Mohanad El-Harbawi

Characteristics and oil sorption effectiveness of kapok fibre, sugarcane bagasse and rice husks: oil removal suitability matrix

The characteristics and water/oil sorption effectiveness of kapok fibre, sugarcane bagasse and rice husks have been compared. The three biomass types were subjected to field emission scanning electron microscopy-energy dispersive X-ray spectroscopy and surface tension analyses for liquid–air and oil-water systems were conducted. Both kapok fibre and sugarcane bagasse exhibit excellent oil sorption capabilities for diesel, crude, new engine and used engine oils as their oil sorption capacities all exceed 10 g/g. The synthetic sorbent exhibits oil sorption capacities comparable with sugarcane bagasse, while rice husks exhibit the lowest oil sorption capacities among all the sorbents. Kapok fibre shows overwhelmingly high oil-to-water sorption (O/W) ratios ranging from 19.35 to 201.53 while sugarcane bagasse, rice husks and synthetic sorbent have significantly lower O/W ratios (0.76–2.69). This suggests that kapok fibre is a highly effective oil sorbent even in well-mixed oil–water media. An oil sorbent suitability matrix is proposed to aid stakeholders in evaluating customized oil removal usage of the natural sorbents.

Development of a novel mathematical model using a group contribution method for prediction of ionic liquid toxicities

A new mathematical model has been developed that expresses the toxicities (EC₅₀ values) of a wide variety of ionic liquids (ILs) towards the freshwater flea Daphnia magna by means of a quantitative structure-activity relationship (QSAR). The data were analyzed using summed contributions from the cations, their alkyl substituents and anions. The model employed multiple linear regression analysis with polynomial model using the MATLAB software. The model predicted IL toxicities with R²=0.974 and standard error of estimate of 0.028. This model affords a practical, cost-effective and convenient alternative to experimental ecotoxicological assessment of many ILs.

Effect of imidazolium-based ionic liquids on bacterial growth inhibition investigated via experimental and QSAR modelling studies

Tuning the characteristics of solvents to fit industrial requirements has currently become a major interest in both academic and industrial communities, notably in the field of room temperature ionic liquids (RTILs), which are considered one of the most promising green alternatives to molecular organic solvents. In this work, several sets of imidazolium-based ionic liquids were synthesized, and their toxicities were assessed towards four human pathogens bacteria to investigate how tunability can affect this characteristic. Additionally, the toxicity of particular RTILs bearing an amino acid anion was introduced in this work. EC50 values (50% effective concentration) were established, and significant variations were observed; although all studied ILs displayed an imidazolium moiety, the toxicity values were found to vary between 0.05 mM for the most toxic to 85.57 mM for the least toxic. Linear quantitative structure activity relationship models were then developed using the charge density distribution (σ-profiles) as molecular descriptors, which can yield accuracies as high as 95%.

Synthesis and anti-microbial activity of hydroxylammonium ionic liquids

Eight hydroxylammonium-based room temperature ionic liquids (ILs) have been synthesized by acid-base neutralization of ethanolamines with organic acids. The ILs were characterized by infrared and nuclear magnetic resonance spectroscopies and elemental analysis. Their anti-microbial activities were determined using the well-diffusion method. All eight ILs were toxic to Staphylococcus aureus, while 2-hydroxyethylammonium lactate and 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium acetate showed high anti-microbial activity against a wide range of human pathogens.

Synthesis and anti-microbial potencies of 1-(2-hydroxyethyl)-3-alkylimidazolium chloride ionic liquids: Microbial viabilities at different ionic liquids concentrations

Three 1-(2-hydroxyethyl)-3-alkylimidazolium chloride room temperature ionic liquids (ILs) [2OHimC(n)][Cl]; (n=0, 1, 4) have been synthesized from the appropriate imidazole precursors and characterized by IR and NMR spectroscopies and elemental analysis. Their anti-microbial activities were investigated using the well-diffusion method. The viabilities of Escherichia coli, Aeromonas hydrophila, Listeria monocytogenes and Salmonella enterica as a function of IL concentrations were studied. The minimal inhibitory concentrations (MICs) and EC₅₀ values for the present ILs were within the concentration range from 60 to 125 mM and 23 to 73 mM. The anti-microbial potencies of the present ILs were compared to a standard antibiotic, gentamicin. The finding affords additional perspective on the level of ILs toxicity to aquatic lifeforms and yet, this characteristic can be readily harnessed to detect microbial growth and activity.

Hazardous waste management: current status and future strategies in Malaysia

Although Malaysia is a model for economic success amongst Southeast Asian countries with its impressive development over the last 36 years, it has not been without its detrimental effects on the natural environment. The most apparent effect is the drastic increase in the generation of hazardous wastes. This paper highlights Malaysias current status in hazardous waste management and the potential major difficulties. The principles, objectives and the remedial plans for hazardous waste control are also explained in detail and have been stipulated in the environmental policies as issued by the Department of Natural Resources and Environmental Ministry, Malaysia.

Development of QSAR model to predict the ecotoxicity of Vibrio fischeri using COSMO-RS descriptors

Ionic liquids (ILs) are class of solvent whose properties can be modified and tuned to meet industrial requirements. However, a high number of potentially available cations and anions leads to an even increasing members of newly-synthesized ionic liquids, adding to the complexity of understanding on their impact on aquatic organisms. Quantitative structure activity∖property relationship (QSAR∖QSPR) technique has been proven to be a useful method for toxicity prediction. In this work,σ-profile descriptors were used to build linear and non-linear QSAR models to predict the ecotoxicities of a wide variety of ILs towards bioluminescent bacterium Vibrio fischeri. Linear model was constructed using five descriptors resulting in high accuracy prediction of 0.906. The model performance and stability were ascertained using k-fold cross validation method. The selected descriptors set from the linear model was then used in multilayer perceptron (MLP) technique to develop the non-linear model, the accuracy of the model was further enhanced achieving high correlation coefficient with the lowest value being 0.961 with the highest mean square error of 0.157.

Study of the antimicrobial activity of cyclic cation-based ionic liquids via experimental and group contribution QSAR model

Over the past decades, Ionic liquids (ILs) have gained considerable attention from the scientific community in reason of their versatility and performance in many fields. However, they nowadays remain mainly for laboratory scale use. The main barrier hampering their use in a larger scale is their questionable ecological toxicity. This study investigated the effect of hydrophobic and hydrophilic cyclic cation-based ILs against four pathogenic bacteria that infect humans. For that, cations, either of aromatic character (imidazolium or pyridinium) or of non-aromatic nature, (pyrrolidinium or piperidinium), were selected with different alkyl chain lengths and combined with both hydrophilic and hydrophobic anionic moieties. The results clearly demonstrated that introducing of hydrophobic anion namely bis((trifluoromethyl)sulfonyl)amide, [NTF2] and the elongation of the cations substitutions dramatically affect ILs toxicity behaviour. The established toxicity data [50% effective concentration (EC50)] along with similar endpoint collected from previous work against Aeromonas hydrophila were combined to developed quantitative structure-activity relationship (QSAR) model for toxicity prediction. The model was developed and validated in the light of Organization for Economic Co-operation and Development (OECD) guidelines strategy, producing good correlation coefficient R2 of 0.904 and small mean square error (MSE) of 0.095. The reliability of the QSAR model was further determined using k-fold cross validation.

Optimization, Kinetic and Equilibrium Studies of Disperse Yellow 22 Dye Removal from Aqueous Solutions Using Malaysian Teak Wood Sawdust as Adsorbent

Abstract Treatment of discharges/effluents containing residual dyes has been a topic of interest for long. Adsorption is a widely accepted process for the treatment of industrial discharges containing dyes. The search for replacement of commonly used adsorbents – activated carbon – by locally available materials has gained importance. Adsorption of disperse yellow 22 (DY 22) using wood dust from local saw mills to treat effluents was studied and has given promising results. The operating parameters of adsorption process, initial solution pH, initial concentration, adsorbent dosage, adsorbate-adsorbent contact time influencing adsorption of DY 22 dye onto activated sawdust (ASD), were investigated. The optimum conditions were obtained by using response surface methodology (RSM). The batch adsorption experimental data were analysed by using Lageregans pseudo-first-order and pseudo-second-order kinetic models and found that the adsorption of DY 22 onto ASD followed the pseudo-second-order kinetic model. The experimental data were fitted to Langmuir and Freundlichs isotherm models. The adsorption of DY 22 onto ASD was fitted satisfactorily with Langmuirs isotherm model with an adsorption capacity of 33.78 mg/g (R2 = 0.99). Based on the experimental investigations, it is suggested that ASD is a potential effectual adsorbent for the removal of DY 22 from aqueous solution.

Using geographic information systems in assessment of major hazards of liquefied petroleum gas

It is known that there are hazards associated with the storage, handling and use of liquefied petroleum gas. Storage process plants of dangerous substances define the set of risk sources. Release of chemical due to accident could be severe and poses an immediate effect to workers on‐site and communities off‐site as well as it causes adversely a potential effect on the environment. LPG is considered to be a very important fuel and chemical feed stock. The material has been involved in many major fires and explosions. This paper presents the most recent analysis techniques for evaluating several physical models. These models are used to calculate the physical effects of explosion and fire from LPG accidents and also to predict the affected area.