Characterization and thermal properties of chitosan/agar blends hydrogel membranes / Faiezah Hashim, Nor Hafizah Che Ismail and Mohd Lias Kamal

Continuous awareness of ecological problem has led to a paradigm shift on the use of biodegradable materials, especially from renewable agriculture feedstock and marine food processing industry wastes. Developments in the field of biomaterials have lead to significant advancements in the extraction of chitosan from local sources. Chitosan has been found in applications for biomedicine (wound dressings), tissue engineering (artificial skin), bone tissue engineering and one of the promising materials for preparing hydrophilic membranes and it has been widely studied. Most of the chitosan membranes so far have been fabricated using commercial chitosan. Nowadays, the main sources of chitosan are crab and shrimp shell. As the combination of properties of chitosan such as water binding capacity, fat binding capacity, bioactivity, biodegrability, and antifungal activity, chitosan and its modified analogs have shown many applications in medicine, cosmetics, agriculture, biochemical separation systems, tissue engineering, biomaterials and drug controlled release systems. However, chitosan also has some drawbacks, it being soluble in aqueous medium only in the presence of small amount of acid. Its mechanical properties have also proved to be unsuitable in some biomedical applications. In order to eliminate the disadvantageous, it can be modified by physical blending or/and chemical modification by grafting, interpenetrating polymer networks and crosslinking method. In this study, an attempt has been made to blend chitosan with other gelling material which is agar. Biopolymer from agar (polysaccharide) has received particular attention due to their natural origin, low cost and good compatibility. Since agar have good compatibility with most other polysaccharides and with proteins in near neutral conditions, blends of agar with chitosan may lead to the enhancement of the physical properties of chitosan membran

Adsorption process of heavy metals by low-cost adsorbent: a review

In this article, the potential of various low-cost adsorbents for the removal of heavy metals from contaminated water has been reviewed. Various conventional methods for heavy metal removal such as precipitation, evaporation, electroplating and also ion exchange have been applied since previous years. However, these methods have several disadvantages such as only limited to certain concentrations of metals ions, generation large amount of toxic sludge and the capital costs are much too high to be economical. Hence, adsorption using low-cost adsorbents is found to be more environmentally friendly. Adsorption is the alternative process, for heavy metal removal due to the wide number of natural materials or agricultural wastes gathering in abundance from our environment. High adsorption capacities, cost effectiveness and their abundance in nature are the important parameters which explain why the adsorbent is economical for heavy metal removal. In this review, a list of adsorbent literature has been compiled to provide a summary of available information on a wide range of low cost adsorbents for removing heavy metals from contaminated water. The application of available adsorption models such as the isotherm, kinetics and thermodynamics as well as the influence of parameters on metal adsorption by low cost adsorbent shall be reviewed to understand the adsorption mechanism of low-cost adsorbents

Antioxidant activity of different plant parts extracts of Dracaena umbratica Ridl

Medicinal plants contain phytochemicals which show various significant biological and pharmacological activities. In this study, the hexane, dichloromethane and methanol extracts from different parts (leaves, rhizomes and roots) of a local medicinal plant, Dracena umbratica, Ridl (Agavaceae) were evaluated for antioxidative activity using ferric thiocyanate (FTC) method and also DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging assay. The results showed that all the extracts exhibited weak radical scavenging activity and differ significantly from the standard antioxidants which are vitamin C and butylated hydroxytoluene (BHT). However results from the ferric thiocyanate (FTC) method showed that all the extracts except that of hexane and dichloromethane extracts of the rhizome of this plant possess high antioxidative property which was comparable to the standard reference, BHT. The antioxidative activity of these extracts did not differ significantly (P<0.5) from BHT. These results suggest that this plant species may have low content of radical scavenging compounds but can still be developed as potential antioxidant

A performance of hybrid biosorbent ‘M-Bios’ of Pb(II) and Cu(II) in aqueous solutions

‘M-bios’ biosorbent is a hybrid of mangrove wasted bark from charcoal industry at Perak, Malaysia and green algae from Sabah to remove heavy metals. This biosorbent is subjected to FTIR and ICP-MS. ‘M-Bios’ contain N – H (3421.89 cm-1, 3465.90 cm-1), C = O (1728.72 cm-1) and – OH (3531.37 cm-1, 3722.01 cm-1, 3768.36 cm-1) functional groups (weak groups) that that easily replaced by metal ions. The adsorption performances were fitted by pseudo-kinetic, Langmuir and Freundlich study. The plots obey both adsorption isotherm models, Langmuir and Freundlich by R2 values. A good agreement between experimental and theoretical qe for contact time data suggested that adsorption reaction happen in aqueous solution was a rate determination of chemisorption process(pseudo second-order kinetic)

Adsorption of Pb(II) ions by using Mangrove-Alginate Composite Beads (MACB): isotherm, kinetics & thermodynamics studies

Present study explored the potential of using mangrove-alginate composite bead (MACB) as adsorbent for the removal of Pb(II) ions from aqueous solution. The batch sorption was studied under different initial concentration (20 to 100 mg/L), contact time (5 to 210 min) and solution temperature (35 to 650C). The Langmuir, Freundlich, and Temkin isotherm models were used to analyze the experimental equilibrium data and isotherm constants. A comparison of kinetic models applied to the adsorption of Pb(II) ions on MACB beads was evaluated using pseudo-first order and pseudo-second order kinetics models. The experimental data were fitted well with the pseudo-second order kinetic model, means the mechanism of diffusion process is controlled by the adsorption reactions and not depend by the mass transfer during adsorption. Based on thermodynamics parameters, the results show that the adsorption capacity increases with an increase in temperature. The negative value of ΔHo (-1.402 kJ mol-1) and the decreasing kd value with increasing temperature, which indicate the sorption of Pb(II) onto MACB beads was feasible and an exothermic reaction. The positive value ΔSo(8.256 Jmol-1K-1) reflects good affinity of Pb(II) ions towards the MACB beads. The results described the potential for the MACB beads to be used as adsorbent for the removal of Pb(II) ions from wastewater

Comparative study on adsorption of PB(II) ions by alginate beads & mangrove-alginate composite beads

The aim of the present study report on the adsorption performance of alginate bead (AB) and mangrove-alginate composite bead (MACB) bead adsorbents for the removal of Pb(II) ions from aqueous solution. The effects of pH and initial concentration with contact time on the adsorption properties of Pb(II) onto both adsorbent were investigated and were described by isotherm and kinetic studies. The isotherm adsorption data were fitted well to Freundlich isotherms for both beads and the maximum adsorption capacities of the AB and MACB beads were 29.02 mg g-1 and 10.84 mg g-1, respectively. The kinetics adsorption data were best described to a pseudo-second-order kinetic models showing that the MACB beads had a higher kinetic adsorption rate at 2.6084 g mg-1 min-1 compared to AB at 0.7043 g mg-1 min-1

Removal of Iron (Fe) by adsorption using activated Carbon Moringa oleifera (ACMO) in aqueous solution / Nurul Zawani Alias et al.

Activated carbon has been widely developed as an adsorbent to adsorb heavy metal in wastewater due to its high efficiency and low cost. Activated carbon of Moringa oleifera (ACMO) was prepared from the woods for the removal of iron in aqueous solution. The ACMO was produced using chemical activation process impregnation with phosphoric acid as the activating agent. The surface morphology of ACMO was characterized using SEM, and the functional group present was determined using FTIR. Effects of various operating variables namely the carbon dose, adsorbate concentration and contact time on the removal of iron ions have been studied. The adsorption capacity was determined as a function of carbon doses (0.1, 0.2, 0.3, 0.4 and 0.5 g), adsorbate concentration (2, 4, 6, 8 and 10 mg/L) and the contact time between ACMO and aqueous solution (30, 60, 90 and 120 min) with constant parameters of temperature 303 K, agitation at 180 rpm and pH 8. From the data obtained, percent of moisture present in ACMO and raw M. oleifera (RMO) were 6.752% and 9.512% respectively. Meanwhile, amount of ash in ACMO was 1.451% and in RMO was 7.592%. In addition, the volatile matter present in ACMO was replaced from RMO about 28.431% and 23.715% respectively. The percentage of fixed carbon of ACMO and RMO were 63.366% and 59.181% respectively. The highest adsorption capacity obtained was at 8.043 mg/g with the amount of carbon dosage of 0.1 g, concentration of iron solution of 10 mg/L and contact time of 120 min

Development of novel adsorbent-mangrove-alginate composite bead (MACB) for removal of Pb(II) from aqueous solution

This study described a preparation of novel composite adsorbent for heavy metal removal by immobilized mangrove bark into alginate as supporting matrix. The removal of Pb(II) ions from aqueous solution by mangrove-alginate composite bead (MACB) was investigated by performing batch adsorption studies to evaluate the performances of the bead. It was found that the adsorption of Pb(II) ions by MACB beads was pH dependent, as the maximum percentage removal was obtained at pH 5.0. The results revealed the superior parameters of MACB beads had attained about 99.15% efficiency in conditions of 7 g L−1 MACB concentration, 150 min contact time, 5.0 as the initial pH, and 250 rpm agitation speed. The adsorption kinetic data can be well described using pseudo-second-order model and the equilibrium data were fitted well by Freundlich isothermal model, respectively. Thermodynamic parameters were calculated and revealed that the adsorption process is an exothermic and spontaneous reaction within range of temperature of 35–65 °C. This indicates that the MACB beads can be used as a promising adsorbent for removal of heavy metals from aqueous solutions