Thomas F. O'Dwyer

Advances in poultry litter disposal technology--a review.

The land disposal of waste from the poultry industry and subsequent environmental implications has stimulated interest into cleaner and more useful disposal options. The review presented here details advances in the three main alternative disposal routes for poultry litter, specifically in the last decade. Results of experimental investigations into the optimisation of composting, anaerobic digestion and direct combustion are summarised. These technologies open up increased opportunities to market the energy and nutrients in poultry litter to agricultural and non-agricultural uses. Common problems experienced by the current technologies are the existence and fate of nitrogen as ammonia, pH and temperature levels, moisture content and the economics of alternative disposal methods. Further advancement of these technologies is currently receiving increased interest, both academically and commercially. However, significant financial incentives are required to attract the agricultural industry.

Removal of Lead(II) Ions from Aqueous Solutions Using a Modified Cellulose Adsorbent

A series of adsorption studies were carried out on a glycidyl methacrylate-modified cellulose material functionalised with imidazole (cellulose–g-GMA-imidazole) to assess its capacity towards the removal of Pb(II) ions from aqueous solution. The study sought to establish the effect of a number of parameters on the removal of Pb(II) ions from solution by the cellulose–g-GMA-imidazole. The effect of initial metal concentration, contact time and solution temperature on the removal of Pb(II) ions from solution by the cellulose–g-GMA-imidazole was assessed. Cellulose–g-GMA-imidazole sorbent showed an uptake of ca. 72 mg/g of Pb(II) ions from aqueous solution at 23°C. The adsorption process is best described by the Langmuir adsorption model and the thermodynamics of the process suggest that the binding process is exothermic. The kinetics of the adsorption process indicated that the uptake of Pb(II) ions occurred within 40 min and that pseudo-second-order kinetics best describe the overall adsorption process.

An investigation of surfactant and enzyme formulations for the alleviation of insect contamination on Hybrid Laminar Flow Control (HLFC) surfaces

Abstract Hybrid Laminar Flow Control (HLFC) is an active drag reduction technique that requires a small amount of air to be sucked through a porous skin surface, thus stabilising the boundary layer and permitting extended laminar flow along the wing surface. Contamination of the laminar flow surfaces by insects is a major concern for this technology. An overview of insect contamination and mitigating solutions is provided as background to research undertaken. The paper reports on an experimental investigation into the potential use of surfactants and enzymes as additives to contamination alleviation fluids. It was demonstrated that both approaches have merit. It is concluded that the use of fluorosurfactant containing solutions is preferable to enzyme borne solutions, partly due to the need to control the temperature of the enzyme solution.

Adsorption of Aniline from Aqueous Solution Using Copper-exchanged ZSM-5 and Unmodified H-ZSM-5

Three medium-pore aluminosilicates were investigated with a view to examining their potential as adsorbents for the removal of aniline from aqueous solutions. H-ZSM-5 was exchanged with copper to prepare two different metal-loaded zeolites. The aqueous stability of the copper-exchanged zeolites was then examined by assessing the quantity of copper leached from each zeolite into solution as a function of pH. The optimum stability range with minimal copper leaching occurred between pH values of 5 and 9. The adsorption of aniline from aqueous solution onto each of the three zeolites was carried out within this pH window and the influence of the exchanged copper on the uptake level was assessed. The sorption experiments indicated an uptake level of approximately 40 mg/g for each zeolite. In all cases, the process followed the Langmuir adsorption model with the level of aniline adsorbed being largely unaffected by a change in temperature or the presence of extra-framework copper.

An investigation into the adsorption of aniline from aqueous solution using H-beta zeolites and copper-exchanged beta zeolites

Zeolite beta, a large-pore zeolite, was investigated in this study with a view to examining it as a potential adsorbent for the removal of aniline from aqueous solutions. Two different metal-loaded zeolites were prepared by exchanging H-beta zeolite (SiO2/Al2O3 = 75:1) with copper. The influence of exchanged copper on the uptake level was assessed. The effect of varying the silica-to-alumina ratio of the H-beta zeolite on the aniline uptake level was also examined, using three different H-beta zeolites with ratios of 25:1, 75:1 and 150:1 as adsorbents. The sorption experiments indicated an uptake level of ca. 110–120 mg/g for each zeolite and this level was also adsorbed by the copper-modified H-beta zeolites (SiO2/Al2O3 = 75:1). In all cases, the adsorption process followed the Langmuir model for adsorption and the level of aniline adsorbed was largely unaffected by a change in temperature or the presence of extra framework copper. The stability of the exchanged copper on these zeolites was then examined by measuring the quantity of copper leached from each zeolite into solution as a function of pH. Minimum copper leaching was observed in the pH range 5–11. This provided a stable pH working range for the adsorbent materials.

An Investigation into the Adsorption Characteristics of Grafted Mesoporous Silicates for the Removal of Tetramethyl Ammonium Hydroxide from Aqueous Solution

Four cubic mesoporous silicates (CMS), one unmodified and three grafted with amine, carboxylic and cyano surface functional groups, were prepared, characterised and compared as adsorbents for tetramethyl ammonium hydroxide (TMAH) from aqueous solution. The adsorption process was studied as a function of molecular size and CMS pore volume. Sorption on the unmodified, cyano- and carboxylic-grafted adsorbents closely followed the Langmuir model while adsorption on the amine-treated silicate conformed to the Freundlich model. A comparison of the adsorbent pore volume and the volume of sorbed TMAH molecules suggested that monolayer sorption occurred, there being some evidence that surface functional groups influenced the adsorption process. The presence or absence of structural order, as defined by X-ray diffraction analysis, had no significant influence on the adsorption, as all materials, both ordered and disordered, had relatively high adsorption capacities.

Utilisation of a Mesoporous Silicate Material for the Removal of Quaternary Ammonium Hydroxides (QAHs) from Aqueous Solution

A cubic mesoporous silicate (CMS) was prepared, characterised and assessed as an adsorbent for quaternary ammonium hydroxides (QAHs) from aqueous solution. The adsorption process was studied as a function of molecular size and CMS pore volume. Sorption closely followed the Langmuir model. A comparison of the CMS pore volume and the volume of the sorbed molecules suggested that monolayer sorption occurred and that the number of molecules sorbed was a function of the size of the quaternary ammonium hydroxide molecule and the threshold area capable of being occupied by this molecule.

Influence of Cation-Exchanged Copper on the Adsorption of Phenol onto Zeolite Beta

The aim of this research was to examine the effect of copper cation-exchanged zeolites on the adsorption uptake of organic pollutants. Two beta zeolites with silica-to-alumina ratios of 25:1 and 150:1 were modified by copper cation exchange and their potential for the removal of phenol from aqueous solutions was investigated. It was found that copper loading could be increased by increasing the pH of the exchange to 7. The exchanged copper was found to be relatively resistant to leaching between 5 and 11. An increase in copper loading or silica content resulted in an increase in the adsorption capacity of the zeolite for phenol. Overall, it was found that the adsorption showed best fit to the generalized Langmuir–Freundlich isotherm model. The adsorption process was exothermic and yielded thermodynamic parameters that were contiguous with phenol adsorption.

Removal of Aniline from Waste Streams Using a Combined Adsorption and Catalytic Oxidation Approach

The focus of the work described was the development of a solid catalytic adsorbent material capable of being regenerated, with the ability of adsorbing aniline from aqueous solution and the subsequent catalytic oxidation of the adsorbed aniline. Initially, an H-ZSM-5 zeolite was loaded with copper via an ion-exchange process to enhance its catalytic activity. Experimental results indicated an aniline adsorption level of ca. 37–42 mg/g for each of the unmodified H-ZSM-5, the 0.5 w/w% Cu–ZSM-5 or the 1.4 w/w% Cu–ZSM-5 zeolites. The Langmuir adsorption model was applicable to all aniline-on-zeolite adsorption processes, with the level of aniline adsorbed being largely unaffected by a change in temperature. The kinetics of the adsorption processes, indicated that the maximum uptake of aniline occurred within 50 min of contact. Assessment of the aqueous stability of the exchanged copper on the ZSM-5 zeolites indicated minimum copper leaching within the pH range 5–11, thus providing a stable working pH range for both the 0.5 w/w% and 1.4 w/w% Cu–ZSM-5 adsorbent materials. Catalytic oxidation studies on the adsorbed aniline indicated that the presence of copper in the zeolites significantly enhanced the degradation of aniline to predominantly carbon dioxide, water and nitrogen, with the production of significantly smaller levels of nitrogen oxide, benzene and nitrogen dioxide.