Alias Mohd Yusof

Removal of Cr(VI) and As(V) from aqueous solutions by HDTMA-modified zeolite Y.

The synthesized zeolite NaY from rice husk ash (RHA) and the commercial zeolite NaY both modified with surfactants in amounts equal to 50%, 100% and 200% of their external cation exchange capacity (ECEC) were used to remove chromate and arsenate anions from aqueous solutions. While the unmodified zeolite Y had little or no affinity for the Cr(VI) and As(V) anionic species, the surfactant-modified zeolite Y (SMZY) showed significant ability to remove of these anions from the aqueous solutions. The highest chromates and arsenates adsorption efficiency was observed from solutions of pH values 3 and 8, respectively because of the dominance of the univalent species of both anions. The adsorption equilibrium data were best fitted with the Langmuir isotherm model with the highest removal capacities observed for the SMZY initially prepared considering the hexadecyltrimethyl ammonium (HDTMA) amount equal to the 100% of the ECEC of zeolite Y. Synthesized SMZY remove Cr(VI) and As(V) more than the corresponding commercial one due to its lower silica to alumina ratio. Thus, the HDTMA-covered modified zeolite Y synthesized using RHA can be used to remove Cr(VI) and As(V) from water.

Kinetic and equilibrium studies of the removal of ammonium ions from aqueous solution by rice husk ash-synthesized zeolite Y and powdered and granulated forms of mordenite.

The removal of ammonium from aqueous solutions using zeolite NaY prepared from a local agricultural waste, rice husk ash waste was investigated and a naturally occurring zeolite mordenite in powdered and granulated forms was used as comparison. Zeolite NaY and mordenite were well characterized by powder X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis and the total cation exchange capacity (CEC). CEC of the zeolites were measured as 3.15, 1.46 and 1.34 meq g(-1) for zeolite Y, powdered mordenite and granular mordenite, respectively. Adsorption kinetics and equilibrium data for the removal of NH(4)(+) ions were examined by fitting the experimental data to various models. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The equilibrium pattern fits well with the Langmuir isotherm compared to the other isotherms. The monolayer adsorption capacity for zeolite Y (42.37 mg/g) was found to be higher than that powdered mordenite (15.13 mg/g) and granular mordenite (14.56 mg/g). Thus, it can be concluded that the low cost and economical rice husk ash-synthesized zeolite NaY could be a better sorbent for ammonium removal due to its rapid adsorption rate and higher adsorption capacity compared to natural mordenite.

Removal of Heavy Metal Ions with Acid Activated Carbons Derived from Oil Palm and Coconut Shells

In this work, batch adsorption experiments were carried out to investigate the suitability of prepared acid activated carbons in removing heavy metal ions such as nickel(II), lead(II) and chromium(VI). Acid activated carbons were obtained from oil palm and coconut shells using phosphoric acid under similar activation process while the differences lie either in impregnation condition or in both pretreatment and impregnation conditions. Prepared activated carbons were modified by dispersing hydrated iron oxide. The adsorption equilibrium data for nickel(II) and lead(II) were obtained from adsorption by the prepared and commercial activated carbons. Langmuir and Freundlich models fit the data well. Prepared activated carbons showed higher adsorption capacity for nickel(II) and lead(II). The removal of chromium(VI) was studied by the prepared acid activated, modified and commercial activated carbons at different pH. The isotherms studies reveal that the prepared activated carbon performs better in low concentration region while the commercial ones in the high concentration region. Thus, a complete adsorption is expected in low concentration by the prepared activated carbon. The kinetics data for Ni(II), Pb(II) and Cr(VI) by the best selected activated carbon fitted very well to the pseudo-second-order kinetic model.

ENVIRONMENTAL ASSESSMENT OF COASTAL SEDIMENTS BY THE ELEMENTAL RATIOING TECHNIQUE

The distribution of heavy and trace elements in coastal sediments was obtained by elemental analysis techniques such as INAA and GFAAS. The elemental concentrations were expressed in terms of enrichment factors derived by the elemental ratioing method, and evaluation was done by comparison to those found in SRMs. The associated sources of polluting elements were traced from their distribution patterns and, where applicable, related to the surrounding activities. Sample to sample variation was also taken into account to establish any correlative factors.

Speciation of Se(IV) in marine sediments using neutron activation analysis after co-precipitation with dibenzyldithiocarbamate (DBDTC) with phenolphthalein

The determination of Se(IV) forms in marine sediments was performed on core samples taken from a fairly polluted environment. Sediment core samples were sliced into strata of between 2 and 3 cm thickness, dried at 60°C for 2 weeks and ground to<200 mesh size prior to the analysis. The powdered samples were dissolved by microwave digestion using a MDS-81D Microwave Digestion System. The quantitative determination of Se(IV) was done by co-precipitating the Se(IV) dibenzyldithiocarbamate complex with phenolphthalein (DBDTC-Pp) followed by irradiation of the Se(IV) forms in a neutron flux of 4×1012 neutrons cm−2 s−1 from a TRIGA Mk.II reactor at the Malaysian Institute of Nuclear Technology and Research (MINT). The Se(IV) species concentrations were calculated using the 136.0 keV γ-rays of the 75Se by the comparison method. Standard reference materials, such as SL-7 SRM supplied by IAEA was used to provide good quality assurance control. The results showed that the concentrations of Se(IV) in the sediment samples are between 3.93±0.05 ng g−1 and approximately 50.17±0.08 ng g−1. In general it was found that the distribution of Se(IV) concentrations along the South Johore coastal area showed some variations with locations and strata.

Removal of Ca2+ and Zn2+ from aqueous solutions by zeolites NaP and KP

Zeolites P in sodium (NaP) and potassium (KP) forms were used as adsorbents for the removal of calcium (Ca2+) and zinc (Zn2+) cations from aqueous solutions. Zeolite KP was prepared by ion exchange of K+ with Na+ which neutralizes the negative charge of the zeolite P framework structure. The ion exchange capacity of K+ on zeolite NaP was determined through the Freundlich isotherm equilibrium study. Characterization of zeolite KP was determined using infrared spectroscopy and X‐ray diffraction (XRD) techniques. From the characterization, the structure of zeolite KP was found to remain stable after the ion exchange process. Zeolites KP and NaP were used for the removal of Ca and Zn from solution. The amount of Ca2+ and Zn2+ in aqueous solution before and after the adsorption by zeolites was analysed using the flame atomic absorption spectroscopy method. The removal of Ca2+ and Zn2+ followed the Freundlich isotherm rather than the Langmuir isotherm model. This result also revealed that zeolite KP adsorbs Ca2+ and Zn2+ more than zeolite NaP and proved that modification of zeolite NaP with potassium leads to an increase in the adsorption efficiency of the zeolite. Therefore, the zeolites NaP and KP can be used for water softening (Ca removal) and reducing water pollution/toxicity (Zn removal).

Marine sediments analysis by the elemental ratioing technique

Abstract A study on the evaluation of pollution trends in marine core sediments taken in the vicinity of an industrial zone was attempted by analyzing trace elements such as As, Ce, Cr, Dy, Eu, La, Lu, Mn, Sb, Sc, Sm, Th, U, V and Yb using neutron activation analysis. The elemental concentrations were expressed in terms of enrichment factors (EF) obtained by the elemental ratioing technique using scandium as the reference element. The quantitative distribution and assessment on the extent of pollution by some of the elements were done by comparing their EFs to those found in reference materials. The general elemental distribution was presented on maps and any abnormalities in the distribution pattern found were deduced with reference to their point sources.

The use of multi-walled carbon nanotubes as possible carrier in drug delivery system for aspirin

Carbon nanotubes (CNTs) have raised great interest in a number of applications, including field emission, energy storage, molecular electronics, sensors, biochips and drug delivery systems. This is due to their remarkable mechanical properties, chemical stability and biofunctionalizability. This nanomaterial is low in weight, has high strength and a high aspect ratio (long length compared to a small diameter). This paper will present a brief overview of drugs adsorbed onto the surface of carbon nanotubes via sonication method. The surface area of carbon nanotubes was measured by methylene blue method, Carbon nanotubes synthesized by catalytic chemical vapor deposition (CCVD) method were purified and functionalized in a mixture of concentrated acids (H2SO4:HNO3 = 3:1) at room temperature (25° C) via sonication in water bath, yielding carboxylic acid group on the CNTs’ surface. CNT was successfully loaded with 48 %(w/w) aspirin molecules by suspending CNTs in a solution of aspirin in alcohol. Analysis of lo...

The use of charcoal from agriculture waste in the speciation of iodine from well and river waters

The concentrations of iodine in fresh waters are known to be within the range of 0.5 to 35 ng·ml−1, much lower than in oceanic waters. The iodine concentrations, particularly that of129I which is significant from the radiation safety aspect, in public drinking waters have to be specified in order to verify the required level before distribution for domestic use. A modified version of an established method was used in the adsorption of iodine, iodate, total inorganic iodine and charcoal-adsorbable iodine using activated carbon prepared from oil palm kernel wastes. A thorough investigation of the physical properties of the activated carbon was carried out to determine its viability as an adsorbent for volatile species such as iodine. The iodine species were preconcentrated from water samples collected from wells in villages and from water intake points along rivers. The quantitative analysis of the species adsorbed was done by irradiating the activated charcoal loaded with the respective species in a neutron flux of 5.1·1012 n·cm−2·s−1 from a TRIGA MkII, nuclear reactor. Recovery experiments using spiked samples was done to provide quality assurance controls.

Synthesis and Structural Properties of Nanoselenium-Supported MCM-41 Material

The authors describe herein a new process for the synthesis of nanoselenium–supported MCM-41 hybrid material. Selenium nanoparticles were synthesized via chemical reduction method that this method is capable of producing spherical selenium nanoparticles of size 20 to 80 nm, under ambient conditions, and covalently bonded to MCM-41 framework by 3-(triethoxysilyl)-propylamine (APTES). The structures, morphology and size of the products were investigated by several characterization techniques such as XRD, SEM, TEM, FT-IR, UV–vis/DRS, Raman spectroscopy, and N2 adsorption–desorption isotherms method. These results demonstrated that Se-MCM-41 is a promising candidate for biosensor, adsorbent, or catalyst.