John F. Porter

EQUILIBRIUM ISOTHERM STUDIES FOR THE SORPTION OF DIVALENT METAL IONS ONTO PEAT: COPPER, NICKEL AND LEAD SINGLE COMPONENT SYSTEMS

The sorption of three divalent metal ions — copper, nickel and lead — from aqueous solution onto peat in single component systems has been studied and the equilibrium isotherms determined. The experimental data have been analysed using the Langmuir, Freundlich, Redlich-Peterson, Toth, Temkin, Dubinin-Radushkevich and Sips isotherm models. In order to determine the best fit isotherm for each system, six error analysis methods were used to evaluate the data: the coefficient of determination, the sum of the errors squared, a hybrid error function, Marquardts percent standard deviation, the average relative error and the sum of absolute errors. The error values demonstrated that the Sips equation provided the best model for the three sets of experimental data overall.

Sorption Kinetic Analysis for the Removal of Cadmium Ions from Effluents Using Bone Char

The adsorption of cadmium ions onto bone char has been studied using a batch adsorber. The experimental data was analyzed using four sorption kinetic models--the pseudo-first order, the Ritchie second order, the modified second order and the Elovich equations--to determine the best-fit equation for the sorption of metal ions onto bone char. The best-fit equation was identified using the sum of the errors squared (SSE). Finally, equilibrium studies were used to evaluate the sorption capacity of bone char for cadmium ions and experimental results showed this to be 0.57 mmol g-1 at an equilibrium solution concentration of 3.0 mmol dm-3. Since the sorption capacity is relatively high, bone char can be considered as a suitable sorbent for the adsorption of cadmium in wastewater treatment systems.

The removal of dye colours from aqueous solutions by adsorption on low-cost materials

The ability of five low cost adsorbents – rice husk, cotton, bark, hair and coal – to adsorb two basic dyes, namely, Safranine and Methylene Blue, has been studied. Equilibrium isotherms have been determined and analysed using the Langmuir equations. The monolayer saturation capacities for Safranine are 1119, 838, 875, 190 and 120 mg g-1adsorbent and for Methylene Blue are 914, 312, 277, 158 and 250 mg g-1adsorbent for bark, rice husk, cotton waste, hair and coal respectively. A limited number of fixed bed column studies have been performed and the bed depth service time for each dye-adsorbent system has been determined.

Sorption kinetics for the removal of copper and zinc from effluents using bone char

Abstract The removal of copper and zinc ions from aqueous effluents by bone char has been studied in single component sorption systems. The sorption capacity of bone char for copper and zinc is 0.75 and 0.53 mmol per g bone char, respectively. The values indicate that bone char is a suitable sorbent for the two metal ions. The equilibrium isotherms are best described by a Langmuir–Freundlich (L–F) type isotherm equation. The kinetics of sorption of the two metal ions have been analyzed by two kinetic models, namely, the Lagergren pseudo first-order model and the Elovich kinetic model. Kinetic analysis of the two models has been carried out for system variables — initial metal ion concentration and mass of bone char. The rate constants for the two models have been determined and the correlation coefficients have been calculated in order to assess which model provides the best fit predicted data with experimental results. The Elovich equation provides the best fit to experimental data.

Optimised correlations for the fixed-bed adsorption of metal ions on bone char

The sorption of two divalent metal ions, namely, copper and cadmium ions, has been studied due to their toxicity in nature and extensive use in industry. Fixed-bed column experiments with different feed concentrations, flowrates and adsorbent particle sizes have been carried out, evaluating sorption of these two metal ions on bone char. Pilot-plant experimental studies have been performed and two simplified design models, namely, the BDST model and EBRT analysis, have been used to analyse the data. New correlations, incorporating a time-dependent term, have been developed to compensate for the time required for the bed to achieve equilibrium sorption capacity. Finally, predictions of the operating lines on the EBRT plot have been correlated using the two metal ion sorption systems.

The prediction of sorption from a binary mixture of acidic dyes using single- and mixed-isotherm variants of the ideal adsorbed solute theory

Abstract Equilibrium isotherms have been determined for the adsorption of two single-component and one binary acid dye solutions on carbon. The ideal adsorbed solute theory (IAST) has been used to predict isotherm data for the binary system using the single-component dye sorption data alone. A detailed analysis has been carried out to investigate the effect of different error criteria for determining single-component isotherm parameters and their influence on the results of IAS model simulations using the Langmuir and Freundlich isotherm equations. It was found that the “best-fit” single-component isotherm based on the minimum error criteria did not result in the “best-fit” IAS model predictions. Furthermore, the IAS model producing the closest fit to the binary experimental data did not use the same isotherm model as the single-component data for one dye. Reasons for this apparently anomalous behaviour have been discussed and the most likely cause appears to be dye–dye interactions in the binary system.

The effect of calcination on the microstructural characteristics and photoreactivity of Degussa P-25 TiO2

Changes in the microstructural characteristics of Degussa P-25 titania as a result of calcination have been studied using XRD, BET and TEM. The photocatalytic activities of the samples were also examined using the degradation of phenol as a model reaction. The results indicate firstly that calcination significantly affects both microstructural characteristics and photoactivity and secondly that there is an apparent relationship between photocatalytic activity and certain microstructural characteristics. Over the range of calcination temperatures and durations studied, the sample calcined at 923 K for 3 hours revealed the highest photoreactivity, which can be ascribed to an improvement in crystallinity on calcination. The increase in the rutile content and grain growth caused by the calcination at higher temperatures were observed to decrease the photocatalytic activities of the TiO2 samples.

Equilibrium Parameters for the Sorption of Copper, Cadmium and Zinc Ions onto Peat

This paper details a study into the sorption of three divalent metal ions—namely cadmium, copper and zinc—onto peat, in single component, binary and ternary systems. The Langmuir Freundlich and Redlich–Peterson equilibrium isotherms for each metal ion in each system have been determined and correlated. The Langmuir isotherms have been found to have the highest regression correlation coefficients.

Elovich equation and modified second-order equation for sorption of cadmium ions onto bone char

The removal of cadmium ions from water by sorption onto bone char has been studied. Bone char, traditionally used for colour removal in sugar refining, is produced by the carbonisation of animal bone. Batch experiments were carried out to study the effects of initial cadmium ion concentration and bone char mass on the sorption rate. The experimental contact data were analysed using the Elovich model, previously used to describe the kinetics of gas adsorption on solids, and the Ritchie model, a modified second-order kinetics equation. Initial analysis of the data, using the Ritchie model, was poor and therefore a modification was incorporated to make the Ritchie model predictions correlate the experimental data more accurately. Both the Elovich and modified Ritchie equations accurately predict the sorption capacity of cadmium on bone char, however, the sorption kinetics, derived from the differential forms of the two equations, were correlated better using the Elovich equation. © 2000 Society of Chemical Industry

Solar photocatalytic thin film cascade reactor for treatment of benzoic acid containing wastewater.

A solar photocatalytic cascade reactor was constructed to study the photocatalytic oxidation of benzoic acid in water under various experimental and weather conditions at HKUST. Nine stainless steel plates coated with TiO(2) catalyst were arranged in a cascade configuration in the reactor. Photolytic degradation and adsorption were confirmed to be insignificant total organic carbon (TOC) removal mechanisms. A turbulent flow pattern and, hence, improved mixing in the liquid film were achieved due to the unique cascade design of the reactor. The photoinduced consumption of oxygen during reactions was demonstrated in a sample experiment. The proposed rate equations provided good fits to 90 data points from 17 experiments. The regression results showed that the TOC removal rates averaged over 30 min intervals did not illustrate significant dependence on TOC(0) and that I(mean) was more important in affecting the photocatalytic process within the ranges of the data examined. The percentage removal of TOC in 7 l of 100 mg/l (or 100 ppm) benzoic acid solutions increased from 30% to 83% by adding 10 ml of hydrogen peroxide solution (30 wt%). Hydrogen peroxide was also shown to enhance the efficiency of the degradation process at elevated temperatures. Ortho-, meta- and para-hydroxybenzoic acids were identified by HPLC analysis as the intermediates of benzoic acid during reactions without the addition of hydrogen peroxide solutions.