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- Mustafa, Majid, 1987-
(författare)
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Removal of Micropollutants from Wastewater : evaluation of effect of upgrading ozonation to electro-peroxone
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The United Nations (UN) has adopted 17 “Sustainable Development Goals” (SDGs) to achieve a clean, better and sustainable future. SDG 6 is to ensure that everyone has access to clean water and sanitation by 2030. According to the UN Educational, Scientific and Cultural Organization (UNESCO), more than 80% of wastewater produced from human actions is discharged into rivers or seas without any pollution removal. Thus, the presence of micropollutants (MPs: including, inter alia, pharmaceuticals, biocides and personal care products) in wastewaters is a major challenge that poses potential threats not only to aquatic system but also to humans due to their potential toxicity and potential to induce antibiotic resistance. Wastewater treatment plants (WWTPs) are considered hotspots for release of MPs as the current treatment processes are not designed to remove them. This thesis is based on studies described in four appended papers (Papers I-IV) designed to help efforts to solve these problems by investigating the factors involved and developing advanced treatment processes for removing MPs.Ozonation is one of the most intensively studied and widely used advanced treatment processes for removing MPs. However, due to ozone’s (O3) chemical selectivity, it cannot remove resistant MPs so its use (without additional treatments) results in their release into the environment. Thus, key objectives were to evaluate effects of switching to a new emerging process called electro-peroxone (E-peroxone) on MPs’ removal, by inserting two electrodes into an ozonation reactor. Its potential utility for other applications were also investigated.Paper I addresses effects of upgrading from ozonation to E-peroxone on pharmaceuticals’ removal at lab-scale, using a quantitative structure-activity relationship (QSAR) model. For this purpose, the relationship between QSAR model-predicted second-order rate constants of ozone’s reactions with pharmaceuticals (kO3 values) and ratios of experimentally determined pseudo-first order rate constants of E-peroxone and ozonation (kEP/kOZ values) was examined. Results showed that E-peroxone accelerated the removal of O3-resistant pharmaceuticals. In addition, the QSAR model predicted kO3 values for 491 pharmaceuticals, which suggested that large numbers of pharmaceuticals have high O3 resistance. Paper II addresses the removal of antimicrobials, including biocides and antibiotics, by E-peroxone and ozonation in relation to the water matrix. The results indicated that all studied antibiotics were effectively removed by both processes. In contrast, most of the biocides were at most moderately reactive with ozone, so their removal rate by ozonation was lower. The E-peroxone process increased their removal rate (i.e. removed them much more rapidly) by enhancing formation of hydroxyl radicals (•OH). Paper III reports the design, construction and tests of a pilot-scale mobile E-peroxone and ozonation system for removing naturally occurring MPs in secondary wastewater effluents. The tests included assessments of a new, scalable graphene modified carbon brush cathode for the E-peroxone process, which was found to enhance removal of moderately O3-reactive MPs significantly, and O3-resistant MPs moderately, while consuming similar amounts of electrical energy, or even less, for removing most of the MPs used in the experiments. Paper IV describes the regeneration of spent activated carbon, used for removing ionic MPs, by E-peroxone and ozonation. Both processes restored the activated carbon’s sorption efficiency to similar (or even higher) levels than that of virgin activated carbon, for all tested MPs except perfluorooctanoic acid (PFOA). It was concluded that sorption of MPs on regenerated activated carbon is mainly driven by interactions between ionic forms of the MPs with activated carbon’s charged surfaces rather than their interactions with pores in the activated carbon.
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| 2. |
- Nelson, Hanna, 1976-
(författare)
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Modelling precipitation and surface complexation reactions in systems with Goethite, Cu(II) and Oxyanions Containing As(V) or P(V)
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aqueous solubility of oxyanion (e.g. phosphates and arsenates), and thereby their mobility, bioavailability (phosphates) and toxicity (arsenates), in soils and sediments is dependent upon their chemical speciation. In complex, multicomponent systems, equilibrium modelling can be a useful tool to predict chemical speciation. When establishing a model, it is essential to understand the interactions between all the components not only in solution but also on mineral surfaces at a molecular level. By applying surface complexation models processes at mineral surfaces can be accounted for. This thesis is a summary of four papers and focuses on surface complexation of the oxyanions arsenate, phosphate and monomethyl phosphate adsorbed onto the surface of goethite (α-FeOOH). Furthermore, adsorption and precipitation of copper(II) arsenates from aqueous solutions has been studied. Solid copper(II) arsenates obtained in precipitation experiments were characterised and five different solid phases with different Cu(II) to As(V) ratio, as well as proton and Na +content, were identified; Cu5Na(HAsO4)(AsO4)3(s), Cu5Na2(AsO4)4(s), Cu3(AsO4)2(s), Cu3(AsO4)(OH)3(s) and Cu2(AsO4)(OH)(s). The adsorption of arsenate and copper(II) to the goethite surface, could not be predicted by only applying the combined model from the two binary systems, arsenate-goethite and copper(II)-goethite. Instead, two ternary copper-arsenate-goethite surface complexes were added. In one of the surface complexes arsenate is bound to goethite surface via a copper(II) ion coordinating to surface hydroxyl groups and in the other surface complex, copper(II) is coordinating arsenate bound to the goethite surface. Surface complexation models, in agreement with macroscopic data and detailed spectroscopic results, were designed for monomethyl phosphate, phosphate and arsenate adsorbed to goethite. The models contain monodentate inner sphere surface complexes stabilized by hydrogen bonding to neighbouring surface sites. The charge distribution of the complexes was assigned according to Pauling’s valence bond theory. The monomethyl phosphate model consists of three singly protonated surface isomers, only differentiated by the location of the proton . In the case of phosphate and arsenate, six surface complexes, including two pair-wise surface isomers, are suggested to form; ≡FeOAsO 32.5-; (≡FeOAsO3; ≡Fe3OH)2-;(≡FeOAsO3H; ≡Fe3O)2-; (≡FeOAsO3H; ≡Fe3OH)1-; (≡FeOAsO3H2; ≡Fe3O)1- and ≡FeOAsO3H20.5-. A combination of structural information from spectroscopic measurements and quantitative data from spectroscopy, potentiometry and adsorption experiments provides a better understanding of the complexity of the coordination chemistry of particle surfaces and forms the basis for equilibrium models with high physical/chemical relevance.
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