Elsevier

Bioresource Technology

Volume 281, June 2019, Pages 234-238
Bioresource Technology

Synergism of clay with zinc oxide as nanocatalyst for production of biodiesel from marine Ulva lactuca

https://doi.org/10.1016/j.biortech.2019.02.101Get rights and content

Highlights

Abstract

In the present work, Ulva lactuca, a marine macroalgae was used for the production of biodiesel. The ultrasound assisted extraction of oil from autoclaved algal biomass was found effective with maximum yield. The maximum oil was extracted at optimal conditions of 5% moisture content of algal biomass, 0.15 mm size of biomass, 6:1 solvent: solid ratio, at 55 °C in 140 min. The n-hexane with co-solvent methyl tertbutyl ether has shown higher oil when compared to other co-solvents. The extracted oil was transesterified into biodiesel using silica doped with zinc oxide as novel heterogeneous nanocatalyst. The maximum biodiesel yield of 97.43% was obtained at optimized conditions of 800 °C calcination temperature, 8% catalyst concentration, 9:1 methanol to oil ratio, 55 °C reaction temperature and 50 min reaction time. The kinetics of the transesterification reaction was also studied. The Ulva lactuca was found as a potential source for biodiesel production.

Introduction

As a result of near extinction of fossil fuels and reduced supply of renewable resources, it is highly necessary to find an alternate source for the sustainable production of biodiesel (Ahmed et al., 2010). Sustainable biomass feedstocks were found to be utilized for the conversion of energy sources. Marine macroalgae, one of the highly potential and favorable feedstock commonly referred as seaweeds were highly used for biodiesel production as they have high photosynthetic efficiency than other biomass for the conversion of energy sources (Briggs, 2008). This photosynthesis helps both micro and macro algae for the conversion of oil to biodiesel (Sandhyarani, 2010). Biodiesel are obtained by extracting oil from algal biomass various methods including solvent extraction, supercritical fluid extraction and oil press. Solvent extraction using n-hexane is highly appreciated for the extraction of oil (Tamilarasan et al., 2013). A novel heterogeneous catalyst has been adopted for transesterification process, as they are widely reused. This process does not require separate product recovery step, thus the purification is more simplified and has high yields of methyl esters (Cao et al., 2008).

In the present work, marine macro algae Ulva lactuca was used for extraction of algal oil for biodiesel production. The various parameters were optimized for maximum oil yield. Extracted algal oil was analysed using GC–MS analysis for fatty acid profile. In order to convert the algal oil in to biodiesel, a novel heterogeneous catalyst synthesized from waste clay and doped with zinc oxide was used for biodiesel production.

Section snippets

Materials

Solvents namely as n-hexane, methyl tertbutyl ether, diethyl ether, methylenechloride, 2-isopropanol and ethyl alcohol used for algal oil extraction and biodiesel production was purchased from SRL Pvt. Ltd., Mumbai, India. The Chemicals used for synthesis and doping of nanocatalyst such as Zinc acetate and Sodium hydroxide were procured from LobaChemie Pvt. Ltd., Mumbai, India. These analytical grade chemicals were used without any purification process.

Collection and pretreatment of algal biomass

Marine algae U. lactuca is a green algae

Optimization of pretreatment methods

The combination of ultrasound and autoclave was studied for its effective pre-treatment conditions. The oil yield of 12 ± 0.3% (g/g) was obtained when the samples were pre-treated with autoclave followed by ultrasonication. The increase in oil yield was achieved due to exposure of sample to lower temperature with release of high fraction of oil. This pre-treatment condition was also found to be effective as they utilized minimal solvents for extraction at shorter time. The obtained results were

Conclusions

Autoclave followed by ultrasonication for extraction of algal oil was found effective. The maximum oil yield of 10.54% (w/w) was achieved at optimized conditions of 5% moisture content, 0.15 mm biomass, 6:1 solvent:solid ratio, 55 °C extraction temperature, and 140 min extraction time. The size of 50–70 nm of the synthesized nanocatalyst was confirmed by XRD and SEM. The maximum biodiesel yield of 97.43% was obtained at optimum conditions of 8% catalyst concentration, 9:1 methanol: oil ratio,

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