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Title: Gels of swellable crosslinked polymer colloids for lead removal from water
Author: Mohd Zaki, Syazwani
ISNI:       0000 0005 0290 6508
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2020
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In this thesis, a study of new pH-responsive double-crosslinked microgels/nanogels (DX MGs/ DX NGs) is conducted to investigate the properties and potential for lead (Pb) removal application. The first part of this study is about DX MGs from a new co-monomer, 2-carboxyethyl acrylate (CEA). An improvement in the ductility is desirable for biomaterials application. The ductility improvement of DX MGs with the presence of CEA was evident when compared to established DX MAA (MAA is methacrylic acid) gels (compressive breaking strain, 49.5%). The breaking strain obtained for DX CEA21 and DX CE28 gels were 58.24% and 62.3%. Mechanical properties are important parameter to evaluate the strength of these newly synthesised microgels (MGs) for specific application. Meanwhile, for a blend system (DX BL-CEA) the breaking strain obtained was 61.4%. Interestingly, the swelling behaviour of DX BL-CEA gel was in between that of DX CEA21 and DX CEA28. This behaviour shows that the swelling of the DX CEA gels can be tuned by blending of the two components. The second part of the study is related to DX NG gels prepared using MAA. These MGs/NGs were synthesised by emulsion polymerisation. Thereafter, vinyl groups were introduced to the nanogels (NGs) through functionalisation with glycidyl methacrylate (GMA) by the reaction of carboxylic acid and epoxide group. The formation of DX NGs was obtained by free-radical polymerisation of vinyl groups on the surface of the NGs. The next part is associated with Graphene Oxide (GO) to prepare DX NGs composites with high modulus. Graphene oxide (GO) was exfoliated and well-integrated within the DX NG to produce DX NG/GO composite gels with outstanding mechanical properties. Given that only 0.2 wt.% of GO was present, the values of shear modulus showed remarkable enhancement for DX NG/GO (60.3 kPa) compared with as-made gel, DX NG (10.2 kPa). From compression analysis, modulus values for DX NG/GO and DX NG are 82.4 kPa and 19.6 kPa, respectively. Removal of Pb2+ from water by DX NG/GO hydrogels was investigated and the interaction between GO and NGs was studied. Adsorption isotherms were also constructed. Adsorption isotherms were measured to determine the maximum adsorption capacity of Pb2+ ions by the gels. The physical and mechanical properties of DX NG and DX NG/GO with and without Pb2+ were comprehensively studied to understand the effects of Pb as an additional crosslinker in the network structure of NGs. The effects of contact time and initial concentration of Pb2+ were explored. The maximum adsorption capacity obtained for DX NG/GO and DX NG were 254 ±15 mg/g and 204 ±17 mg/g. The GO role in capturing more Pb2+ ions was confirmed by XPS analysis. The effect Pb2+ uptake on the mechanical properties of the DX NG/GO and DX NG gels was investigated. The compression modulus values obtained for DX NG and DX NG/GO after 1000 ppm Pb uptake are 247 kPa and 336 kPa. For the breaking stress, the values obtained for DX NG and DX NG/GO after Pb uptake are 1045 kPa and 1273 kPa. These values are much higher than the as-made gels before Pb adsorption takes place. It is proposed that the network structure contained additional ionic crosslinker due to Pb2+ ions. The gels have good potential for Pb removal from wastewater. In this work, the main focus of removal is on Pb2+.
Supervisor: Saunders, Brian ; Kinloch, Ian Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Crosslinked microgels ; Crosslinked nanogels ; Lead ion removal ; Microgels ; Pb2+ removal ; Composite ; Graphene oxide ; Hydrogels ; Nanogels ; Heavy metal removal