Kathy Northcott

Synthesis and characterization of hydrophobic zeolite for the treatment of hydrocarbon contaminated ground water

Hydrophobic zeolite was synthesized, modified and characterized for its suitability as a permeable reactive barrier (PRB) material for treatment of hydrocarbons in groundwater. Batch sorption tests were performed along with a number of standard characterization techniques. High and low ionic strength and pH tests were also conducted to determine their impact on hydrocarbon uptake. Further ion exchange tests were conducted to determine the potential for the zeolite to act as both a hydrocarbon capture material and nutrient a delivery system for bioremediation. The zeolite was coated with octadecyltrichlorosilane (C18) to change its surface properties. The results of the surface characterization tests showed that the underlying zeolite structure was largely unaffected by the coating. TGA measurements showed a reactive carbon content of 1-2%. Hydrocarbon (o-xylene and naphthalene) sorption isotherms results compared well with the behaviour of similar materials investigated by other researchers. Ionic strength and pH had little effect on hydrocarbon sorption and the treated zeolite had an ion exchange capacity of 0.3 mequiv./g, indicating it could be utilised as a nutrient source in PRBs. Recycle tests indicated that the zeolite could be used cleaned and reused at least three times without significant reduction in treatment effectiveness.

Adsorption Behavior of Cadmium(II) and Lead(II) on Mesoporous Silicate MCM-41

Abstract This investigation examines metal ion adsorption on mesoporous silicate, MCM‐41, synthesized from sodium silicate solution and cethyltrimethylammonium bromide (CTAB). MCM‐41 has potential as an adsorbent material, with a regular hexagonal pore structure, large specific surface area, and large pore volume. The MCM‐41 synthesized for this investigation is characterized using powder X‐ray diffraction and nitrogen adsorption and desorption isotherms data. The adsorption behavior for cadmium(II) and lead(II) onto MCM‐41 was studied by contacting the mesoporous silicate with an aqueous solution of metal salts and acetylacetone. Both Cd2+ and Pb2+ were found to quantitatively adsorb onto MCM‐41. The results of this study suggest that MCM‐41 may have applications in the recovery of toxic metals from waste waters.

Synthesis and surface modification of mesoporous silicate SBA-15 for the adsorption of metal ions

Abstract In this study surface modified SBA‐15, coated with octadecyltrichlorosilane (C18), is considered as an alternative adsorbent for metal ions in water. The SBA‐C18 was loaded with Bis(2,4,4-trimethylpentyl) phosphinic acid (cyanex 272) as the metal ion extractant. The adsorption characteristics of phosphinic acid loaded SBA‐C18 were evaluated for Cu(II) and Zn(II) ions in aqueous solution. Adsorption tests indicated that a contact time of 1 hour was sufficient for adsorption equilibrium to occur. The pH1/2 values of Zn(II) and Cu(II) onto SBA‐C18, were found to be similar to published data for levextrel ion exchange resins and around 1 pH unit lower than published solvent extraction data for cyanex 272 in xylene.

Water treatment design for site remediation at Casey Station, Antarctica: site characterisation and particle separation

Abstract Antarctica is commonly regarded as a pristine environment, but more than a century of human activity has left an extensive legacy of abandoned waste. The Australian Antarctic Division (AAD) has identified the Thala Valley Tip near Casey Station as a high priority site for remediation. However, there are difficulties with regards to contaminant dispersal by melt-water during extraction of wastes and contaminated sediments. Characterisation of contaminants and other site-specific conditions is crucial when designing appropriate water treatment technologies. Analysis of contaminants in Tip waters has found that heavy metals are predominantly associated with particles, although there are substantial concentrations of dissolved metals as well. The combined chemical and physical analyses indicate that the main heavy metals transport mechanism as adsorption to the surface of particles, which are then carried by surface and sub-surface runoff. To remove heavy metals from contaminated water during the proposed clean-up of Thala Valley a multistage treatment process will be required. The first stage is one of particle removal. A plant has been designed that uses coagulation and flocculation chemicals to produce a fast settling, flocculated suspension. The flocculated particles will settle out in an inclined settler, producing a clarified effluent and a concentrated sludge. The clarified water will then be passed through a 1-μm filter to remove any residual particles prior to dissolved heavy metals removal either by ion exchange or distillation. Future research will focus on optimisation of the water treatment system, especially coagulation and flocculation processes and the impact of pH, turbidity, low temperature and water chemistry on flocculation efficiency.

Synthesis, characterization and evaluation of mesoporous silicates for adsorption of metal ions

Abstract —In this study mesoporous silicates MCM-41 and SBA-15 were investigated for their potential as metal ion-selective adsorbents. The greatest advantage of these materials is their large surface area, uniform pore size and controlled surface chemistry, and hence their potential for adsorption processes. The studies of the adsorption of transition metal ions onto MCM-41 examined the comparative adsorption behavior of Zn(II) and Cu(II), using acetylacetone (Hacac) as a chelating agent. The results showed that the MCM-41/Hacac system has potential as an ion-selective adsorbent material. However, due to the relatively small pore size and potential instability of MCM-41 when immersed in water for long time periods, a second mesoporous silicate, SBA-15, has been investigated. The SBA-15 was coated with octadecyltrichlorosilane (C18), and then loaded with a chelating agent (Cyanex 272) and assessed for its potential as an adsorbent material. The surface-modified SBA-15 has been found to have high metal ion selectivity and extractability, and hence good potential as an alternative to established solvent extraction systems.

From urban municipalities to polar bioremediation: the characterisation and contribution of biogenic minerals for water treatment

Minerals of biological origin have shown significant potential for the separation of contaminants from water worldwide. This study details the contribution of biologically derived minerals to water treatment operations, with a focus on filtration media from urban municipalities and remote cold regions. The results support biofilm-embedded iron and manganese to be the building blocks of biogenic mineral development on activated carbon and nutrient-amended zeolites. The presence of similar iron and manganese oxidising bacterial species across all filter media supports the analogous morphologies of biogenic minerals between sites and suggests that biological water treatment processes may be feasible across a range of climates. This is the first time the stages of biogenic mineral formation have been aligned with comprehensive imaging of the biofilm community and bacterial identification; especially with respect to cold regions. Where biogenic mineral formation occurs on filter media, the potential exists for enhanced adsorption for a range of organic and inorganic contaminants and improved longevity of filter media beyond the adsorption or exchange capacities of the raw material.