Muhammad Abbas Ahmad Zaini

Adsorption of heavy metals onto activated carbons derived from polyacrylonitrile fiber

The aim of this research is to produce activated carbons derived from polyacrylonitrile (PAN) fiber and to examine their feasibility of removing heavy metals from aqueous solution. Thermogravimetric analysis was used to identify the suitable conditions for preparing oxidized fiber and coke as activated carbon precursors. Steam and CO(2) were used to activate the precursors. Activated carbons were characterized by their pore texture, elemental compositions and surface functionalities. Batch adsorption and desorption studies were carried out to determine the metal-binding ability of activated carbons. Two commercial activated carbon fibers (ACFs), i.e., A-20 and W10-W, were employed to compare the removal performance of PAN derived activated carbons. Influence of oxidation treatment of PAN fiber prior to steam activation was also explored and discussed. Results indicated that steam produced a higher surface area but a lower resultant yield as compared to CO(2). Also, precursors activated by steam showed a greater removal performance. For both activation methods, fiber displayed a better metal-binding ability than coke. A small nitrogen loss from PAN fiber as a result of oxidation treatment assisted a greater removal of Cu(II) and Pb(II), but the interaction to Cu(II) was found stronger. It is proposed that the formation of cyclized structure by oxidation treatment minimized the nitrogen loss during steam activation, hence increased the uptake performance.

Adsorption of aqueous metal ions on cattle-manure-compost based activated carbons.

The objective of this study is to examine the suitability and performance of cattle-manure-compost (CMC) based activated carbons in removing heavy metal ions from aqueous solution. The influence of ZnCl(2) activation ratios and solution pH on the removal of Cu(II) and Pb(II) were studied. Pore texture, available surface functional groups, pH of point zero charge (pH(PZC)), thermogravimetric analysis and elemental compositions were obtained to characterize the activated carbons. Batch adsorption technique was used to determine the metal-binding ability of activated carbons. The equilibrium data were characterized using Langmuir, Freundlich and Redlich-Peterson models. It was found that the uptake of aqueous metal ions by activated carbons could be well described by Langmuir equation. It is suggested that the increase of surface area and mesopore ratio as a result of increasing activation ratios favored the removal of Cu(II), while activated carbon rich in acidic groups showed selective adsorption towards Pb(II). The preferable removal of Cu(II) over Pb(II) could be due to the rich nitrogen content as well as the higher mesoporous surface area in the CMC activated carbons. The impregnated CMC activated carbons also showed a better performance for Cu(II) removal at varying solution pH than Filtrasorb 400 (F400), while a similar performance was observed for Pb(II) removal.

Potassium hydroxide activation of activated carbon: a commentary

Copyright

A comparative study of various oil extraction techniques from plants

Abstract Researchers have shown that techniques such as microwave-assisted extraction, ultrasound-assisted extraction, pressurized liquid extraction, and supercritical fluid extraction developed for extraction of valuable components from plants and seed materials have been successfully used to effectively reduce the major shortcomings of the traditional method such as Soxhlet extraction. These include shorter extraction time, increase in yield of extracted components, decrease in solvent consumption, and improvement of the quality of extracts. This review presents a detailed description of the principles and mechanisms of the various extraction techniques for better understanding and summarizes the potential of these techniques in the extraction of oil from plants and seed materials. Discussions on some of the parameters affecting the extraction efficiency are also highlighted, with special emphasis on supercritical fluid extraction. A comparison of the performance of traditional Soxhlet extraction with that of other extraction techniques is also presented.

A REVIEW OF MIXED REVERSE MICELLE SYSTEM FOR ANTIBIOTIC RECOVERY

This article discusses the application of mixed reverse micelles in downstream processing of antibiotics. Purification and recovery processes for antibiotics in downstream processing are major expenses, about 70% of the total cost of production, giving them a significant impact on manufacturing cost. Moreover, there are a number of challenges and difficulties in the separation process requirements for antibiotics, since the mixture is quite complex, with broth, hazardous solvents, by-products, intermediate material, and impurities; in addition, antibiotics are easy to denature. Therefore, the development of effective separation techniques is required to produce high-purity of biomaterials. The use of reverse micelles is thought to be among the most promising due to the processs high selectivity and efficiency. Most studies on reverse micelle extraction technology have been performed by using anionic surfactant sodium bis (2-ethyl-1-hexyl) sulfosuccinate (AOT). However, the activities of antibiotics hosted in this type of surfactant have a significant effect due to the strong electrostatic and hydrophobic interaction between antibiotic and surfactant molecules. Due to these problems many alternatives have been developed recently, and reverse micelles have high potential in the purification of biomolecules. Therefore, this review discusses the ability of mixed ionic-nonionic reverse micelles to provide a safe microenvironment for antibiotics by maintaining the strength of attraction between the reverse micelle molecule and the antibiotic while avoiding the denaturation of the antibiotic. The article highlights the potential of mixed ionic-nonionic reverse micelle technology as a tool of antibiotic recovery from various mediums.

Adsorption properties of cationic rhodamine B dye onto metals chloride-activated castor bean residue carbons

This work was aimed to evaluate the feasibility of castor bean residue based activated carbons prepared through metals chloride activation. The activated carbons were characterized for textural properties and surface chemistry, and the adsorption data of rhodamine B were established to investigate the removal performance. Zinc chloride-activated carbon with specific surface area of 395 m2/g displayed a higher adsorption capacity of 175 mg/g. Magnesium chloride and iron(III) chloride are less toxic and promising agents for composite chemical activation. The adsorption data obeyed Langmuir isotherm and pseudo-second-order kinetics model. The rate-limiting step in the adsorption of rhodamine B is film diffusion. The positive values of enthalpy and entropy indicate that the adsorption is endothermic and spontaneous at high temperature.

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.

Physicochemical characteristics of surface modified Dijah-Monkin bentonite

ABSTRACT The aim of this study was the evaluation of the physicochemical characteristics of surface modified Dijah-Monkin bentonite clay. The clay was modified by calcination and treatment with hydrochloric acid. The natural and modified clays were characterized by x-ray fluorescence (XRF), Fourier transform infrared (FTIR), x-ray diffraction (XRD), electron dispersive x-ray (EDX), thermogravimetric analysis (TG), scanning electron microscopy (SEM), elemental composition, cation exchange capacity (CEC), Brunauer–Emmett–Teller (BET) specific surface area and methylene blue adsorption. The XRF displayed the presence of SiO2 and Al2O3 in the range of 61.6–65.6 wt% and 19.4–21.7 wt%, respectively. The FTIR spectra showed the existence of Al–OH, Al–O, Si–O, and Si–O–Si functional groups in all clay samples, confirming the presence of hydrated aluminosilicate in the clay. The BET surface area decreased from 23.5 to 17.1 m2/g after acid treatment, while the CEC of clay samples range between 40.7 and 20.2 mEq/100 g. The minerals present in clays are montmorillonite, quartz, kaolinite, and muscouvite. The maximum methylene blue adsorption were estimated as 59, 48, and 45.8 mg/g for natural, calcined, and acidified bentonite, respectively. The structural formula for one-layer unit of montmorillonite was determined as K0.722Ca0.155[Si7.686]iv[Al3.054Ti0.113]viO20(OH)4. The natural Dijah-Monkin bentonite is a promising adsorbent candidate for the removal of charged pollutants.

Insight into kinetics and thermodynamics properties of multicomponent lead(II), cadmium(II) and manganese(II) adsorption onto Dijah-Monkin bentonite clay

ABSTRACT Multicomponent adsorption of lead(II), cadmium(II) and manganese(II) by Nigerian Dijah-Monkin bentonite clay was investigated. The clay samples were characterized for elemental composition, cation exchange capacity and textural properties. Natural bentonite exhibits cation exchange capacity of 47.7 meq/100 g and specific surface area of 23.5 m2/g. Manganese(II) displays higher values of rate constant than lead(II) in multimetals adsorption. However, lead(II) is favorably adsorbed onto bentonite adsorbents at different concentrations studied. The multimetals adsorption onto bentonite clay samples is site selective and site specific. The pseudo-second-order kinetics model gave a better fit to the adsorption data, suggesting ion exchange and/or complex formation. The adsorption mechanism could be described by intraparticle diffusion with some restriction of metals diffusion due to film or boundary layer. Also, the multicomponent adsorption is endothermic and becomes more spontaneous as temperature increased from 303 to 338 K. Nigerian bentonite clay in its natural form is a promising adsorbent for multimetals removal in aqueous solution.

Enhanced lead(II) binding properties of heat-treated cattle-manure-compost-activated carbons

AbstractConsiderable concerns have been raised over the presence of lead(II) in water bodies. In this work, the performance of heat-treated cattle-manure-compost-activated carbons were investigated to remove lead(II) from aqueous solution. Activated carbons were prepared by one-step ZnCl2 activation followed by heat treatment at different temperatures. They were characterized according to BET surface area, pore size distribution, elemental analysis, pHPZC and Boehm’s titration. It was found that the increase of treatment temperature resulted in a decrease in both the BET surface area as well as the concentration of phenolic groups. However, such decreases were compensated by an increase of lead(II) by more than three times to a value of 0.110 mmol/g, and this was also true for commercial F400-activated carbon. Lead(II) adsorption onto heat-treated activated carbons could be described by Langmuir isotherm with weaker interaction to active sites. Results also suggested that the increase in lead(II) uptake w...