W.H. Cheung

Adsorption of acid dyes on chitosan—equilibrium isotherm analyses

Abstract The ability of chitosan, derived from deacetylated crab shell chitin, to remove acid dyes from effluent solution by adsorption has been studied. Equilibrium isotherms for the adsorption of five acid dyes, Acid Green 25 (AG25), Acid Orange 10 (AO10), Acid Orange 12 (AO12), Acid Red 18 (AR18) and Acid Red 73 (AR73), on chitosan were measured experimentally. Results were analysed by the Langmuir, Freundlich and Redlich–Peterson (R–P) equation using a linearised correlation coefficient. The Langmuir isotherm gave the best correlation for the adsorption of AG25, AR18, AR73 and AO12 while the composite Freundlich isotherm gave excellent correlation for AO10. The equilibrium data were then analysed using five different non-linear error analysis methods and two significant findings were obtained. Firstly, the order of isotherm selection was changed showing that the R–P equation had the lowest error values for all five acid dye-chitosan isotherms. Secondly, the values of the individual isotherm constants changed with the error methodology selected.

Equilibrium studies for the sorption of lead from effluents using chitosan

The sorption of lead ions from aqueous solution onto chitosan has been studied. Equilibrium studies have been carried out to determine the capacity of chitosan for lead ions. The effects of solution pH and chitosan particle size on the sorption capacity have been studied.The experimental data were analyzed using three equilibrium isotherm correlations, namely, Langmuir, Freundlich and Redlich-Peterson equations. The linear correlation coefficients were determined for each isotherm and the Freundlich provided the best fit. In addition, error functions have been used to determine the alternative single component equilibrium isotherm parameters by non-linear regression due to the inherent bias in using the correlation coefficient from the linearization. This technique enables the best fit isotherm parameters to be used in the equilibrium equations for the sorption of lead ions on chitosan within the limits and assumptions of the various error analysis methods.

Enhancing the adsorption capacities of acid dyes by chitosan nano particles

In the present study, nanochitosan emulsion has been produced in a suspension form by adding tripolyphosphate solution into a chitosan solution drop-wise. The adsorption capacities of four acid dyes, namely, Acid Orange 10 (AO10), Acid Orange 12 (AO12), Acid Red 18 (AR18) and Acid Red 73 (AR73) on nanochitosan, have been determined to be 1.77, 4.33, 1.37 and 2.13 mmol l(-1), respectively. The nanochitosan dye capacities were compared with normal chitosan capacities which were 1.54, 2.66, 1.11 and 1.25 mmol l(-1) for AO10, AO12, AR18 and AR73, respectively. In all cases, the nanochitosan has a higher capacity. The mechanism of acid dye adsorption and the effect of pH are also discussed.

Municipal Solid Waste Utilization for Integrated Cement Processing with Waste Minimization: A Pilot Scale Proposal

A novel design of an integrated process for cement production incorporating municipal solid waste (MSW) separation and combustion has been developed. The novel design offers significant opportunities for waste minimization. The MSW combustion system design incorporates the use of supplementary fuel from waste marine oil. Very high temperature, 1200C, high turbulence and high residence time, >4 s, are achieved. This results in very high burnout of MSW, resulting in negligible particulate organic matter to form dioxin by de-novo synthesis. The energy produced is used for the cement process calcination of limestone and residual heat is converted into energy to drive the cement plant. The calcination process itself is used as a large scrubber to remove SO x and HCl, the latter minimizing the chance of dioxin formation further. A front end materials recovery and recycling facility, MRRF, is used to remove valuable recyclable components, chlorine-based plastics and metal-containing materials, such as batteries. The combustion of the MSW achieves a 85–90% volume reduction and the MSW ash is used as a feedstock for the production of the cement clinker.

Characteristics of Chemical Modified Activated Carbons from Bamboo Scaffolding

Abstract In this study, bamboo scaffolding was used to produce activated carbon by carbonization at 600 °C and 900 °C with the purge of nitrogen. The 600 °C char was then further modified chemically by acids and alkalis by reflux for 6 hours. The produced chars were then characterized by nitrogen adsorption isotherm, He pyncometry, pH, elemental analysis and Boehm titration. For most of the chemically modified carbons, the micropore surface areas and volumes have increased compared with the 600 °C char, while the mesopore surface areas and volumes slightly decreased, which may have been due to the dissolving of some of the permeated inorganic matter and oxidizing deposited carbon that blocks the pore openings. For the acidic modified carbons, larger amounts of acidic groups were present in the carbons after being activated by phosphoric acid, phosphoric acid further treated with 2 mol·L −1 nitric acid, and calcium hydroxide. Although carbon treated with 2 mol·L −1 and 5 mol·L −1 nitric acid also produced high acidity, the surface areas and pore volumes were relatively low, due to the destruction of pores by nitric acid oxidation. The reduction of porosity may impair the adsorption capacity.

Systematic Analysis of Carbon Dioxide Activation of Waste Tire by Factorial Design

Abstract In this study, waste tire was used as raw material for the production of activated carbons through pyrolysis. Tire char was first produced by carbonization at 550°C under nitrogen. A two factorial design was used to optimize the production of activated carbon from tire char. The effects of several factors controlling the activation process, such as temperature (850–950 °C), time (2–6 h) and percentage of carbon dioxide (70%–100%) were investigated. The production was described mathematically as a function of these three factors. First order modeling equations were developed for surface area, yield and mesopore volume. It was concluded that the yield, BET surface area and mesopore volume of activated carbon were most sensitive to activation temperature and time while percentage of carbon dioxide in the activation gas was a less significant factor.