Ru-Ling Tseng

KINETIC MODELING OF LIQUID-PHASE ADSORPTION OF REACTIVE DYES AND METAL IONS ON CHITOSAN

The rates of adsorption of three commercial reactive dyes and Cu(II) from water in the absence and presence of complexing agents using chitosan were measured at 30 degrees C. Three simplified kinetic models, i.e., pseudo-first-order, pseudo-second-order, and intraparticle diffusion, were tested to investigate the adsorption mechanisms. It was shown that the adsorption of reactive dyes and Cu(II) in the absence of complexing agents could be best described by the intraparticle diffusion model, whereas that of Cu(II) in the absence of complexing agents such as EDTA, citric acid, and tartaric acid by the pseudo-second-order equation. Kinetic parameters of the three models and the normalized standard deviations between the measured and predicted results were also calculated and discussed.

Comparative adsorption of metal and dye on flake- and bead-types of chitosans prepared from fishery wastes

The adsorption capacities and rates of Cu(II) and a commercial reactive dye RR222 on flake- and bead-types of chitosans prepared from three fishery wastes (shrimp, crab, and lobster shells) were compared at 30 degrees C. It was shown that all equilibrium isotherms could be well fitted by the Langmuir equation. The adsorption capacity of Cu(II) on flake- and bead-types of chitosans appeared to be comparable, but the adsorption capacity of RR222 on bead type was much larger than that on flake type by a factor of 2. 0-3.8. The rates of dye adsorption on both types of chitosans indicated different controlling mechanisms. In addition, the bead type of chitosans exhibited a greater rate compared to the flake type.

Adsorption behavior of reactive dyes from aqueous solutions on chitosan

The capability of the use of chitosan for removing vinyl sulfone and chlorotriazine reactive dyes from aqueous solutions was examined, including equilibrium and dynamic studies. Experiments were performed as a function of dye concentration, and the amount and particle size of chitosan. It was shown that the adsorption capacities of chitosan were comparatively high for the three investigated dyes. The equilibrium data could be best fitted by the Redlich–Peterson equation over the entire concentration range (50–500 g m−3). A comparison of the adsorption capacity among such adsorbents as chitin and powdered activated carbon was made. Two rate parameters were finally obtained to describe the adsorption process on a quantitative basis. These parameters could be well correlated to the amount and particle size of dry chitosan. ©1997 SCI

Enhanced abilities of highly swollen chitosan beads for color removal and tyrosinase immobilization.

The enhancement of abilities for the removal of reactive dyes and immobilization of tyrosinase onto highly swollen chitosan beads was demonstrated compared to the use of common chitosan flakes. Chitosan was prepared from natural cuttlebone wastes. It was shown that the adsorption capacity of dyes at 30 degrees C using swollen chitosan beads was around five times greater than that using common chitosan flakes. The adsorption of dyes using swollen beads was faster by 10-40% depending on the types of dyes. Finally, the capacity of tyrosinase immobilization onto swollen beads was about 14 times greater than chitosan flakes, which was reflected by the higher yield of 3,4-dihydroxyphenylalanine from tyrosine and ascorbic acid in the heterogeneous catalytic system.

The Ability of Activated Clay for the Adsorption of Dyes from Aqueous Solutions

A low-cost inorganic acid-activated clay was used as adsorbent for the adsorption of six dyes (two basic, one acidic, one disperse, one direct dye, and one reactive) from aqueous solutions. The adsorption capacity was comparatively high for basic dyes and was lower for disperse, direct, and reactive dyes. The equilibrium data could be well described by the Langmuir equation over the entire range of concentration (50∼500 mg dm−3). In addition, the effect of temperature on the adsorption was examined and the thermodynamic data were determined. Based on the adsorption capacity only, it was generally shown that activated clay was more effective compared to other commonly used adsorbents.

Adsorption of Dyes and Phenols from Water on the Activated Carbons Prepared from Corncob Wastes

Pore structures and physical properties of the activated carbons prepared from corncob wastes at various activation temperatures (830, 860, 890°C.) were first studied. Equilibria and rates of adsorption of two commercial dyes, phenol, and 3-chlorophenol from water on such activated carbons were then measured at 30 °C. All adsorption isotherms of the solutes could be well fitted by the Langmuir equation. Three simplified kinetic models including pseudo-first-order equation, pseudo-second-order equation, and intraparticle diffusion model were selected to follow the adsorption processes. It was shown that the adsorption of both phenols could be best described by the pseudo second-order equation, but that of both dyes best by the intraparticle diffusion model. Kinetic parameters of each best-fit model were calculated and discussed.

Solute adsorption and enzyme immobilization on chitosan beads prepared from shrimp shell wastes

The equilibrium and kinetics of adsorption of reactive dye RR222 and Cu2+, and the activity of immobilization of acid phosphatase, on highly swollen chitosan beads were examined at 30 degrees C. The chitosan was prepared from shrimp shell wastes and was cross-linked with different dosages of glutaraldehyde or glyoxal (100-80,000 mg/l). It was shown that the amounts of solute adsorption and the immobilization capacity of acid phosphatase on cross-linked chitosan beads were substantially affected by their degree of cross-linking. The cross-linking rate of chitosan with glutaraldehyde could be described by a pseudo-second-order equation and the cross-linking equilibrium by the Freundlich equation. This provided an experimental method to control the degree of cross-linking of chitosan beads. Finally, the activity and lifetime of the immobilized enzyme were measured to evaluate the application potential.

Pore structure and adsorption performance of the activated carbons prepared from plum kernels.

According to iodine number, amount of methylene blue adsorption, the BET specific surface area, and the yield, the conditions for preparing activated carbons as adsorbents from plum kernels were optimized. The activation temperature and time tested were in the ranges 750-900 degrees C and 1-4 h, respectively. Adsorption isotherms of two commercial dyes and phenol from water on such activated carbons were measured at 30 degrees C. It was shown that the optimal activation temperature and time depended on the molar mass of the solutes, and all equilibrium isotherms could be fitted by the Langmuir equation. The experimental results indicated that the prepared activated carbons were economically promising for adsorption removal of dyes and phenol, in contrast to other commercial adsorbents.

Role of Microporosity of Activated Carbons on Their Adsorption Abilities for Phenols and Dyes

The amounts of adsorption of two commercial dyes, phenol, and 4-chlorophenol from water on activated carbons were measured at 30°C. The carbons were prepared from cane (bagasse) piths and were activated by steam. The activation temperature and time were in the ranges of 750–840°C and 2 h, respectively. It was shown that the isotherm data of all four solutes could be well fitted by the Langmuir equation under the conditions studied. The adsorption capacities of the solutes were correlated with the microporosity properties of the activated carbons including micropore volume and external surface area. Finally, the adsorption characteristics of the present carbons was compared with those prepared from various agricultural wastes.

USE OF CHITIN AND CHITOSAN IN LOBSTER SHELL WASTES FOR COLOR REMOVAL FROM AQUEOUS SOLUTIONS

Abstract Chitin and chitosan prepared from lobster shell wastes were used as adsorbents for the removal of various dyes from aqueous solutions. It was shown that high adsorption capacities were observed for reactive dyes. The adsorption equilibrium data could be well described by Langmuir equation under the concentration range investigated (50–500 mg/L). On the basis of Langmuir adsorption capacity, chitosan obtained in this work was found to be more effective compared to chitin and a commercial chitosan.