Synthesis Of Metal-Tannate Complexes And Their Application As Antifoulant For Fish Cage Nets
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Date
2016-04
Authors
Achmad, Azraa
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Abstract
Marine biofouling is the attachment of colonized marine organisms on surfaces that are immersed into the seawater in which its formation is influenced by several potential chemical, physical and biological processes. This biofouling significantly affect the outcome of aquaculture industry due to the fouling of the fish nets. Therefore, antifoulant is used in the formulation of antifouling paint in order to avoid the settlement of marine biofouling. Previous metal-based antifoulant like tributyltin tends to be harmful to the natural environment and has been banned by the International Maritime Organization (IMO). The main objective of this research is to find an option for more ecofriendly antifoulant by synthesizing some metal ion-tannate complexes which are natural products based antifoulants that have antifouling properties. In this study, three new antifoulants were synthesized by complexing tannin from mangrove bark of Rhizophora apiculata species with metal ions which were copper (Cu), iron (Fe) and aluminium (Al). The optimization of metal tannate complexation was studied under various conditions including the effect of metal dosage, pH, temperature and reaction time. The optimum dosage conditions for copper-tannate (Cu-T) was 1: 2 dosage ratio of Cu ion per mangrove tannin (MT) meanwhile both iron-tannate (Fe-T) and aluminium-tannate (Al-T) were 1:3 dosage ratio of ion per MT. A temperature of 60 ºC, pH 5 and 30 minutes reaction time were obtained as the optimum conditions for both Cu-T and Fe-T. Meanwhile, for Al-T complex it was at pH 4.5 with temperature of 45 ºC and 30 minutes reaction time.
The properties of this metal tannate complexes were characterized by using Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy with energy dispersive X-ray (SEM-EDX), Atomic Absorption spectroscopy (AAS), the toxicity test using brine shrimp, Artemia salina as control organism and antimicrobial test. Based on the toxicity tests, all complexes were considered toxic due to the LC50 value which is below 1.0 mg mL-1, by means followed the order from the most toxic to the least toxic: copper oxide (Cu2O) (0.018 mg mL-1) > copper-tannic acid (Cu-TA) (0.020 mg mL-1) > Cu-T (0.029 mg mL-1) > copper omadine (Cu-OM) (0.036 mg mL-1) > iron-tannic acid (Fe-TA) (0.045 mg mL-1) > aluminium-tannic acid (Al-TA) (0.053 mg mL-1) > Fe-T (0.064 mg mL-1) > Al-T (0.077 mg mL-1) > tannic acid (TA) (0.14 mg mL-1) > MT (0.21 mg mL-1). Antimicrobial tests showed Cu-T and Cu-TA gave better inhibition zone with more than 1.0 cm of inhibition zone compared to Fe and Al complexes. The immersion of the paint formulations into the seawater showed good performance until two months of life span. Fish nets coating with antifouling paint containing 15% Cu-T as antifoulant gave better results followed by Cu-TA, Cu2O, and Cu-OM. Meanwhile, fish nets that were coated with antifouling paint with the composition of Fe-T, Fe-TA, Al-T and Al-TA showed no significant differences among them. Thus, Cu-T can be the best candidate to be employed as an alternative antifoulant for antifouling paint in order to control the marine biofouling for fish cage nets in tropical areas.
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Biofouling significantly affect the outcome of aquaculture industry , due to the fouling of the fish nets.