Papers by Keyword: Chemical Modification

Abstract: The desire to incorporate wood in modern construction has led to a considerable increase in the use of wood modification techniques, and especially thermal modification. However, thermally modified wood has poor performance against termites. The concept of using a combined chemical and thermal modification has been undertaken through the impregnation with either bicine or tricine prior to modification. This paper considers the effects of these chemicals on the activity of termites and considers their mode of action in terms of termite survival and on their effects on the symbiotic protists present within the termite gut.

Abstract: In this study, coconut shells were converted into biochar via pyrolysis and chemically modified via an acid-base treatment to enrich its adsorption capabilities. Batch experiments were carried out to analyze the adsorption potential of the modified coconut shell (MCSC) or removal of chromium, nickel, and copper from aqueous solution. The chemical modification increased the surface area of MCSC to 185.712 m²/g. Batch adsorption study using MCSC resulted in 99% removal of copper, 95% (nickel), and 39% (chromium). The adsorption of studied metal ions fitted well with Langmuir isotherm, showing a monolayer adsorption process. A kinetic analysis showed that all the samples match a strong correlation coefficient in pseudo-second-order (R²>0.95), indicating the occurrence of a chemical adsorption process.

Abstract: The use of agricultural by-products has been widely studied to develop effective and inexpensive adsorbent for heavy metal removal. In this study, sago (M.sagu) fly ash (FA) was chemically modified to afford an operational adsorbent for Pb (II) elimination from water. Chemical modification was carried out via acid-base treatment using NaOH and HCl. The chemically modified fly ash (MFA) was characterized via proximate, surface morphology, and functional groups' surface area analyses. The effects of adsorption parameters, namely, Pb (II) initial concentration, sorbent dosage and contact time on the eradication of Pb (II) by MFA was analyzed in batch experiments with Langmuir and Freundlich isotherms. Optimization of Pb (II) removal by MFA was studied via response surface methodology (RSM) approach. Results revealed that chemical modification has successfully enhanced the adsorptive properties of MFA (BET surface area: 231.4 m²/g, fixed carbon: 55.83%). MFA exhibits better Pb (II) removal efficiency (90.8%) compared to FA (63.6%) at the following adsorption condition: Pb (II) initial concentration (5 ppm), contact time (30 min) and agitation speed (150 rpm). The adsorption of Pb (II) by FA and MFA fitted well with Freundlich isotherm (R²>0.9). RSM study suggested that the optimum Pb (II) removal was 99.4% at the following conditions: Pb (II) initial concentration (20 ppm), contact time (2 h) and sorbent dosage (0.6 g/50 mL). The results concluded the potential optimum operational condition for Pb (II) removal from aqueous environment by MFA as a low cost adsorbent, at larger scale.

Abstract: In this study, carboxymethyl cellulose (CMC) used as matrix, while halloysite nanotube (HNT) used as nanofiller to produce bio-nanocomposite films via solvent casting method. The effect of sodium dodecyl sulfate (SDS) on tensile properties and morphology study of CMC/HNT bio-nanocomposite films have been investigated. The results showed that the mechanical properties of treated CMC/HNT bio-nanocomposite films using SDS enhanced the tensile strength, elongation at break and modulus of elasticity compared to untreated CMC/HNT bio-nanocomposites. Besides, the tensile fracture surface of treated bio-nanocomposites demonstrated by field emission scanning electron micrograph (FESEM) indicates that the presence of SDS improved the interfacial interaction between CMC matrix and treated HNT nanofiller.

Abstract: In this study, ground tire rubber (R-GTR) with the average particle size of 456 µm was chemically modified to produce modified ground tire rubber (M-GTR) that can work as ion exchange materials. The modification was performed by oxidation reaction. The ground tire rubber was oxidized at the range of temperature from 20 to 40^๐C for 48, 72 and 96 hours by a mixture of the HNO₃ /H₃PO₄/NaNO₂ system. The HNO₃/H₃PO₄ ratio was 1:3 and the concentration of NaNO₂ was 1.4% w/v. FT-IR revealed that the carboxyl group or the carbonyl group was successfully introduced into the modified ground tire rubber and SEM images demonstrated that the porosity of modified ground tire rubber increased. The results of the modified ground tire rubber showed that the carboxyl content increased with an increase of reaction time while %yield decreased with an increase of reaction time. The optimum condition for modification was the reaction at 30^๐C for 96 hours.

Abstract: Cocoa pod husk, an agricultural waste was chemically modified using Zinc Chloride (ZnCl₂) and used as an adsorbent for removal of acid dyes; (i) Acid Violet 17 (AV17) and (ii) Acid Yellow 36 (AY36) from aqueous solution. The raw (CPHC) and chemically modified cocoa pod husk carbon (ZCPHC) were characterized by Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray (EDX). The adsorption was performed on removing AV17 and AY36 from aqueous solution in batch adsorption system. The experimental data was simulated using Langmuir and Freundlich isotherm models. The isotherm study revealed that the AV17 adsorption on ZCPHC matched well with the Langmuir model, whereas AY36 adsorption on ZCPHC fitted well with Freundlich model. The maximum adsorption capacity determined from the Langmuir isotherm was 11.02 mg/g and 11.37 mg/g for AV17 and AY36 respectively at room temperature.

Abstract: The removal of lead from aqueous solutions was studied using the liquid-solid extraction method. The solids used are the crude phosphocalcic hydroxapatite [Ca₁₀(PO₄)₆(OH)₂] (HAPc), and phosphocalcic hydroxapatite treated with 5 % lactic acid solution (HAPal). The extraction results showed the influence of the initial concentration of Pb (II) and temperature of the suspensions. The maximum adsorption capacities of each material (HAPc and HAPal) were obtained with the application of Langmuir adsorption model. The most important quantity was founded as 41,84mg/g for HAPal. Isotherms established at different temperatures showed that this parameter affects greatly the adsorption of Pb (II) on both adsorbents. The best results were obtained at room temperature (25°C) compared with those recorded at 50°C.Finally, the results of this study allow us to note that the hydroxiapatite material can be as good extractant solid, for heavy metals, especially when it is modified with lactic acid.

Abstract: Water in liquid and gaseous form is the main factor which significantly affects degradation processes in the wood. The mechanism and rate of wooden degradation processes can be effectively influenced by appropriate methods and technologies for its protection. However new knowledge, based on the possibilities of application of modern physical and chemical analytical methods, confirms that most well-known and previously commonly used protective equipment damages wooden structure. Many chemical substances, which are included in preservatives such as organic and inorganic biocides, or also flame retardants, are declared to be environmentally unacceptable. Nowadays, environmentally friendly treatment technologies of wood have increased attention to the above reasons. Wooden treatment by silicones ranks among the technologies which repellent, fire resistant and corrosion effectiveness is demonstrated by many authors. This article presents results of the experimental study that deals with the mechanical properties of bonded joints in the wood treated by silicones.

Abstract: A novel chitosan derivative was prepared through direct reaction of pure chitosan with acetylacetone in the absence of a solvent, and it was characterized by elemental analysis, Fourier transform infrared spectrometry (FTIR), and ¹³C Nuclear Magnetic Ressonance (NMR) spectroscopy. Moreover, the antibacterial properties of the new biomaterial were tested by the direct contact method against multi-drug resistant strains of Staphylococcus aureus and Escherichia coli. The results from the characterization were consistent with the modification of the chemical structure made. The new derivative showed a better antibacterial activity than raw chitosan against E. coli strains, indicating that incorporation of imine link (Schiff base) enhanced its antibacterial activity against Gram-negative bacterium. On the contrary, this chemical change did not decrease its antibacterial activity against Gram-positive bacterium.

Abstract: As the fossil resource supply situation become more serious and the increasingly serious environment problems, the development of new carbon resource utilization has become an urgent task. Plant cellulose is the most abundant natural resource, which is renewable, nontoxic and degradable, has been paid much attrition by researchers of many countries. This paper reviews recent progress in plant cellulose extract and modification, especially in chemical modification of cellulose derivatives. And the article described cellulose modification technology about pretreatment. The applications of modified cellulose in the field of environmental protection, pharmaceutical, paint and other industries introduced as well. Finally, the current research hotspots of cellulose modification technology were prospected.