Zahira Yaakob

An overview: biomolecules from microalgae for animal feed and aquaculture

Despite being more popular for biofuel, microalgae have gained a lot of attention as a source of biomolecules and biomass for feed purposes. Algae farming can be established using land as well as sea and strategies can be designed in order to gain the products of specific interest in the optimal way. A general overview of the contributions of Algae to meet the requirements of nutrients in animal/aquaculture feed is presented in this study. In addition to its applications in animal/aquaculture feed, algae can produce a number of biomolecules including astaxanthin, lutein, beta-carotene, chlorophyll, phycobiliprotein, Polyunsaturated Fatty Acids (PUFAs), beta-1,3-glucan, and pharmaceutical and nutraceutical compounds which have been reviewed with respect to their commercial importance and current status. The review is further extended to highlight the adequate utilization of value added products in the feeds for livestock, poultry and aquaculture (with emphasis in shrimp farming).

Steam-reforming of ethanol for hydrogen production

Production of hydrogen by steam-reforming of ethanol has been performed using different catalytic systems. The present review focuses on various catalyst systems used for this purpose. The activity of catalysts depends on several factors such as the nature of the active metal catalyst and the catalyst support, the precursor used, the method adopted for catalyst preparation, and the presence of promoters as well as reaction conditions like the water-to-ethanol molar ratio, temperature, and space velocity. Among the active metals used to date for hydrogen production from ethanol, promoted-Ni is found to be a suitable choice in terms of the activity of the resulting catalyst. Cu is the most commonly used promoter with nickel-based catalysts to overcome the inactivity of nickel in the water-gas shift reaction. γ-Al2O3 support has been preferred by many researchers because of its ability to withstand reaction conditions. However, γ-Al2O3, being acidic, possesses the disadvantage of favouring ethanol dehydration to ethylene which is considered to be a source of carbon deposit found on the catalyst. To overcome this difficulty and to obtain the long-term catalyst stability, basic oxide supports such as CeO2, MgO, La2O3, etc. are mixed with alumina which neutralises the acidic sites. Most of the catalysts which can provide higher ethanol conversion and hydrogen selectivity were prepared by a combination of impregnation method and sol-gel method. High temperature and high water-to-ethanol molar ratio are two important factors in increasing the ethanol conversion and hydrogen selectivity, whereas an increase in pressure can adversely affect hydrogen production.

Synthesis and characterization of Cu-Al layered double hydroxides

Abstract A series of Cu–Al hydrotalcite-like layered compounds has been synthesized by coprecipitation using metal nitrate precursors and sodium carbonate. The Cu/Al atomic ratio was varied between 0.5 and 4. The dried precipitates were characterized by powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The crystalline hydrotalcite-like phase was present as major component in all precipitates, the first time such crystalline phase was observed in the precipitates of the constituent metals ratio as low as 0.5. The malachite phase was also observed in variable amounts, and it became amorphous at low copper content.

Degradation and mineralization of methylene blue using a heterogeneous photo-Fenton catalyst under visible and solar light irradiation

A SiO2-supported Fe and Ni bimetallic catalyst has been synthesized, characterized and, for the first time, tested as a heterogeneous photo-Fenton catalyst for the degradation and mineralization of methylene blue (MB) dye. The morphological, structural, and optical properties of this catalyst were analyzed using FESEM, XRD, FTIR and UV–vis spectroscopy. The photocatalytic degradation of MB has been investigated using Fe–Ni/SiO2 catalysts under visible and solar light irradiation in aqueous solutions. The effects of solution pH, H2O2 concentration, initial MB concentration, catalyst dosage and light intensity on the degradation of MB have been systematically investigated. An almost complete degradation was achieved within 60 min with a solution pH of 3.00, a H2O2 concentration of 3.0 mM L−1 and a catalyst dose of 0.85 g L−1. The degradation and total organic carbon (TOC) removal efficiencies were 99.80% and 86.19%, respectively, for sunlight. However, the values were only 99.01% and 75.71% for visible light. These results suggested that Fe–Ni/SiO2 possesses significant catalytic activity, and the solar-Fenton process is a feasible method for degrading and mineralizing the MB dye compared with artificial visible light. The catalytic action is attributed to H2O2 and the formation of hydroxyl radicals (˙OH) by Fe(III) in Fe–Ni/SiO2via the photo-Fenton reactions. Furthermore, we determined that the catalyst activity can be replicated in successive experiments without a significant decline in the Fe–Ni/SiO2 and H2O2 processing efficiency under light irradiation. Our results will be useful for future improvement of active heterogeneous photo-Fenton catalysts for developing organic dye-containing wastewater treatments.

Microwave-assisted transesterification of jatropha and waste frying palm oil

The utilisation of non-edible oil as a biodiesel feedstock is expected to minimise the utilisation of food-grade oil for industrial applications. The microwave-assisted transesterification process was adopted to obtain the biodiesel from jatropha oil and waste frying palm oil (WFPO). The transesterification process was carried out in the presence of methanol with a methanol to oil ratio of 12:1 and a catalyst (sodium hydroxide). The effect of transesterification reaction parameters such as quantity of the catalyst, reaction temperature and time on the biodiesel yield and purity has been investigated. The optimised reaction temperature, time and catalyst concentration was 65 °C, 7 min and 1% by weight, respectively. The highest percentage yield (89.7 for jatropha and 88.63 for WFPO) and purity (99.65 for jatropha and 99.45 for WFPO) of biodiesel was observed with the optimised process parameters. The fuel properties of the obtained biodiesel were tested according to European Union draft standards. The obtained results suggested that microwave radiation may be employed in the transesterifcation process to reduce the reaction time and temperature.

Utilization of palm empty fruit bunch for the production of biodiesel from Jatropha curcas oil

Transesterification reaction of Jatropha curcas oil with methanol was carried out in the presence of ash generated from Palm empty fruit bunch (EFB) in a heterogeneous catalyzed process. The ash was doped with KOH by impregnation to achieve a potassium level of 20 wt.%. Under optimum conditions for the EFB-catalyzed (65 °C, oil/methanol ratio of 15, 90 min, 20 wt.% EFB ash catalyst) and the KOH-EFB-catalyzed reactions (65 °C, oil/methanol ratio of 15, 45 min, 15 wt.% of KOH doped EFB ash), biodiesel (>98%) with specifications higher than those stipulated by European biodiesel quality standard EN 14214 was obtained.

CeO2-TiO2 as a visible light active catalyst for the photoreduction of CO2 to methanol

The performance of CeO2-TiO2 photocatalyst for the photocatalytic reduction of CO2 into methanol was studied under visible light irradiation. The as-prepared catalysts were characterized for their structural, textural and optical properties using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), nitrogen physisorption analysis, UV-vis spectroscopy and photoluminescence (PL) spectroscopy. The characterization results indicated that the presence of CeO2 stabilized the anatase phase of TiO2, decreased its crystallite size, increased the surface area, reduced the band gap energy and lowered the rate of electron-hole pair recombination. The CeO2-TiO2 photocatalyst showed an increased methanol yield of 18.6 µmol/g under visible light irradiation, compared to the bare TiO2 (6.0 µmol/g).

An enthusiastic glance in to the visible responsive photocatalysts for energy production and pollutant removal, with special emphasis on titania

As a consequence of the rapid growth of industry, major problems are created related to energy and environment. Sunlight being one of the most potential alternative source of energy, the development of efficient solar-energy storage systems is an important subject in the fields of science and technology. Here we have reviewed and summarized some of the recent reports on visible responsive photocatalysts. In this review, the influence of various metal oxide photocatalysts on energy production and pollutant removal are presented with special emphasis on titania based photocatalysts. The photoactivity of titania for various pollutant degradation, modified titania (TiO2) systems, their physical and chemical characteristics, and so forth, are described in detail at this juncture. Different methods used to enhance the visible light absorption of TiO2, like doping with metals and nonmetals, coupling with other metal oxides, and so forth, have been discussed. Various applications of photocatalysts including photocatalytic treatment of waste water, pesticide degradation and water splitting to produce hydrogen are summarized. The development of photocatalysts that function under visible light for the efficient utilization of sunlight is an area of current interest and thus the different methods of preparation for the visible active photocatalysts are also explored.

Sol-gel synthesis, characterisation, and photocatalytic activity of porous spinel Co3O4 nanosheets

Mesoporous spinel Co3O4 nanosheets were synthesised via a simple sol-gel route using the Pluronic P123 triblock copolymer as the stabilising agent. Their structural, morphological, and textural properties were characterised. FTIR spectrum revealed the formation of cobalt oxide without any surface adsorbed impurities. Face centered cubic phase of spinel Co3O4 with the mean crystalline size of 26 nm was assigned by the X-ray diffraction analysis without the formation of other phases. Porous nanosheets and cave-like morphologies were identified from the scanning electron microscopy (SEM) images. Highly agglomerated more or less spherical particles with well separated lattice fringes, representing the oriented growth of nanocrystals, were noticed on the transmission electron microscopy photographs. Surface area analysis revealed that the spinel has high surface area of about 25 m2 g−1 with monomodal mesoporosity. The average pore size distribution was found to be about 15.8 nm. The as-prepared spinel photocatalyst showed a mild photocatalytic activity in the degradation of methylene blue (2.5 mg L−1) under UV light irradiation with air as the oxidising agent. Photocatalytic activity of the as-prepared reusable Co3O4 was found to be higher than that of the commercial spinel powder.

Review of hydrogen production via glycerol reforming

Owing to the high energy content of hydrogen and the possibility of converting this energy in fuel cell devices into electric power without any pollutant emissions, hydrogen has grown to be one of the most useful sources of energy, especially if it is produced from renewable sources. In recent years, the development of an efficient process for hydrogen production has become an important goal for energy researchers. Numerous studies have evaluated the catalytic reforming of glycerol for hydrogen production both experimentally and thermodynamically. To enhance hydrogen production and make the production process efficient, researchers have investigated different reforming processes under a wide range of operating conditions. Moreover, the main focus of these studies was the development of a high-performance reforming catalyst that can increase the hydrogen yield and decrease carbon formation and processing costs. Several reforming processes can be used to produce hydrogen from glycerol. This article reviews these reforming processes with emphasis on the common catalysts and the operating conditions used in thermodynamic analyses and experimental work. Although most of these studies have been conducted on steam and aqueous-phase reforming processes, more work on other reforming processes, such as autothermal reforming, partial oxidation, supercritical water, and photo-catalytic reforming, has yet to be completed.