Achmad Syafiuddin

Silver Nanoparticles in the Water Environment in Malaysia: Inspection, characterization, removal, modeling, and future perspective

The current status of silver nanoparticles (AgNPs) in the water environment in Malaysia was examined and reported. For inspection, two rivers and two sewage treatment plants (STPs) were selected. Two activated carbons derived from oil palm (ACfOPS) and coconut (ACfCS) shells were proposed as the adsorbent to remove AgNPs. It was found that the concentrations of AgNPs in the rivers and STPs are in the ranges of 0.13 to 10.16 mg L−1 and 0.13 to 20.02 mg L−1, respectively, with the highest concentration measured in July. ACfOPS and ACfCS removed up to 99.6 and 99.9% of AgNPs, respectively, from the water. The interaction mechanism between AgNPs and the activated carbon surface employed in this work was mainly the electrostatic force interaction via binding Ag+ with O− presented in the activated carbon to form AgO. Fifteen kinetic models were compared statistically to describe the removal of AgNPs. It was found that the experimental adsorption data can be best described using the mixed 1,2-order model. Therefore, this model has the potential to be a candidate for a general model to describe AgNPs adsorption using numerous materials, its validation of which has been confirmed with other material data from previous works.

Application of the kinetic and isotherm models for better understanding of the behaviors of silver nanoparticles adsorption onto different adsorbents

It is the first time to do investigation the reliability and validity of thirty kinetic and isotherm models for describing the behaviors of adsorption of silver nanoparticles (AgNPs) onto different adsorbents. The purpose of this study is therefore to assess the most reliable models for the adsorption of AgNPs onto feasibility of an adsorbent. The fifteen kinetic models and fifteen isotherm models were used to test secondary data of AgNPs adsorption collected from the various data sources. The rankings of arithmetic mean were estimated based on the six statistical analysis methods of using a dedicated software of the MATLAB Optimization Toolbox with a least square curve fitting function. The use of fractal-like mixed 1, 2-order model for describing the adsorption kinetics and that of Fritz-Schlunder and Baudu models for describing the adsorption isotherms can be recommended as the most reliable models for AgNPs adsorption onto the natural and synthetic adsorbent materials. The application of thirty models have been identified for the adsorption of AgNPs to clarify the usefulness of both groups of the kinetic and isotherm equations in the rank order of the levels of accuracy, and this significantly contributes to understandability and usability of the proper models and makes to knowledge beyond the existing literatures.

Comparison of Cost Benefits of New Installation and Retrofitted Rainwater Harvesting Systems for Commercial Buildings

This paper aims to evaluate cost benefits of new installation and retrofitted rainwater harvesting system (RWHS) for commercial building. The selected commercial building is AEON Taman Universiti, Johor, Malaysia. Daily rainfall data were obtained from the Senai International Airport station. The mass balance model was adopted for the simulation approach. Several economic parameters, namely, net present value (NPV), return on investment (ROI), and benefit-cost ratio (BCR) are used for the evaluation. Maximum NPV, BCR, and ROI of the new installation RWHS are 1.9, 1.5, and 5.5 times higher, respectively, than those of the retrofitted RWHS. It is concluded that new installation RWHS provides more economic benefits compared to the retrofitted RWHS.

Performance of small and large scales rainwater harvesting systems in commercial buildings under different reliability and future water tariff scenarios

A rainwater harvesting system (RWHS) was proposed for small and large commercial buildings in Malaysia as an alternative water supply for non-potable water consumption. The selected small and large commercial buildings are AEON Taman Universiti and AEON Bukit Indah, respectively. Daily rainfall data employed in this work were obtained from the nearest rainfall station at Senai International Airport, which has the longest and reliable rainfall record (29 years). Water consumption at both buildings were monitored daily and combined with the secondary data obtained from the AEONs offices. The mass balance model was adopted as the simulation approach. In addition, the economic benefits of RWHS in terms of percentage of reliability (R), net present value (NPV), return on investment (ROI), benefit-cost ratio (BCR), and payback period (PBP) were examined. Effects of rainwater tank sizes and water tariffs on the economic indicators were also evaluated. The results revealed that the percentages of reliability of the RWHS for the small and large commercial buildings were up to 93 and 100%, respectively, depending on the size of rainwater tank use. The economic benefits of the proposed RWHS were highly influenced by the tank size and water tariff. At different water tariffs between RM3.0/m3 and RM4.7/m3, the optimum PBPs for small system range from 6.5 to 10.0 years whereas for the large system from 3.0 to 4.5 years. Interestingly, the large commercial RWHS offers better NPV, ROI, BCR, and PBP compared to the small system, suggesting more economic benefits for the larger system.

Novel Weed-Extracted Silver Nanoparticles and Their Antibacterial Appraisal against a Rare Bacterium from River and Sewage Treatment Plan

This is the first investigation to demonstrate the use of biochemical contents present within Cyperus rotundus, Eleusin indica, Euphorbia hirta, Melastoma malabathricum, Clidemia hirta and Pachyrhizus erosus extracts for the reduction of silver ion to silver nanoparticles (AgNPs) form. In addition, the antibacterial capability of the synthesized AgNPs and plant extracts alone against a rare bacterium, Chromobacterium haemolyticum (C. haemolyticum), was examined. Moreover, ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX) and inductively coupled plasma atomic emission spectroscopy (ICPOES) of the synthesized AgNPs were characterized. The smallest AgNPs can be produced when Cyperus rotundus extracts were utilized. In addition, this study has found that the synthesis efficiencies using all plant extracts are in the range of 72% to 91% with the highest percentage achieved when Eleusin indica extract was employed. All synthesized AgNPs have antibacterial capability against all examined bacteria depending on their size and bacteria types. Interestingly, Melastoma malabathricum and Clidemia hirta extracts have demonstrated an antibacterial ability against C. haemolyticum.

Biocomposites Formulated with Virgin/Recycled Acrylonitrile Butadiene Styrene

This study aims to examine mechanical properties of biocomposites formulated with virgin/recycled acrylonitrile butadiene styrene (ABS). Neat virgin ABS (VABS), neat recycled ABS (RABS), VABS with 15% palm long fiber (VABS/15PLF), and RABS with 10% palm short fiber (RABS/10PLF) were fabricated and examined. Twin extruder machine was used to manufacture granular composite. Impact, tensile, and hardness tests were carried out. This study found that the incorporating palm fiber into the matrix polymer increased brittleness of the composites. Impact strength of the composites increases with the rise filler loadings. Increasing filler loading in VABS was found to be able to increase the composite hardness. Conversely, for RABS, the composite hardness was found to decrease with the rise filler loadings.

Evaluation of empirical radar rainfall model during the massive flood in Malaysia

Accurate rainfall estimation from radar reflectivity is crucial in hydrological modeling and quantitative precipitation estimation. Various rainfall intensities exhibited by different rainfall drop size distribution contribute to reflectivity and rain rate relationship (Z-R) variability in radar rainfall estimation. This paper focuses to evaluate the Z-R model during the massive flood in December 2014 for different rainfall intensity. Hourly reflectivity and rain gauge data were used. Linear and non-linear least square regression were applied to compare the accuracy of Z-R coefficients (a and b). This study found that the non-linear least square gives the best evaluation of a and b estimates in high intensity rainfall and Kelantan was experiencing frequent high intensity rainfall during the massive flood in December 2014. Evaluation of empirical model demonstrated in this study can improve the accuracy of radar rainfall estimation.

Simple Model for Simulating Characteristics of River Flow Velocity in Large Scale

We propose a simple computer based phenomenological model to simulate the characteristics of river flow velocity in large scale. We use shuttle radar tomography mission based digital elevation model in grid form to define the terrain of catchment area. The model relies on mass-momentum conservation law and modified equation of motion of falling body in inclined plane. We assume inelastic collision occurs at every junction of two river branches to describe the dynamics of merged flow velocity.