Khairun Azizi Azizli

Effective removal of methylene blue from water using phosphoric acid based geopolymers: synthesis, characterizations and adsorption studies

Phosphoric acid based geopolymers (PAGPs) are a class of geopolymers that are produced by phosphoric acid activation of metakaolin. In this work, two different PAGPs have been synthesized using phosphoric acid to alumina molar ratios of 1 : 1 and 1.2 : 1. The surface profile, chemical composition, micromorphology, and texture properties of the geopolymers were instrumentally determined. Both geopolymers have shown a mesoporous profile with the avg. pore size of 8.6 and 19.4 nm by GP-1M (P : Al = 1 : 1) and GP-2M (P : Al = 1.2 : 1), respectively. Thermogravimetric analysis revealed that these geopolymers were thermally stable up to 800 °C, although the formation of quartz, cristobalite and tridymite was observed in XRD analysis of the samples treated at 800 °C for two hours. The synthesized geopolymers were utilized for the adsorption of methylene blue (MB) by investigating the effect of the amount of adsorbent, pH of the solution and shaking period. The batch kinetics study fitted best into the pseudo second order (PSO) reaction kinetic model. In isotherm modelling studies, the Langmuir isotherm model was best fitted and was used to describe the mechanism of the adsorption. Experimental adsorption capacities (qe) of 2.84 and 3.01 mg g−1 were recorded for GP-1M and GP-2M, respectively. Used adsorbents were successfully regenerated by furnace treatment at 400 °C for two hours, and the regenerated adsorbents presented enhanced adsorption capacities in the range of 4.9–5.07 mg g−1 for five repeat cycles, elucidating that the material is suitable for multiple time use.

The Potential of Microencapsulated Self-healing Materials for Microcracks Recovery in Self-healing Composite Systems: A Review

ABSTRACT The autonomic self-healing materials based on microcapsules have made major advancements for the repairing of microcracks in polymers and polymer composite systems. Self-healing encapsulated materials have the inborn ability to heal polymeric composites after being damaged by chemical and mechanical progressions. These intelligent micro-encapsulated self-healing materials possess great capabilities for recovering the mechanical as well aesthetic properties and barrier properties of the polymeric structures. Based on real world observations and experimental data, it is believed that microcracks and microcracking in polymeric materials can result because of many chemical and physical routes and is one of the foremost critical issues for polymeric materials. Especially in polymeric coatings, these microcracks can lead towards disastrous failure, and conventional healing systems like patching and welding cannot be used to repair microcracks at such a micro-level. Self-healing materials, especially, capsule based self-healing materials is a new field sought as an alternative to the conventional repairing techniques, requiring no manual intrusion and uncovering. This review covers the basic and major aspects of the microencapsulated self-healing approach like the effect of synthesis parameters on the size of microcapsules, healing efficiency determination, and the potential of the existing developed microencapsulated agents.

Comparison of Using NaOH and KOH Activated Fly Ash-Based Geopolymer on the Mechanical Properties

Geopolymer synthesis has two main requirements to fulfil which are the source material that is rich in Silicon (Si) and Aluminum (Al) and alkali activator such as sodium/potassium hydroxide. Sodium hydroxide (NaOH) is widely used for the synthesis of geopolymer compared to potassium hydroxide (KOH) with addition of silicate solution for the purpose of increasing dissolution process. However, the comparison of using different activator in the absence of silicate solution for geopolymer synthesis is not well established. This paper presents an evaluation on compressive strength of fly ash–based geopolymer by using different activator (KOH and NaOH) with respect to different curing conditions (time and temperature) in the absence of sodium silicate. The samples were mixed using mortar mixer and prepared in 50mm x 50mm x 50mm mould for determination of compressive strength. It can be observed that the highest compressive strength up 65.28 MPa was obtained using NaOH. Meanwhile, synthesis using KOH only recorded 28.73 MPa. The compressive strength was better when cured at elevated temperature (60°C) than room temperature (25°C). Further analysis on the microstructure of the highest compressive strength geopolymer samples for both activators was carried out using Field Emission Scanning Microscopy (FESEM) and Raman spectroscopy.

Simultaneous preparation of nano silica and iron oxide from palm oil fuel ash and thermokinetics of template removal

Nanomaterials have potential applications in the fields of catalysis, drug delivery, nanocomposites, and nanofluids. This study suggests a method for simultaneous preparation of nano silica and iron oxide from palm oil fuel ash (POFA). First, POFA was leached out with H2SO4 followed by alkali (NaOH) leaching. Basification (pH = 14) of the filtrate of the first leaching process produced iron oxide, while acidification of the alkali leachate produced nano silica. Addition of polymeric surfactant polyethylene glycol (PEG MW 20000) resulted in deagglomeration of the silica nanoparticles. Silica nanoparticles with sizes in the range of 20–80 nm, surface area of 326 m2 g−1, and pore diameter of 8.2 nm were obtained. Thermokinetic and thermodynamic studies of template (PEG) removal from the silica matrix were performed using the Kissinger and Ozawa methods based on model-free kinetics. The activation energy of PEG decreased from 330 kJ mol−1 to 140 kJ mol−1 when it was used as a template; this result demonstrates the lack of chemical bonding between the surfactant and silica. The findings are supported by the Fourier-transform infrared spectra of the PEG–silica composites.

Effect of Solid/Liquid Ratio during Curing Time Fly Ash Based Geopolymer on Mechanical Property

Geopolymer is produced from the alkali activation of materials rich in Si and Al such as fly ash. Based on the experimental and characterization result, solid to liquid ratio influenced the setting time and compressive strength of geopolymer in order to have good mechanical property. The optimum setting time and compressive strength were obtained at 3 : 1 solid to liquid ratio. Optimum curing time reach at 14 days.

Effect of Solid to Liquid Ratio on the Mechanical and Physical Properties of Fly Ash Geopolymer without Sodium Silicate

Geopolymer is produced from the alkali activation of materials rich in Si and Al with addition of silicate solution in order to improve the mechanical property. Limited research has been done with the absence of silicate solution in the geopolymerization process by varying solid/liquid ratio and on how it works for that condition on mechanical and physical properties. This paper presents an investigation on the mechanical and physical properties of fly ash based geopolymer by varying solid to liquid ratio using sodium hydroxide as the only activator. In addition, the strength development also been investigated. The samples were prepared using 50mm x 50mm x 50mm mould and cured at an elevated temperature (60oC). It can be observed that the optimum compressive strength and density were obtained at solid/ liquid ratio of 4. In addition, the compressive strength of fly ash based geopolymer for all the solid to liquid ratio increased until 14 days and started to decrease later.

The Effect of Si/Al Ratio and Sodium Silicate on the Mechanical Properties of Fly Ash Based Geopolymer for Coating

The present study has been performed to see the effect of varying Si/Al ratio (1.85 to 3) by using same concentration of NaOH and same solid/water ratio for the development of mechanical properties at 28 days of room temperature and also select the Si/Al ratio for coating application. The performance of the geopolymer was investigated on the basis of compressive strengthSEM along with EDS. Pure sodium hydroxide specimens displayed decreased strength. However the combination of sodium hydroxide and sodium silicate specimen with aSi/Al ratio of 2 showed maximum strength, whereas the specimen after Si/Al ratio 2 showed decrease in strength.

The Role of Surface Area of ZnO Nanoparticles as an Agent for some Chemical Reactions

Synthesising zinc oxide nanoparticles (ZnO-NPs) to get certain characteristics to be applied in Enhanced Oil Recovery (EOR) is still challenging to date. In this work, the importance of high surface area of ZnO nanoparticles as EOR agent was highlighted. A simulation on density of state (DOS), band structure and adsorption energy of hydrogen and nitrogen gases on the surface of ZnO was carried out; it is observed that from the band structure of the band gap value for ZnO is 0.808ev. For the ZnO, Zn 4s states contribute to conduction band and O 2p states contribute to valence band. ZnO-NPs were synthesised using the sol-gel method by dissolving zinc nitrate hexahydrate in nitric acid and varying the stirring time (1 and 24h) and sintering time (30 and 40 min). A microwave oven was used for annealing ZnO without insulating the samples in any casket. The results show that 30 and 40 min of annealing and stirring for 1 & 24 h influenced the morphology and size of ZnO-NPs. These parameters could be tailored to generate a range of nanoparticle morphology (flask and/with agglomerated nanoparticles in a corn shape) obtained by Field Emission Scanning Electron Microscope (FESEM) and hexagonal crystal, determined by X-ray diffractometer (XRD), with the mean size of 70.5 & 74.9 nm and a main growth at the peak (101). The prepared sample via stirring for 24h and sintering for 40 min was chosen to prepare ZnO nanofluid because it has the highest surface area (BET) among the rest of samples, 0.23 m2/g. 10% of Original Oil In Place (OOIP) was recovered successfully to prove that ZnO is a good candidate to be applied in some chemical reactions. Moreover, it was found that ZnO is a promising catalyst for ammonia synthesis based on the adsorption energy of hydrogen and nitrogen gases (-1.05 and-1.60 kcal/mol respectively).

Review on Reinforcement of Aerogel for Development of Advanced Nano Insulation Material for Application in Sustainable Buildings

Installation of insulation materials in buildings can reduce the usage of air conditioners by retarding heat flow into the building. Aerogel is one of the best insulation materials with distinctive properties that can replace existing building insulation materials such as fibre glass and polyurethane. However, brittleness of Aerogel makes it difficult to handle and disqualifies its viability as a building insulation material. Reinforcement of Aerogel with binding materials can improve its mechanical and thermal properties to overcome its brittleness. However, only a few studies have been carried out on this area. Furthermore, from the few existing studies, vital information such as thermal conductivity and specific application of the reinforced Aerogel studied were not considered. As an initiative to fill in this research gap, a review on reinforcement of Aerogel is presented.

Water Uptake Behavior of Lignin Modified Starch Film

A biodegradable urea crosslinked starch film was prepared. To improve the water resistance, the urea crosslinked starch system was reinforced with 5%, 10%, and 15% lignin. The prepared films were immersed in distilled water at three different temperatures, 25°C, 35°C and 45°C to study the behavior of water uptake. The addition of lignin effectively decreases water uptake as proven by lower water uptake equilibrium. Diffusion coefficient was calculated from the kinetic water uptake profile using the slope method of Fick’s second law for thin slab model. The calculated diffusion coefficient decreases as the lignin is increased. The diffusion coefficient is found to be dependent on the temperature. As more lignin is added to the system, higher activation energy is obtained due to the hydrophobicity of lignin.