title: Construction and demolition waste as low-cost materials for the removal of heavy metal ions from wastewater

authors: Ranaweera, Kavitha H.

abstract: Water pollution due to heavy metal ion contaminations and management of construction and demolition waste (CDW) are two major environmental issues faced by the world today. Exposure to heavy metal ions can cause serious health problems, and therefore, treatment of heavy metal contaminated water/wastewater to protect the environment and people is essential. The management of CDW has become a serious problem due to the large amounts generated each year. Only a small percentage of this waste is recycled, while the majority is disposed of in landfills with space running out to accommodate these materials. Repurposing CDW as low-cost materials for heavy metal ion treatment is thus a promising strategy as this not only contributes to CDW management but also to heavy metal ion remediation.
The research described in this thesis investigated the applicability of five CDW materials (particle board wood dust (PBW), medium density fiberboard (MDF) fines, biochar derived from particle board offcuts (PBB), Gibraltar board fines (GBF), and demolished concrete (DC)) for the treatment of Cd(II), Cu(II), Pb(II), and Zn(II) ions. The selected CDW materials were characterized by performing FTIR, SEM-EDX, TGA, XRD, and surface area analysis to identify the composition and nature of these materials. The effect of different parameters (metal ion type, contact time, initial metal ion concentration, pH, and material dosage) on the heavy metal ion removal process was investigated in single metal ion solution systems utilizing a batch method. All studied materials exhibited high removal efficiency for Pb(II) ions compared to the other metal ions except DC, which showed high removal efficiency towards Cu(II) ions. Therefore, Pb(II) was selected to evaluate the effect of other parameters for PBW, MDF fines, PBB, and GBF, whilst Cu(II) was used for DC. The results indicated that the main heavy metal ion removal mechanism of PBW, MDF fines, and PBB was adsorption, while DC and GBF utilized precipitation. The effect of competitive metal ions on the heavy metal ion removal
process was investigated using a Cd(II)-Cu(II) multi-metal ion system for DC and a Cd(II)-Pb(II) multi-metal ion system for other materials using a batch method. The results indicated that the presence of Cd(II) ions reduced Pb(II) ion removal efficiency for PBW, MDF fines, and PBB and Cu(II) ion removal efficiency of DC. However, Pb(II) ion removal by GBF was not affected. Experiments were carried out to investigate whether the selected CDW materials leached out any toxic substances. The results indicated that PBW and MDF fines increased TOC concentrations, while GBF increased calcium and sulfate concentrations in treated water.
Adsorption isothermal, kinetic, and adsorbent regeneration studies were carried out for CDW materials which utilized adsorption for the heavy metal ion removal. Adsorption isothermal studies were performed for single metal ion systems, and the Freundlich isotherm model fitted better with the experimental data of all studied materials. Adsorption kinetics of both single and multi-metal ion systems were evaluated, and the experimental data fitted better with either pseudo-second-order or Elovich kinetic models for all studied systems. The adsorbent regeneration studies were performed using 0.1 M HCl as a regeneration agent for three adsorption-desorption cycles for both metal ion systems. High % desorption values were obtained during the first cycle, however, the adsorption capacity was reduced in the subsequent cycles for all studied adsorption systems.
Column analyses were conducted for GBF and PBB for both single (Pb(II)) and multi-metal ion systems (Cd(II)-Pb(II)). High % removal values were obtained for Pb(II) ions in both metal ion systems for both materials. The experimental data of the PBB was fitted to column adsorption models as PBB utilized adsorption for heavy metal ion removal, and the Yan model fitted well with the experimental data of both metal ion systems. The results indicate that CDW materials have potential for heavy metal ion treatment. Further research is required to investigate the applicability of these materials in real-world applications.

text: Construction and demolition waste as low-cost materials for the removal of heavy metal ions from wastewater Water pollution due to heavy metal ion contaminations and management of construction and demolition waste (CDW) are two major environmental issues faced by the world today. Exposure to heavy metal ions can cause serious health problems, and therefore, treatment of heavy metal contaminated water/wastewater to protect the environment and people is essential. The management of CDW has become a serious problem due to the large amounts generated each year. Only a small percentage of this waste is recycled, while the majority is disposed of in landfills with space running out to accommodate these materials. Repurposing CDW as low-cost materials for heavy metal ion treatment is thus a promising strategy as this not only contributes to CDW management but also to heavy metal ion remediation.
The research described in this thesis investigated the applicability of five CDW materials (particle board wood dust (PBW), medium density fiberboard (MDF) fines, biochar derived from particle board offcuts (PBB), Gibraltar board fines (GBF), and demolished concrete (DC)) for the treatment of Cd(II), Cu(II), Pb(II), and Zn(II) ions. The selected CDW materials were characterized by performing FTIR, SEM-EDX, TGA, XRD, and surface area analysis to identify the composition and nature of these materials. The effect of different parameters (metal ion type, contact time, initial metal ion concentration, pH, and material dosage) on the heavy metal ion removal process was investigated in single metal ion solution systems utilizing a batch method. All studied materials exhibited high removal efficiency for Pb(II) ions compared to the other metal ions except DC, which showed high removal efficiency towards Cu(II) ions. Therefore, Pb(II) was selected to evaluate the effect of other parameters for PBW, MDF fines, PBB, and GBF, whilst Cu(II) was used for DC. The results indicated that the main heavy metal ion removal mechanism of PBW, MDF fines, and PBB was adsorption, while DC and GBF utilized precipitation. The effect of competitive metal ions on the heavy metal ion removal
process was investigated using a Cd(II)-Cu(II) multi-metal ion system for DC and a Cd(II)-Pb(II) multi-metal ion system for other materials using a batch method. The results indicated that the presence of Cd(II) ions reduced Pb(II) ion removal efficiency for PBW, MDF fines, and PBB and Cu(II) ion removal efficiency of DC. However, Pb(II) ion removal by GBF was not affected. Experiments were carried out to investigate whether the selected CDW materials leached out any toxic substances. The results indicated that PBW and MDF fines increased TOC concentrations, while GBF increased calcium and sulfate concentrations in treated water.
Adsorption isothermal, kinetic, and adsorbent regeneration studies were carried out for CDW materials which utilized adsorption for the heavy metal ion removal. Adsorption isothermal studies were performed for single metal ion systems, and the Freundlich isotherm model fitted better with the experimental data of all studied materials. Adsorption kinetics of both single and multi-metal ion systems were evaluated, and the experimental data fitted better with either pseudo-second-order or Elovich kinetic models for all studied systems. The adsorbent regeneration studies were performed using 0.1 M HCl as a regeneration agent for three adsorption-desorption cycles for both metal ion systems. High % desorption values were obtained during the first cycle, however, the adsorption capacity was reduced in the subsequent cycles for all studied adsorption systems.
Column analyses were conducted for GBF and PBB for both single (Pb(II)) and multi-metal ion systems (Cd(II)-Pb(II)). High % removal values were obtained for Pb(II) ions in both metal ion systems for both materials. The experimental data of the PBB was fitted to column adsorption models as PBB utilized adsorption for heavy metal ion removal, and the Yan model fitted well with the experimental data of both metal ion systems. The results indicate that CDW materials have potential for heavy metal ion treatment. Further research is required to investigate the applicability of these materials in real-world applications.

year: 2024

title: Measuring inter-indexer consistency using a thesaurus

authors: Medelyan, Olena

subjects: computer science

abstract: When professional indexers independently assign terms to a given document, the term sets generally differ between indexers. Studies of inter-indexer consistency measure the percentage of matching index terms, but none of them consider the semantic relationships that exist amongst these terms. We propose to represent multiple-indexers data in a vector space and use the cosine metric as a new consistency measure that can be extended by semantic relations between index terms. We believe that this new measure is more accurate and realistic than existing ones and therefore more suitable for evaluation of automatically extracted index terms.

text: Measuring inter-indexer consistency using a thesaurus When professional indexers independently assign terms to a given document, the term sets generally differ between indexers. Studies of inter-indexer consistency measure the percentage of matching index terms, but none of them consider the semantic relationships that exist amongst these terms. We propose to represent multiple-indexers data in a vector space and use the cosine metric as a new consistency measure that can be extended by semantic relations between index terms. We believe that this new measure is more accurate and realistic than existing ones and therefore more suitable for evaluation of automatically extracted index terms.

year: 2006

title: Self-decolonisation in Aotearoa: Pushing through programmatic Pākehā paralysis

authors: Weijers, Dan M.

abstract: Te reo, tīkanga, mātauranga, te Ao, and kaupapa Māori are finally seeing a resurgence in Aotearoa. This revitalisation is occurring in the tertiary education sector, but staff and skill deficits are holding back many academic disciplines. This chapter documents the challenges facing a traditionally colonial tertiary programme—philosophy— attempting to de-colonise itself. The overlapping nature of the challenges can make decolonising appear to be so difficult that some programmes may feel paralysed. This chapter argues that the importance of decolonisation requires that programmes push through any paralysis they may be experiencing by prioritising decolonisation above other goals.

text: Self-decolonisation in Aotearoa: Pushing through programmatic Pākehā paralysis Te reo, tīkanga, mātauranga, te Ao, and kaupapa Māori are finally seeing a resurgence in Aotearoa. This revitalisation is occurring in the tertiary education sector, but staff and skill deficits are holding back many academic disciplines. This chapter documents the challenges facing a traditionally colonial tertiary programme—philosophy— attempting to de-colonise itself. The overlapping nature of the challenges can make decolonising appear to be so difficult that some programmes may feel paralysed. This chapter argues that the importance of decolonisation requires that programmes push through any paralysis they may be experiencing by prioritising decolonisation above other goals.

year: 2024