Kunitaro Kawazoe

STUDY OF THERMAL REGENERATION OF SPENT ACTIVATED CARBONS: THERMOGRAVIMETRIC MEASUREMENT OF VARIOUS SINGLE COMPONENT ORGANICS LOADED ON ACTIVATED CARBONS

Thermogravity analysis of the activated carbons loaded with 32 different single component organics showed that TGA curves could be classified into three distinct groups with regard to their shapes. The organics that belong to Group (I) are rather volatile and TGA curves can be explained by equdibrium desorption model. Group (II) organics are relatively easy to decompose and TGA curves were interpreted in terms of first-order cracking kinetics. The parameters included in these models were obtained from the measured TGA curves by utilizing half desorbed temperature T12 and reciprocal slope of TGA at T12, ΔT. Group (III) consists of phenol, β-naphtol, lignin etc. and gave high residuals on activated carbons after heating up to 800°C. This suggests that these organics are the ones that are critical to the ordinary thermal regeneration method. A rough classification of organics into these groups was done by using the boiling point and the aromatic carbon content.

Adsorption of tri- and tetra-chloroethylene from aqueous solutions on activated carbon fibers

Abstract Recently the contamination of groundwater by trichloroethylene and related compounds have become a new environmental problem. As the first step to clarify the feasibility of applying newly developed adsorbent, activated carbon fiber (ACF), to adsorption treatments of water taken from such a contaminated groundwater source, the adsorption equilibrium and the adsorption rate of trichloroethylene and tetrachloroethylene from aqueous solutions on four ACFs with different pore-size distribution were investigated. The adsorption capacities of ACFs having larger volume of micropores are larger than those of granular activated carbons (GACs) usually used at present. Also, the adsorption rate on ACFs is far more rapid in comparison with GAC adsorption because of smaller diffusion path.

Trihalomethane adsorption on activated carbon fibers

Abstract Adsorption isotherms of three trihalomethanes (THMs) involving CHCl 3 , CHBrCl 2 and CHBr 2 Cl on activated carbon fibers (ACFs) were measured. Adsorption capacities of the ACFs for these THMs were found to be comparable with or slightly larger than those of granular activated carbons (GACs) which have been widely used for trihalomethane control in drinking water. Also, the breakthrough curve prediction was successfully carried out using a mathematical model on the basis of the assumption that the adsorption equilibrium is instantaneously established when a THM solution contacts the ACF. In practice, THM removal from drinking water was investigated at water works using bench-scale ACF adsorption columns. The volume of water treated at a space velocity (SV) of about 100 h −1 was approx. 401 (g-ACF) −1 .

Sorption and accumulation of cadmium in the sediment of the Tama River

Cadmium contents in the water and the sediment samples collected from the Tama River and several branches were measured. Cadmium (above 0.005mgl−1) was detected in only four of the water samples, while the sediment samples showed cadmium content of 1.0–9.8 μg g−1 dry sediment. Cadmium concentration in the sediments of the main stream was correlated against ignition loss of the samples and it was found that 1 g of ignition loss (organic matter) corresponded to 35 μg of cadmium. The batch adsorption experiment in the laboratory using an aqueous solution of cadmium for 14 sediment samples with a higher concentration of cadmium indicated that the amount adsorbed by the sediment is highly dependent on the ignition loss. The amount adsorbed on unit mass of ignition loss qIL could be correlated by a Freundlich-type equilibrium relation as qIL=kILC1n where C is the equilibrium concentration in the aqueous phase ranging between 7 × 10−3 and 10 mg l−1, while kIL and n are equilibrium constants. The adsorption rate measurement showed that the intraparticle diffusion coefficient of cadmium in the sediment was about 1.1 × 10−6 cm2s−1, which is of a reasonable order of magnitude assuming the pore diffusion mechanism inside the particle. The results suggest that suspended solid particles of high organic content in flowing water contribute significantly to the transport of cadmium along the river.

Interpretation for the micropore diffusivities of gases in molecular-sieving carbon

Abstract Physical interpretations were tried for the experimental data on micropore diffusivity of gases in molecular-sieving carbon (MSC) reported by the authors elsewhere. Micropore diffusion is so-called activated diffusion in the space between graphite layer planes and diffusion coefficient is expressed as D = D 0 exp( −E/RT ). The experimentally determined D 0 for Ar, Kr, Xe, N 2 , and CH 4 agreed with D 0 estimated theoretically from the activation energy, E , and structural parameters of MSC by using the absolute rate theory. The isosteric heats of adsorption, q st , and E are compared with those calculated on the basis of Lennard-Jones potential with London expressions for the space between two graphitized carbon surfaces. The values of q st and E for Ar, Kr, and Xe suggested that the distance of the two graphite layers was 4.4 ± 0.1 A.

Water treatment by pitch-based activated carbon fiber

Abstract Recently lakes, swamps and suburban rivers of cities have become growingly polluted according to various kinds of waste water drainage. For domestic and industrial waters much call has been made on advanced water treatment techniques to where more adsorption operation is employed by granular and powdered activated carbon for removal of organic substances, color, odor, etc. We already succeeded in a promising result from two experiments at Kashiwai Water Works of Chiba Prefecture and Murano of Osaka Prefecture using a pitch-based activated carbon fiber (ACF). This paper deals with the further development that the pitch-based ACF has been reformed and the development of higher performance ACF ventured on.

Sorption and Accumulation of Cadmium in the Sediment of the Tama River

Abstract Cadmium contents in the water and the sediment samples collected from the Tama River and several branches were measured. Cd was detected (above 0.005 mg/l) in only four of the water samples, while the sediment samples showed Cd content of 1.0-9.8 μ/g dry sediment. Cadmium concentration in the sediments of the main stream was correlated against ignition loss of the samples and it was found that 1 g of ignition loss (organic matter) corresponded to 35 μg of Cd. Batch adsorption experiment trom aqueous solution of Cd using 14 sediment samples at higher Cd concentration in the laboratory indicated that the amount adsorbed on the sediment is highly dependent on the ignition loss and the amount adsorbed on unit mass of ignition loss, q IL , could be correlated by Freundlich type equilibrium relation as q IL = k IL C l/n where C is the equilibrium concentration in aqueous phase that ranged between 7x 10 -3 and 10 mg/l, while k IL and n are equilibrium constants. The adsorption rate measurement showed that the intra-sediment-particle diffusion coefficient of Cd was about 1.1 x 10 -6 cm 2 /sec, which is of reasonable order of magnitude if the pore diffusion mechanism is assumed inside the particle The results suggest that suspended solid particles of high organic content in flowing water have a significant contribution to the transport of Cd along the river.