Megat Azmi Megat Johari

Removal of copper from water using limestone filtration technique: determination of mechanism of removal

This paper discusses heavy metal removal from wastewater by batch study and filtration technique through low-cost coarse media. Batch study has indicated that more than 90% copper (Cu) with concentration up to 50 mg/l could be removed from the solution with limestone quantity above 20 ml (equivalent to 56 g), which indicates the importance of limestone media in the removal process. This indicates that the removal of Cu is influenced by the media and not solely by the pH. Batch experiments using limestone and activated carbon indicate that both limestone and activated carbon had similar metal-removal efficiency (about 95%). Results of the laboratory-scale filtration technique using limestone particles indicated that above 90% removal of Cu was achieved at retention time of 2.31 h, surface-loading rate of 4.07 m3/m2 per day and Cu loading of 0.02 kg/m3 per day. Analyses of the limestone media after filtration indicated that adsorption and absorption processes were among the mechanisms involved in the removal processes. This study indicated that limestone can be used as an alternative to replace activated carbon.

Ammoniacal nitrogen and COD removal from semi-aerobic landfill leachate using a composite adsorbent: Fixed bed column adsorption performance

The performance of a carbon-mineral composite adsorbent used in a fixed bed column for the removal of ammoniacal nitrogen and aggregate organic pollutant (COD), which are commonly found in landfill leachate, was evaluated. The breakthrough capacities for ammoniacal nitrogen and COD adsorption were 4.46 and 3.23 mg/g, respectively. Additionally, the optimum empty bed contact time (EBCT) was 75 min. The column efficiency for ammoniacal nitrogen and COD adsorption using fresh adsorbent was 86.4% and 92.6%, respectively, and these values increased to 90.0% and 93.7%, respectively, after the regeneration process.

Removal of ammoniacal nitrogen and COD from semi-aerobic landfill leachate using low-cost activated carbon?zeolite composite adsorbent

A carbon-zeolite composite adsorbent has been studied for COD and ammoniacal nitrogen removal in semi-aerobic landfill leachate. The optimum conditions for adsorption in the batch study occurred at pH 7, shaking speed of 200 rpm, and contact time of 105 min. The Langmuir isotherms corresponded slightly better than Freundlich isotherm for both ammoniacal nitrogen and COD removals. The Langmuir adsorption capacities for ammonia and COD were 27.47 mg/g and 22.99 mg/g, while the Freundlich adsorption capacities were 0.4227 mg/g and 0.0642 mg/g, respectively. The overall rate of the ammonia and COD adsorption processes appears to be dominated by chemisorption process.

The relationship between substrate roughness parameters and bond strength of ultra high-performance fiber concrete

The bonding that exists between the old concrete and the new concrete depends largely on the quality of substrate surface preparation. The accurate representation of substrate surface roughness can help determine very precisely the correct bonding behavior. In this work, an experimental investigation was carried out to quantify the normal concrete (NC) substrate roughness parameters and evaluate their relationship with the bonding performance of ultra high-performance fiber concrete (UHPFC), used as a repair material. The bond strength was quantified based on the results of the pull-off test, splitting cylinder tensile test, and the slant shear test. Three types of NC substrate surface preparation were used: as-cast (without surface preparation) as reference, wire-brushed, and sand-blasted (SB); the roughness of which was determined using an optical three-dimensional (3D) surface metrology device (Alicona Infinite Focus). It was observed from the result of the pull-off test that failure occurred in the substrate, even though adequate substrate surface roughness was provided. Moreover, analysis of the splitting cylinder tensile and slant shear test results showed that the substrate surface preparation method had a significant influence in bonding strength between UHPFC and the NC substrate. The composite UHPFC/NC substrate having a SB surface behaved closely as a monolithic structure under splitting and slant shear tests. An excellent correlation (R 2 > 85%) was obtained between the substrate roughness parameters and the results of the splitting cylinder tensile and slant shear tests.

The Role of Silica Fume in the Adhesion of Concrete Restoration Systems

The weak interfacial transition zone between new and old concrete is always paid much attention and controls many properties of repaired concrete, The present work reports a study on the influence of the silica fume on the adhesion of reactive powder concrete (RPC), as a concrete restoration material, with the ordinary concrete (OC) substrate. The results showed that, the silica fume presence in the interfacial transition zone significantly enhances the adhesion strength between RPC and OC substrate. Furthermore, the silica fume particles consume calcium hydroxide, which is in attendance in the interfacial transition zone, and make the zone more dense, uniform and tough.

Strength and permeability properties of concrete containing rice husk ash with different grinding time

The compressive concrete strength and the gas permeability properties over varying fineness of the rice husk ash were experimentally investigated. The relationships among them were analyzed. In this study eight samples made from the rice husk ashes with a different grain size were used, i.e. coarse original rice husk ash 17.96 μm (RHA0), 10.93 μm (RHA1) 9.74 μm (RHA2), 9.52 μm (RHA3), 9.34 μm (RHA4), 8.70 μm (RHA5), 6.85 μm (RHA6) and 6.65 μm (RHA7). The ordinary Portland cement was partially replaced with the rice husk ash (15 wt%). The test results showed that the RHA3 produced the concrete with good strength and low porosity. Additionally the strength of the concrete was improved due to the partial replacement of RHA3 material in comparison with normal coarse rice husk ash RHA0. On the other hand the influence of OPC and RHA materials on the concrete permeability was affected by the grinding time and age (i.e., curing time). The permeability coefficient decreased with the increasing of curing time. The relationships between compressive strength and permeability coefficient are greatly affected by curing times and are sensitive to the grinding cementitious systems.

Microstructural analysis of the adhesion mechanism between old concrete substrate and UHPFC

The performance of any repaired concrete structure, and thus its service life, depends on the quality of the interfacial transition zone of the composite system formed by the repair material and the existing concrete substrate. In this work, the properties of the interfacial transition zone between normal concrete (NC) substrate as an old concrete and ultra-high performance fiber-reinforced concrete (UHPFC) as a repair material was investigated. Pull-off and splitting cylinder tensile tests were performed to quantify the bond strength in direct and indirect tensions, respectively. The microstructure of the interfacial transition zone was also studied using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS). Different types of NC substrate surface preparation methods were used. An optical three-dimensional surface metrology device was used to estimate the substrate roughness parameters. Based on the results, high interfacial bond strength was achieved on the 3rd, 7th, and 28th days. The pull-off test results revealed that all failures occurred in the substrate, regardless of the substrate surface roughness. The majority of failures in the split tensile test also occurred in the substrate. SEM/EDS proved that the use of UHPFC as a repair material chemically, physically, and mechanically improved the repaired interfacial transition zone to become stronger and denser, as well as more uniform, and durable. Moreover, the use of UHPFC increased the service life of repaired structures and minimized the number and extent of interventions to the lowest possible level.

Characteristics of Treated Palm Oil Fuel Ash and its Effects on Properties of High Strength Concrete

Palm oil fuel ash obtained from palm oil mill was treated via screening, grinding and heating to improve its pozzolanic reactivity. The characteristics of the palm oil fuel ash before and after treatment were monitored to assess the changes in the properties of the palm oil fuel ash. The resulting ultrafine palm oil fuel ash was then utilized to produce high strength concrete by replacing the ordinary Portland cement at 0, 20, 40 and 60% on mass-for-mass basis. The results show that the treatment process undertaken reduces the particle size, diminishes the unburned carbon content, while at the same time increases the glassy phases. The utilization of the ultrafine palm oil fuel ash in high strength concrete was observed to improve workability especially at higher ultrafine palm oil fuel ash content. In addition, the long-term compressive strength of the high strength concrete was significantly increased with the ultrafine palm oil fuel ash inclusion. Further, the long-term rapid chloride permeability was significant reduced especially at higher ultrafine palm oil fuel ash content of 60%, which could be translated into superior durability performance.

Strength and Microstructural Performance of Nano-SiO2 Gel (NSG) Infused Alkaline Activated Ground Blast Furnace Slag-Ultrafine Palm Oil Fuel Ash (AAGU) Based Mortar

The aim of this paper is to study the performance of infused nanoSiO2 gel (NSG) on the developed alkaline activated binary blending of ground blast furnace slag (GBFS) and ultrafine palm oil fuel ash (UPOFA) based mortar (AAGU) using the constant mass of combined activators (10 M NaOHaq+Na2SiO3aq (Ms = SiO2/Na2O=3.3)). The methods include using the 3-day compressive strength results and microstructural characterization (SEM+EDX and FTIR). The finding revealed that the compressive strength of the mortar increased with NSG and the maximum strength achieved was 57.3 MPa signifying 21% strength gain compared to NSG-free sample. The NSG also played the role of microcracks and pore fillings, increased the product homogeneity and reduced its amorphousity due to silicate re-organization but has no effects on Si-Al substitution.

Analysis of the AE signals parameter at the critical area on the concrete beam

This paper enquires the utilization of acoustic emission (AE) to identify the nature of damage such as tensile cracks and shear movements at the critical zone within a structure. The AE parameters were involved in this research are Amplitude, Rise Time and Average Frequency. Some experimental works were performed with the scale of the beam (150 × 250 × 1900 mm) and AE data was captured then analyse by post-test analysis. Eventually, the acoustic emission analysis was successfully identifying the cracks movement accordance to the real observation during the loading cycle.