Linda B. L. Lim

Enhancing adsorption capacity of toxic malachite green dye through chemically modified breadnut peel: equilibrium, thermodynamics, kinetics and regeneration studies.

Breadnut skin, in both its unmodified (KS) and base-modified (BM-KS) forms, was investigated for its potential use as a low-cost adsorbent for the removal of toxic dye, malachite green (MG). Characterization of the adsorbents was carried out using scanning electron microscope, X-ray fluorescence and Fourier transform infra-red spectroscopy. Batch adsorption experiments, carried out under optimized conditions, for the adsorption of MG were fitted using five isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Sips) and six error functions to determine the best-fit model. The adsorption capacity was greatly enhanced when breadnut skin was chemically modified with NaOH, leading to an adsorption capacity of 353.0 mg g−1, that was far superior to most reported adsorbents for the removal of MG. Thermodynamics studies indicated that the adsorption of MG was spontaneous on KS and BM-KS, and the reactions were endothermic and exothermic, respectively. Kinetics studies showed that both followed the pseudo-second order. Regeneration experiments on BM-KS indicated that its adsorption capacity was still maintained at>90% even after five cycles. It can be concluded that NaOH-modified breadfruit skin has great potential to be utilized in real-life application as a low-cost adsorbent for the removal of MG in wastewater treatment.

Sorption characteristics of peat of Brunei Darussalam V: removal of Congo red dye from aqueous solution by peat

AbstractPeat collected from Panaga, Brunei Darussalam, shows strong affinity towards the adsorption of Congo red (CR) dye from aqueous solution. The adsorption capacity of Bruneian peat under optimized conditions of shaking time, settling time, and medium pH is determined to be 10.1 mg g−1 at equilibrium. Adsorption of CR on Bruneian peat follows monolayer adsorption with small contribution to multilayer formation qualifying the validity of the Redlich–Peterson model, which is further supported by error function determination. In addition, changes in peat structure and surface were studied using scanning electron microscopic and X-ray fluorescence techniques. Kinetics studies were in agreement with the pseudo-second-order model and the adsorption reaction proceeds according to intra-particle diffusion.

Sorption characteristics of peat from Brunei Darussalam for the removal of rhodamine B dye from aqueous solution: adsorption isotherms, thermodynamics, kinetics and regeneration studies

AbstractThis work reports the application of peat as cheap and effective adsorbent for the removal of rhodamine B dye (RhB) from aqueous solution. The effects of contact time, settling time and pH were studied to obtain the optimum conditions for adsorption studies. Optimum contact time was 4 h with 1 h settling time and ambient pH was used throughout the study. Adsorption isotherms, namely Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Redlich–Peterson and Sips, were employed in this study together with error functions to predict the most suitable isotherm model for the adsorption process. The Sips isotherm was found to be the best fit model. The maximum adsorption capacities (qmax) obtained for the adsorption at 298, 313, 324, 334 and 344 K are 162.87, 166.22, 172.45, 186.82 and 201.19 mg g−1, respectively. Thermodynamic parameters indicate that the adsorption was spontaneous, feasible and endothermic in nature. Pseudo second order kinetic model fitted well to the adsorption of RhB on peat. Regener...

Removal of Methyl Violet 2B from Aqueous Solution Using Casuarina equisetifolia Needle

One of the major contaminants of water bodies is dye pollutants that come from textile, paper, and leather industries. In this study, Casuarina equisetifolia needle (CEN) is used to remove methyl violet 2B (MV) from aqueous solutions. Batch experiments were done to investigate the contact time, effect of pH, initial dye concentrations, and temperature. Langmuir and Freundlich isotherm models were used to describe the interaction between the adsorbate and adsorbent. The sorption mechanism was described using Lagergren 1st order, pseudo 2nd order, and Weber-Morris intraparticle diffusion models. FTIR spectroscopy was used to analyze the functional groups of CEN before and after sorption with MV. Optimal conditions were found to be at room temperature with 2 h contact time and no pH adjustment was needed. Experimental data was best fitted onto Langmuir model with maximum adsorption capacity of 164.99 mg/g, while pseudo 2nd order best described the experimental data for the kinetics study. Thermodynamic parameters such as change in Gibbs free energy (), enthalpy (), and entropy () were also investigated.

Effective adsorption of toxic brilliant green from aqueous solution using peat of Brunei Darussalam: isotherms, thermodynamics, kinetics and regeneration studies

Peat, a natural adsorbent, has been successfully used for the removal of the hazardous water-soluble cationic dye, brilliant green (BG). Characterization of peat was carried out by determining its physical and chemical compositions such as moisture, ash, carbon%, hydrogen%, nitrogen%, and sulphur% (CHNS), crude protein and crude fat. X-ray fluorescence (XRF) was used for the determination of the percentage of elements present in peat. Functional groups present in peat were analyzed using Fourier transform infra-red (FTIR). Changes in the surface morphology of peat before and after treatment with BG were studied using Scanning Electron Microscopy (SEM). The optimization time required for establishment of an adsorption equilibrium is determined to be 2.0 h. The ambient pH of BG was used throughout the study. Adsorption isotherm models such as Langmuir, Freundlich, Halsey, Temkin, Redlich–Peterson (R–P) and Sips were simulated to fit with the experimental equilibrium data. Based on linear regression, simulated isotherm models and error analyses, the R–P isotherm fitted well for the adsorption of BG by peat. Adsorption kinetics was found to follow the pseudo second order model, with a rate constant of 0.39 g mmol−1 min−1. BG-loaded peat was successfully regenerated using 0.01 M sodium hydroxide (NaOH) solution for up to 5 consecutive cycles, while maintaining high adsorption ability of 98% even after the 5th cycle.

The removal of rhodamine B dye from aqueous solution using Casuarina equisetifolia needles as adsorbent

Abstract Casuarina equisetifolia needle (CEN), a lignocellulosic-rich and sustainable material, was used in order to investigate its ability as an adsorbent to remove rhodamine B (RB) dye from aqueous solution. Fourier Transform Infrared spectrometer was used to characterise CEN functional groups and scanning electron microscope was used to study its surface morphology. Batch experiments were done in order to determine the effect of some parameters such as adsorbent dosage, initial pH, contact time, ionic strength, temperature and initial dye concentration. Kinetics, isotherm modelling and thermodynamics studies were also performed in order to explore an insight into the mechanism of the adsorption process. The study showed that the adsorption of RB by CEN is endothermic in nature and follows the pseudo-second-order kinetics model. The Langmuir isotherm model fitted the experimental data best with a maximum adsorption capacity of 82.34 mg g−1.

Diastereoselective free-radical reactions. Part 2. Synthesis of 2-deoxy-β-C-pyranosides by diastereoselective hydrogen-atom transfer

C-Glycosides of 2,3-dideoxy-arabino-heptulosonate esters are prepared from the corresponding 2,3dideoxy-1-phenylsulphonyl derivatives by reductive desulphonylation with lithium naphthalenide and quenching of the so-formed enolate with appropriate alkyl halides. These C-glycosides are saponified and decarboxylated by the Barton O-acyl thiohydroxamate protocol to give 2-deoxy-β-C-glycosides with very high diastereoselectivities.

Diastereoselective free-radical reactions. Part 3. The methyl glucopyranos-1-yl and the 1,2-O-isopropylideneglucopyranos-1-yl radicals: conformational effects on diastereoselectivity

The 3,4,6-tri-O-benzyl-2-O-t-butyldimethylsilyi-1-O-methyl-D-glucopyranos-1-yl and the 3,4,6-tri-O-benzyl-1,2-O-isopropylidene-D-glucopyranos-1-yl radicals are quenched with high selectivity (> 25 : 1) from the α- and β-face, respectively, by t-dodecanethiol. The reasons for this selectivity are discussed and the preparation of the radical precursors is presented. An improved preparation of 3,4,6-tri-O-benzyl-D-glucopyranose is described.

Composition of the essential oil of Plumeria obtusa L.

The essential oil of fresh flowers of Plumeria obtusa L. collected in Brunei Darussalam was isolated by hydrodistillation and examined by GC–MS. Forty-seven components were identified, representing 97% of the oil, with benzyl salicylate (39%), benzyl benzoate (11%), (2E, 6E)-farnesol (8%) and (E)-nerolidol (5%) as major constituents. The remaining identified constituents of the oil (34%) were found as minor constituents (≤3%). Copyright

Remediation of Rhodamine B Dye from Aqueous Solution Using Casuarina equisetifolia Cone Powder as a Low-Cost Adsorbent

The removal of toxic dye rhodamine B (RB) from aqueous solution was achieved by using Casuarina equisetifolia cone (CEC) as an adsorbent. Batch experiment method was used in order to investigate the effects of contact time, pH, temperature, ionic strength, and dye concentration on the adsorption process. Kinetics and isotherm theoretical models were applied on the experimental data and it was found that the pseudo-2nd-order kinetics and the Langmuir isotherm model best fitted into the data. The Langmuir maximum adsorption capacity for CEC was determined as 49.5 mg g−1. The adsorption of RB onto CEC is thermodynamically favourable, feasible, and endothermic in nature.