Megat Ahmad Kamal Megat Hanafiah

Adsorption of humic acid from aqueous solutions on crosslinked chitosan–epichlorohydrin beads: Kinetics and isotherm studies

The adsorption of humic acid on crosslinked chitosan-epichlorohydrin (chitosan-ECH) beads was investigated. Chitosan-ECH beads were characterized by Fourier transform infrared spectroscopy (FTIR), surface area and pore size analyses, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out and optimum humic acid adsorption on chitosan-ECH beads occurred at pH 6.0, agitation rate of 300 rpm and contact time of 50 min. Adsorption equilibrium isotherms were analyzed by Langmuir and Freundlich models. Freundlich model was found to show the best fit for experimental data while the maximum adsorption capacity determined from Langmuir model was 44.84 mg g(-1). The adsorption of humic acid on chitosan-ECH beads was best described with pseudo-first-order kinetic model. For desorption study, more than 60% of humic acid could be desorbed from the adsorbent using 1.0M HCl for 180 min.

Biosorption of copper ions from dilute aqueous solutions on base treated rubber (Hevea brasiliensis) leaves powder: kinetics, isotherm, and biosorption mechanisms

The efficiency of sodium hydroxide treated rubber (Hevea brasiliensis) leaves powder (NHBL) for removing copper ions from aqueous solutions has been investigated. The effects of physicochemical parameters on biosorption capacities such as stirring speed, pH, biosorbent dose, initial concentrations of copper, and ionic strength were studied. The biosorption capacities of NHBL increased with increase in pH, stirring speed and copper concentration but decreased with increase in biosorbent dose and ionic strength. The isotherm study indicated that NHBL fitted well with Langmuir model compared to Freundlich and Dubinin-Radushkevich models. The maximum biosorption capacity determined from Langmuir isotherm was 14.97 mg/g at 27 degrees C. The kinetic study revealed that pseudosecond order model fitted well the kinetic data, while Boyd kinetic model indicated that film diffusion was the main rate determining step in biosorption process. Based on surface area analysis, NHBL has low surface area and categorized as macroporous. Fourier transform infrared (FT-IR) analyses revealed that hydroxyl, carboxyl, and amino are the main functional groups involved in the binding of copper ions. Complexation was one of the main mechanisms for the removal of copper ions as indicated by FT-IR spectra. Ion exchange was another possible mechanism since the ratio of adsorbed cations (Cu2+ and H+) to the released cations (Na+, Ca2+, and Mg2+) from NHBL was almost unity. Copper ions bound on NHBL were able to be desorbed at > 99% using 0.05 mol/L HCl, 0.01 mol/L HNO3, and 0.01 mol/L EDTA solutions.

Acid blue 25 adsorption on base treated Shorea dasyphylla sawdust: kinetic, isotherm, thermodynamic and spectroscopic analysis.

The potential of base treated Shorea dasyphylla (BTSD) sawdust for Acid Blue 25 (AB 25) adsorption was investigated in a batch adsorption process. Various physiochemical parameters such as pH, stirring rate, dosage, concentration, contact time and temperature were studied. The adsorbent was characterized with Fourier transform infrared spectrophotometer, scanning electron microscope and Brunauer, Emmett and Teller analysis. The optimum conditions for AB 25 adsorption were pH 2, stirring rate 500 r/min, adsorbent dosage 0.10 g and contact time 60 min. The pseudo second-order model showed the best conformity to the kinetic data. The equilibrium adsorption of AB 25 was described by Freundlich and Langmuir, with the latter found to agree well with the isotherm model. The maximum monolayer adsorption capacity of BTSD was 24.39 mg/g at 300 K, estimated from the Langmuir model. Thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were determined. It was found that AB 25 adsorption was spontaneous and exothermic.

Kinetics and Isotherm Studies on Nd(III) Adsorption onto Xanthated Chitosan

Xanthated chitosan (XC) beads synthesized from the reaction between sulphur and hydroxyl groups were applied to adsorb rare earth metal ion, Nd (III). Adsorption of Nd (III) was found to be a function of pH of initial solution, adsorbent dosage and contact time. The optimum conditions for Nd (III) adsorption were at pH 3 and adsorbent dosage of 0.02 g. Rapid adsorption process was observed as it took only 10 min for reaching the equilibrium state. Chemisorption was identified as the rate limiting step and the kinetics data correlated well with the pseudo-second-order model.

Adsorption behavior of Pb(II) onto xanthated rubber (Hevea brasiliensis) leaf powder

Adsorption behavior of Pb(II) onto xanthated rubber (Hevea brasiliensis) leaf powder A plant waste, rubber (Hevea brasiliensis) leaf powder was modified with carbon disulfide (xanthation) for the purpose of introducing sulfur groups, and the adsorbent performance in removing Pb(II) ion was evaluated. Pb(II) adsorption was confirmed by spectroscopic analysis, which involved Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The amount of Pb(II) adsorbed increased with increasing pH, contact time and concentration but slightly decreased with increasing ionic strength. Adsorption equilibrium was achieved in less than 60 min and followed the pseudo-second order model. The isotherm data indicated that Pb(II) adsorption on xanthated rubber leaf (XRL) fitted well with Langmuir isotherm model. The maximum adsorption capacity computed from the Langmuir isotherm model was 166.7 mg/g. Pb(II) adsorption occurred via ion-exchange and complexation mechanisms.

Variable filtered photographic film as a radiation detector for environmental radiation monitoring

Environmental radiation is an ionising radiation that present in the natural environment which mostly originates from cosmic rays and radionuclide agents in the environment. This may lead the population to be exposed to the radiation. Therefore, the environmental radiation needs to be observed cautiously to minimize the impact of radiation. However, there is no specific or proper monitoring device that provides an outdoor environmental radiation monitoring. Hence, a new outdoor environmental radiation monitoring device was developed. A photographic film has been chosen as a dosimeter. The purpose of this study was to prove the covered photographic film attached with variable filter can be used to develop environmental radiation monitoring device to detect the ionising radiation. The filter used was variable thickness of plastic, aluminium (Al) and lead (Pb). The result from the study showed that the mean optical density (OD) values for medium speed film are in the range 0.41 to 0.73, and for fast speed film the OD values are in the range 0.51 to 1.35. The OD values decreased when the filter was attached. This has proven that the photographic film can be used to detect radiation and fast speed film was more sensitive compared to medium speed film.

Cogon Grass for Oil Sorption: Characterization and Sorption Studies

Cogon grass (Imperata cylindrica), an invasive, unwanted grass was used and evaluated for its applicability for the sorption of engine oil. Other than dried and ground for smaller size, no notable treatment was performed on the cogon grass. The physical and chemical properties of cogon grass were characterized by ash content, bulk density, pH slurry, and Field Emission Scanning Electron Microscopy (FESEM). The oil sorption was performed in a batch adsorption system. The effects of contact time, dosage of adsorbent and oil retention were investigated. The bulk density and ash content of the prepared carbon was 0.34 g/ml and 7.80 %, respectively. The pH slurry value was near neutrality (6.48). FESEM micrograph of cogon grass showed jagged and rough surface. FTIR spectra revealed the presence of aromatic rings of lignin and some aromatic compounds associated with CH. Carbon, hydrogen and nitrogen (CHN) analysis revealed that 41% of cogon grass consists of carbon. The cogon grass was observed to wet oil almost instantly with sorption equilibrium time of 5 min. The dose of cogon grass was found to slightly affect the sorption capacity. Oil retention experiments reveal the good ability of cogon grass to hold oil with about 96% retention after 24 h dripping. This study may provide an insight on the usefulness of cogon grass for removal of engine oils.

Adsorption of Cu(II) onto Cross-Linked Chitosan Coated Bentonite Beads: Kinetic and Isotherm Studies

In this study, cross-linked chitosan coated bentonite (CCB) beads were prepared as a potential adsorbent to adsorb Cu(II) from aqueous solution. As adsorption capacity was affected by several conditions such as initial Cu(II) concentrations, stirring period and temperature, these parameters were important to be investigated. Three different concentrations of Cu(II) were used in the kinetic study, which were 10, 25 and 50 mg/L. The experimental data was found fitted well with the pseudo-second-order model, an indication that chemisorption was the rate controlling mechanism. Isotherm study was done at different temperatures with concentration of Cu(II) was varied from 10 to 200 mg/L. The maximum monolayer adsorption of Cu(II) on CCB beads based on Langmuir isotherm model at 300, 310 and 320 K were 114.94, 119.05 and 77.52 mg/g, respectively. Therefore, adsorption of Cu(II) was preferred at lower temperatures. This work proved CCB beads as an effective adsorbent for fast removal of Cu(II) from wastewater solutions.

Methylene Blue Adsorption onto NaOH Treated Leucaena leucocephala Leaf Power

The potential of sodium hydroxide (NaOH) modified Petai Belalang (Leucaenaleucocephala) leaf powder as a biosorbent for methylene blue removal from aqueous solutions was investigated. Adsorption parameters studied include initial dye concentration, pH, dosage, kinetics and isotherms. The pHzpc of chemically treated Leucaenaleucocephala leaf powder was 7.50 and adsorption equilibrium time was achieved after 60 min. The kinetic data was best represented by the pseudo-second order model. The maximum adsorption capacity predicted from Langmuir model was 208.33 mg g-1. This work indicated that NaOH treated Leucaenaleucocephala leaf powder can be an attractive biosorbent for MB removal from diluted industrial wastewater.

Effect of Physicochemical Parameters on Methylene Blue Adsorption by Sulfuric Acid Treated Spent Grated Coconut

The effect of physicochemical parameters on methylene blue (MB) adsorption by sulfuric acid treated spent grated coconut (SSGC) was investigated. The field emission scanning electron microscope (FESEM) images showed a change in surface morphology of spent grated coconut before and after acid treatment. Energy dispersive X-ray (EDX) spectrometer suggested the mechanism of ion-exchange occurred during MB adsorption onto SSGC. The pHpzc value of SSGC was 5.40. The amount of MB adsorbed remained constant after pH 3. The optimum dosage of SSGC was observed at 0.03 g, while the stirring rate did not significantly affect the amount of MB adsorbed. This work suggested electrostatic attraction and ion-exchange as the main mechanisms involved in MB adsorption.