Ruey-Shin Juang

Use of cellulose-based wastes for adsorption of dyes from aqueous solutions

Low-cost banana and orange peels were prepared as adsorbents for the adsorption of dyes from aqueous solutions. Dye concentration and pH were varied. The adsorption capacities for both peels decreased in the order methyl orange (MO) > methylene blue (MB) > Rhodamine B (RB) > Congo red (CR) > methyl violet (MV) > amido black 10B (AB). The isotherm data could be well described by the Freundlich and Langmuir equations in the concentration range of 10-120 mg/l. An alkaline pH was favorable for the adsorption of dyes. Based on the adsorption capacity, it was shown that banana peel was more effective than orange peel. Kinetic parameters of adsorption such as the Langergren rate constant and the intraparticle diffusion rate constant were determined. For the present adsorption process intraparticle diffusion of dyes within the particle was identified to be rate limiting. Both peel wastes were shown to be promising materials for adsorption removal of dyes from aqueous solutions.

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.

Adsorption of phenol and its derivatives from water using synthetic resins and low-cost natural adsorbents: a review.

In this article, the technical feasibility of the use of activated carbon, synthetic resins, and various low-cost natural adsorbents for the removal of phenol and its derivatives from contaminated water has been reviewed. Instead of using commercial activated carbon and synthetic resins, researchers have worked on inexpensive materials such as coal fly ash, sludge, biomass, zeolites, and other adsorbents, which have high adsorption capacity and are locally available. The comparison of their removal performance with that of activated carbon and synthetic resins is presented in this study. From our survey of about 100 papers, low-cost adsorbents have demonstrated outstanding removal capabilities for phenol and its derivatives compared to activated carbons. Adsorbents that stand out for high adsorption capacities are coal-reject, residual coal treated with H3PO4, dried activated sludge, red mud, and cetyltrimethylammonium bromide-modified montmorillonite. Of these synthetic resins, HiSiv 1000 and IRA-420 display high adsorption capacity of phenol and XAD-4 has good adsorption capability for 2-nitrophenol. These polymeric adsorbents are suitable for industrial effluents containing phenol and its derivatives as mentioned previously. It should be noted that the adsorption capacities of the adsorbents presented here vary significantly depending on the characteristics of the individual adsorbent, the extent of chemical modifications, and the concentrations of solutes.

Heavy metal removal from water by sorption using surfactant-modified montmorillonite

Removal of Cu2+ and Zn2+ from aqueous solutions by sorption on the montmorillonite modified with sodium dodecylsulfate (SDS) was investigated. Experiments were carried out as a function of solution pH, solute concentration, and temperature (25-55 degrees C). The Dubinin-Kaganer-Radushkevick model was adopted to describe the single-solute sorption isotherms. Also, the binary-solute sorption equilibria could be reasonably predicted by the competitive Langmuir model, in which the Langmuir parameters were directly taken from those obtained in single-solute systems. The thermodynamic parameters (DeltaH(o) and DeltaS(o)) for Cu2+ and Zn2+ sorption on the modified clay were also determined from the temperature dependence. The kinetics of metal ions sorption was examined and the pseudo-first-order rate constant was finally evaluated.

Metal removal from aqueous solutions using chitosan-enhanced membrane filtration

The removal of divalent metal ions including Cu(II), Co(II), Ni(II), and Zn(II) from aqueous solutions by membrane filtration was studied with the help of water-soluble chitosan. The Amicon regenerated cellulose YM10 and YM30 were used as ultrafilters. Experiments were performed as a function of aqueous pH, the concentration ratio of chitosan to metals (), and applied pressure (1P). It was shown that at neutral condition the removal of Cu(II) was more efficient compared to other metals. Furthermore, metal removal from acidic solutions (pH < 6) could be enhanced by 6‐10 times via the addition of chitosan. The effect of the presence of inorganic salts on the removal was also studied. Finally, the fouling phenomena during filtration was analyzed by conventional filtration theory considering compressible nature of the deposited gel. ©2000 Elsevier Science B.V. All rights reserved.

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.

A simplified equilibrium model for sorption of heavy metal ions from aqueous solutions on chitosan

The amounts of sorption of Cu2 , Ni2+, and Zn2+ from water on cross-linked chitosan were measured. Experiments were performed as a function of initial pH (2-5), total metal concentration (0.77-17 mol/m3), and metal concentration ratio (0.25-4) at 25 degrees C in single- and binary-metal systems. The sorption was so highly pH dependent that the isotherm could not be described by one specific equation. A simplified equilibrium model was thus proposed considering competitive sorption of proton and metal ions. The number of active sites on chitosan bound with one metal ion was adjustable and model parameters could be graphically determined. Given initial metal concentrations and solution pH, the proposed model could predict the amounts of sorption of proton and metals as well as the equilibrium pH. In general, application of the model parameters calculated in single-metal systems to the prediction of sorption in binary-metal systems was not satisfactory due to a remarkable effect of competitive sorption.

Mass transfer effect and intermediate detection for phenol degradation in immobilized Pseudomonas putida systems

Abstract Phenol degradation by Pseudomonas putida CCRC14365 and cell growth kinetics were compared between the free and Ca-alginate gel-immobilized systems. Trends of the effects of pH and temperature on phenol degradation were similar for both free and immobilized cells. Due to the substrate inhibition effect, free cells could degrade phenol only up to about 600 mg/l. While immobilized cells could tolerate a higher level up to 1000 mg/l, although the degradation rate was slower. Growth kinetics of free cells for degradation of phenol in the concentration range 25–600 mg/l was described by the Haldane model. The diffusion effect was not significant in the immobilized systems from the values of effectiveness factor and Thiele modulus, inferring that the degradation process was governed by intraparticle diffusion and chemical reaction. Unlike the case of free cells, intermediate catechol was detected using immobilized cells at a phenol level of 100–400 mg/l. This implied that the occurrence of medium diffusion resistance in the immobilized systems, which retarded the degradation reaction, might be useful for detection of the intermediates.