. R. 2002. Physics of seament StatSoft, Inc. www.statsoft.com. electro accretion. Hartt. 1984. Calcareous Deposits on www.stanford.edu/ [visit on 10 Metal Surfaces in Seawater - A December 2005]
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