Peter Adeniyi Alaba

Efficient biodiesel production via solid superacid catalysis: A critical review on recent breakthrough

Biodiesel produced from triglycerides and/or free fatty acids (FFAs) by transesterification and esterification has attracted immense attention during the past decades as a biodegradable, renewable and sustainable fuel. Currently, the use of solid superacid catalysts has proved a more efficient and “green” approach due to avoidance of environmental and corrosion problems and reduced product purification procedures. However, it is less viable economically because the reusability is low due to the lack of a hydrophilic/hydrophobic balance in the reactions that involve the use of inedible feedstock with a high water content. Therefore, this study gives a critical review on recent strategies towards efficient and “green” production of biodiesel via solid superacid catalysis. The strategies discussed include alkyl-bridged organosilica moieties functionalized hybrid catalysis to improve the hydrothermal stability of superacid catalysts, pre- and in situ water removal, and process intensification via temperature profile reduction. The strategies enabled well-defined porosity and an excellent hydrophobicity/hydrophilicity balance, which suppressed deactivation by water and glycerol.

A review of electrocoagulation technology for the treatment of textile wastewater

Abstract The conventional coagulation technique of textile wastewater treatments is plagued with the issue of low removal rate of pollutants and generation of a large quantity of sludge. Recently, electrocoagulation (EC) technique gained immense attention due to its efficiency. The technique involves dissolution of the sacrificial anodes to provide an active metal hydroxide as a strong coagulant that destabilizes and amasses particles and then removes them by precipitation or adsorption. EC process is influenced by operating parameters such as applied current density, electrodes material and configuration, type of electrical connection, pH and conductivity of the solution, and mixing state. Consequently, this work reviewed the major and minor reactions of EC process with operational parameters, design of EC cell, mass transfer studies and modeling, and industrial wastewater applications. The work also includes comparison of EC technique with conventional coagulation and combinations with other techniques. Special emphasis is on removal of pollutants from textile wastewater. Further, the electrical energy supplies and cost analysis are also discussed. Even though several publications have covered EC process recently, no review work has treated the systematic process design and how to minimize the effect of passivation layer deposited on the surface of the electrodes. EC process with rotating electrodes has been recommended to reduce this phenomenon. The effect of electrodes geometry is considered to enhance the conductivity of the cell and reduce energy consumption. The studies of ionic mass transfer were not implemented before special by limiting current method during the EC process. Moreover, no aforementioned studies used computational fluid dynamics modeling to present the mass transfer inside the EC reactor.

Insight into catalyst deactivation mechanism and suppression techniques in thermocatalytic deoxygenation of bio-oil over zeolites

Abstract The economic viability of the thermocatalytic upgrade of biomass-derived oxygenates is facing the challenge of low-quality products. This is because of leaching of active species, coking, and concomitant catalyst deactivation. These cumulate into the loss of catalytic activity with time on stream (TOS), which causes low degree of deoxygenation. Thus, this article reviews recent advances aimed at alleviating these setbacks to make the process viable for industrial scale-up. To understand the concept of catalyst deactivation and to offer solutions, the review scrutinized the deactivation mechanism diligently. The review also analyzes deactivation-suppression techniques such as nanocrystal zeolite cracking, hydrogen spilt-over (HSO) species, and composite catalysts (hybrid, hierarchical mesoporous zeolite, modified zeolites, and catalytic cracking deposition of silane). Interestingly, these deactivation-suppression techniques enhance catalytic properties mostly by reducing the signal strength of strong acid sites and increasing hydrothermal stability. Further, the approaches improve catalytic activity, selectivity, and TOS stability because of the lower formation of coke precursors such as polynuclear aromatics. However, despite these many advances, the need for further investigations to achieve excellent catalytic activity for industrial scale-up persists.

Kaolinite properties and advances for solid acid and basic catalyst synthesis

Historically, clay mineral catalysts have found industrial applications since the early 1930s. However, inherent limitations such as impurities, porosity, low surface area and acidity hindered their wide and sustained acceptability, this is despite their economic advantages. Interestingly, the use of kaolinite as precursor in active catalyst synthesis has been a breakthrough for several industrial processes such as petrol chemistry; especially in catalytic refining and bulk chemistry. The same is also true for processes that require solid acid catalysts, catalyst support, co-catalyst or promoter application for positive environmental impact and economic viability. Therefore, this article reviews the physicochemical properties of kaolinite and their amenability to modification towards enhancing their catalytic properties. The article also discussed modification methods such as mechanochemical activation (dealumination), thermal activation, intercalation and chemical activation. With more advances in technology and long-term commitment to investments, kaolinite will become the ideal catalyst and precursor for synthesizing novel catalysts for a sustainable “greener” future.

Synthesis and characterization of hierarchical nanoporous HY zeolites from acid-activated kaolin

Abstract Hierarchical nanoporous HY zeolites were synthesized from acid-activated kaolin. The hierarchical factor (HF) was maximized by varying the aging and crystallization time. This was achieved by maximizing the external surface area without greatly reducing the micropore volume. The resulting products were characterized using X-ray diffraction (XRD), X-ray fluorescence, N2 adsorption, and NH3 temperature-programmed desorption. The nanoporous HY zeolite with the highest HF was obtained by aging for 48 h and a crystallization time of 24 h. The acidity and crystallinity varied depending on the operating parameters. Incorporation of an appropriate amount of NaCl was also vital in maximizing the HF, crystallinity, and acidity. The sample crystallinities were determined by comparing their XRD peak intensities with those of a conventional Y zeolite. The results show that optimizing this process could lead to a widely acceptable commercial route for HY zeolite production.

Fishmeal replacement with Spirulina Platensis and Chlorella vulgaris in African catfish ( Clarias gariepinus ) diet: Effect on antioxidant enzyme activities and haematological parameters

This study explored fishmeal replacement with two freshwater microalgae: Spirulina Platensis and Chlorella vulgaris in African catfish (Clarias gariepinus) diet. The effect of inclusion of the two microalgae on biomarkers of oxidative stress, haematological parameters, enzyme activities and growth performance were investigated. The juvenile fish were given 3 distinct treatments with isonitrogenous (35.01-36.57%) and isoenergetic (417.24-422.27 Kcal 100 g-1) diets containing 50% S. platensis (50SP), 75% S. platensis (75SP), 50% C. vulgaris (50CL), 75% C. vulgaris (75CL) and 100% fishmeal (100% FM) was used as the control diet. The result shows that all the diets substituted with both S. platensis, and C. vulgaris boosted the growth performance based on specific growth rate (SGR) and body weight gain (BDWG) when compared with the control diet. The feed conversion ratio (FCR) and protein efficiency ratio (PER) was significantly influenced by all the supplementations. The haematological analysis of the fish shows a significant increase in the value of red and white blood cells upon supplementation with 50SP and 50CL but decrease slightly when increased to 75SP and 75CL. Furthermore, the value of haematocrit and haemoglobin also increased upon supplementation with 50SP and 50CL but decrease slightly when increased to 75SP and 75CL. The white blood cell (WBC), red blood cell (RBC) increased, while total cholesterol (TCL), and Plasma glucose levels decreased significantly upon supplementation of algae. This is a clear indication that S. platensis and C. vulgaris are a promising replacement for fishmeal, which is a source protein in the C. gariepinus diet.

Bactericidal effect of silver nanoparticles against the propagation of Clavibacter michiganensis infection in Lycopersicon esculentum Mill

This study explored the use of silver nanoparticle as a bactericidal against the propagation of Clavibacter michiganensis onto tomatoes (Lycopersicon esculentum Mill). In Mexico, tomato production covers about 73% of the total vegetable production but it is affected by outbreak of bacteria canker caused by Clavibacter michiganensis subspecies michiganensis (Cmm). Silver ions possess inhibitor properties, bactericides and high specter antimicrobials. In this study, 6 groups of culture were prepared using 6 different petri dishes where silver nanoparticles of varying concentrations (120, 84, 48, 24, 12 and 0 μg) were added. Furthermore, each group was observed for 20 min, 1, 2, 12 and 24 h. The optimum concentration is 84 μg, which shows an average of 2 Cmm colonies after 20 min. Further increase to 120 μg shows no significant change. However, the average colonies was observed for 48 μg after 1, 2, 12, and 24 h. The obtained results indicate that silver nanoparticles are a promising inhibitor, bactericide and high a specter antimicrobial for treatment or prevention of Cmm.

Toward N-nitrosamines free water: Formation,prevention, and removal

ABSTRACT This study elucidates the recent trends in the formation, prevention, and removal of N-nitrosamines such as N-nitrosodimethylamine (NDMA) from wastewater or drinking water. Reports are rife on the occurrence of NDMA in areas such as amine degradation during postcombustion CO2 capture (PCC), chlorinated/chloraminated and ozonated drinking water, smoked or cooked foods personal care, tobacco and pharmaceutical products. The major routes responsible for the formation of NDMA in portable waters include chlorination/chloramination and ozonation. The major NDMA precursors are secondary, tertiary, and quaternary amines such as dimethylamine, diethanolamine, and triethanolamine. Due to the environmental and public health concerns posed by this contaminant, a proactive approach is necessary towards suppressing their occurrence, as well as their removal. Consequently, this study critically reviewed the formation, prevention, and removal of N-nitrosamines. The study discussed NDMA prevention techniques, such as physical adsorption, pre-oxidation, and biological activated carbon. The removal techniques discussed here include physicochemical (such as combined adsorption and microwave irradiation and UV photolysis), bioremediation, catalytic reduction, and dope technology. Irrespective of the effectiveness and seemingly economic viability of some of these technologies, preventing the occurrence of NDMA right from the outset is more potent because the treatments consume more energy.