Chinkap Chung

Exchange of self-assembled thiol monolayers on gold: characterization by FT-IR external reflection spectroscopy☆

Abstract The exchange behavior of various thiol monolayers self-assembled on a gold surface is described. FT-IR external reflection spectroscopy was used for monitoring of the self-exchange of unsubstituted alkanethiol with the aid of deuterated thiol. Intensity changes of the absorption peaks for a specific functionality were used for the quantization of thiols in the monolayers. Exchange of compact monolayers such as eicosanethiol with the same type of alkanethiol in ethanol solution was found to be very slow. We used n-eicosanethiol [CH3(CH2)19SH] and partially deuterated eicosanethiol [CD3(CH2)19SH] in order to avoid the chain length difference effect of adsorption and maintain exactly the same chain length of molecules. The exchange of the non-compact ferrocene terminated alkanethiol monolayer with dodecanethiol was faster than the self-exchange of the compact unsubstituted alkanethiol monolayer. The result shows that the compactness of the monolayer is critical to the exchange kinetics of self-assembled monolayers.

Implementation of batchwise bioscouring of cotton knits

The examination of critical factors determining the performance of bioscouring showed that a short treatment of the fabric at greater than 80°C after pectinase treatment at 60°C was essential for removal of waxes from the fabric as demonstrated by diminished intensities of methylene peaks in FT-IR measurements. Batch-wise bioscouring of cotton knits was carried out several times with post-treatment at 80°C using a rapid dyeing machine. The dye-ability of bioscoured knits was as good as the companys alkaline scoured ones with slightly higher K/S values. Water pollution caused by effluents of bioscouring and alkaline processes were estimated, as well as that due to the input of chemicals and enzymes. Higher BOD:CODCr ratios for enzymes indicated their biodegradable character. After calculation of energy consumption using a simulation program, an economic evaluation of the two processes was done on the basis of one ton production by considering the costs of chemicals and enzyme, water usage, energy consumption and waste water treatment charge.

Rapid estimation of biochemical oxygen demand using a microbial multi-staged bioreactor

Abstract A multi-staged bioreactor system consisting of Trichosporon cutaneum immobilized in Ca-alginate bead and nylon columns was prepared for the estimation of biochemical oxygen demand (BOD) of waste waters. When a sample solution containing the equivalent amount of glucose and glutamic acid (GGA) was injected into the reactor system, the dissolved oxygen (DO) in the sample was decreased with the concentration of GGA. The response time was within 10 min. A linear relationship was observed between the DO decrease and a concentration below 90 ppm glucose and 90 ppm glutamic acid (5-day BOD, 130 ppm). This reactor system was applied to untreated waste waters. Good comparative results were obtained between BOD estimated by this reactor system and that determined by the conventional 5-day method.

On-line monitoring of cellulase treatment by differential refractometer

Cellulase treatment of cellulose fibers needs to be monitored to give proper weight loss without significant strength loss. On-line monitoring of cellulase treatment is presented which can monitor the weight loss of cotton fabrics by measuring differential refractive index in real time. On-line monitoring was tried under the condition where the cellulase treatment of scoured 100% cotton knits would give weight loss of about 6.6% during one hour cellulase treatment. For comanalyses processing solutions with treatment time of 5, 10, 20, 30, 45 and 60 minutes were taken out, and subjected to sugar analyses using total organic carbon (TOC), and dinitrosalicylic acid (DNS) method as well as HPLC analyses. HPLC analyses showed that cellobiose and glucose were the major components resulting from cellulase treatment of cotton fabric. TOC and differential refractive index measurement proved to be linear to total sugar concentration while DNS method result was dependent on the type of sugar. Various sugar concentrations of the processing solutions measured by these methods were compared with HPLC measurements and correlated with the actual weight loss of the cotton fabric processed. The on-line monitoring device using differential refractometer gave a real time signal which was independent of the ratio of cellobiose and glucose but dependent on the total sugar concentration. The device was also non-destructive.

Characterization of cotton fabric scouring by Fourier transform-infrared attenuated total reflectance spectroscopy, gas chromatography-mass spectrometry and water absorption measurements

Surface sensitive Fourier transform-infrared attenuated total reflectance (ATR) accessories using different crystals as well as incident beam angles were examined for the characterization of cotton fabric scouring. The extra sharp antisymmetric and symmetric C-H stretching peaks due to long chain alkyls at 2918 and 2849 cm−1 were observed in greige cotton fabrics with a tendency to be more profound with the ATR cell with bigger incident angles and a higher refractive index, due to less depth of penetration. Water absorption data and gas chromatography-mass spectrometry analyses indicated that these peaks were mostly caused by secondary added paraffin wax of higher linear alkanes (C22 to C30) and cotton wax of C16 and C18 fatty acids in free form. Absence of these peaks alone did not result in sufficient water absorption. No observation of carboxylate (COO−) peak at 1600 cm−1 together ensured a successful scouring. Presence of this weak peak can be further confirmed by the reversible shift between 1600 cm−1 and 1750 cm−1 of protonated carboxylic acids (COOH) under non-destructive and quick HCl or NH3 vapor exposures on cotton samples.