Bioflocculants are flocculating substances produced by microorganisms during growth and have recently received considerable attention from researchers; due to their biodegradability, non-toxicity and lack of secondary pollution from degradation intermediates. This study evaluated the efficiency of bioflocculant produced by Bacillus sp. AEMREG4 isolated from Tyhume River. The bacterial identification was through 16S rDNA sequencing; nucleotide sequences were deposited in GenBank as Bacillus sp. AEMREG4 with an Accession number KP406729. The optimum culture conditions for bioflocculant production were an inoculum size of 4 percent (v/v) and starch as well as yeast extract as sole carbon and nitrogen sources respectively. The addition of CaCl2 enhanced the flocculating activity, at a wide range of pH 4-10 and the highest flocculating activity was reached at an initial pH 8 (80 percent). A bioflocculant yield of 0.78 g was recovered from 1 L of culture broth. The optimum flocculating activity of 78 percent was reached at the lowest bioflocculant dosage of 0.1 mg/ml and the presence of divalent cations (Ca2+, Mn2+ and Mg2+) as well as a trivalent cation (Al3+) enhanced flocculating activity. The purified bioflocculant retained more than 70 percent flocculating activity when subjected to heating at 100 °C for 1 h and maximum flocculating activity of 83 percent was achieved at both acidic and basic pH values of 3 and 10 respectively. Chemical analysis showed that the bioflocculant is predominantly polysaccharide. The Fourier transform infrared (FTIR) spectrum revealed the presence of carboxyl, hydroxyl and methoxyl groups as the functional moieties and the scanning electron microscopy (SEM) imaging of the purified bioflocculant showed its morphological structure as rod-shaped which contributes to its high flocculating efficiency. The high flocculation activity displayed by this bioflocculant indicates its potential suitability for industrial application.

Bioflocculants are flocculating substances produced by microorganisms during growth and have recently received considerable attention from researchers; due to their biodegradability, non-toxicity and lack of secondary pollution from degradation intermediates. This study evaluated the efficiency of bioflocculant produced by Bacillus sp. AEMREG4 isolated from Tyhume River. The bacterial identification was through 16S rDNA sequencing; nucleotide sequences were deposited in GenBank as Bacillus sp. AEMREG4 with an Accession number KP406729. The optimum culture conditions for bioflocculant production were an inoculum size of 4% (v/v) and starch as well as yeast extract as sole carbon and nitrogen sources respectively. The addition of CaCl2 enhanced the flocculating activity, at a wide range of pH 4-10 and the highest flocculating activity was reached at an initial pH 8 (80%). A bioflocculant yield of 0.78 g was recovered from 1 L of culture broth. The optimum flocculating activity of 78% was reached at the lowest bioflocculant dosage of 0.1 mg/ml and the presence of divalent cations (Ca2+, Mn2+ and Mg2+) as well as a trivalent cation (Al3+) enhanced flocculating activity. The purified bioflocculant retained more than 70% flocculating activity when subjected to heating at 100 °C for 1 h and maximum flocculating activity of 83% was achieved at both acidic and basic pH values of 3 and 10 respectively. Chemical analysis showed that the bioflocculant is predominantly polysaccharide. The Fourier transform infrared (FTIR) spectrum revealed the presence of carboxyl, hydroxyl and methoxyl groups as the functional moieties and the scanning electron microscopy (SEM) imaging of the purified bioflocculant showed its morphological structure as rod-shaped which contributes to its high flocculating efficiency. The high flocculation activity displayed by this bioflocculant indicates its potential suitability for industrial application.Keywords: Bioflocculant, Bacillus sp. AEMREG4, flocculating activity.

Polyacrylamide is widely used as a flocculant but the influence of the molecular mass distribution upon flocculant activity is poorly understood. This thesis outlines the successful characterisation of ultrahigh molecular mass polyacrylamide solutions in terms of discrete solvated polymer coils and coil agglomerates. These features were correlated with the observed flocculation, demonstrating a number of solution state features required to improve flocculation activity.Aqueous solutions of polyacrylamide exhibit time-dependant behaviour affecting viscosity and polymer agglomeration. Improving the solvation of the polymer suppressed the agglomerates, as did manipulation of hydrogen bonding through the presence of salts. Limiting agglomeration through improved solvation apparently lowers a barrier to polymer interaction, such that the coils disperse but become more susceptible to reagglomeration under mild shear. These solvent modifications did not fully suppress the agglomerates.To fractionate polyacrylamide into a molecular mass distribution, flow field-flow fractionation (flow FFF) was chosen, coupled to a multi-angle laser light scattering (MALLS) photometer and a differential refractometer for molecular mass and concentration sensitive detection, respectively. For the first time, the analysis of high molecular mass polyacrylamides in water using the flow FFF-MALLS technique has been reported. However, a number of difficulties needed to be overcome, including shear artefacts, sample agglomeration and polymer-membrane interactions.Both polyacrylamide standards and commercial flocculants were amenable to the technique. Commercial flocculants were found to vary not only with regard to viscosity and mean molecular mass, but also with sub- and supramicron size agglomerates. The flow FFF technique is size-sensitive, which for some low molecular mass samples displayed an ++ / unusually wide elution profile, in apparent conflict with the molecular mass sensitive MALLS detector. It was concluded that polyacrylamide in solution exists simultaneously in three states: discrete polymer coils, entanglements of a several coils, and agglomerates with supramicron diameters.This thesis concluded with a comparison between the characterised polyacrylamides and observed flocculation activity on a standard kaolin substrate. Results show polymer with supramicron agglomerates produce the largest and most shear-resistant kaolin aggregates with a definite optimum agitation intensity. Higher molecular mass flocculants with less agglomeration bind fine particles under more gentle conditions but are deficient under increasing stress. Flocculants exhibiting coil entanglements showed poor activity and formed only small aggregates. A modified flocculation mechanism was proposed, in which supramicron polymer agglomerates play a critical role.

No description available.

No description available.

No description available.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 112-114).

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The performance of flocculants used in the solid-liquid separation of red mud is often compromised by the methods used to mix the fast acting polymers into the slurry. A simple model of the relationship between flocculant performance and intensity of mixing is proposed and a device for mixing flocculant and slurry has been developed on the basis of the model.The intensity of mixing at the point of distributing the flocculant into the slurry is arguably the most important variable influencing the final flocculant performance. This relationship is established using data from flocculation tests in an agitated tank. The flocculant performance is monitored using an optical sensor and the settling rate of the solid-liquid interface is used as a comparison for the optical sensor. The difficulties, errors and merits of the optical sensor to study the flocculation of red mud and automatic control of flocculation processes are also assessed.The mixing device is connected to a pipe for flocculation tests with red mud. For the tests carried out, a high level of flocculation was recorded.The mixing device combines the flocculant and slurry as thin annular jets directed into one another. The opening for the slurry jet can be altered to provide a variation of the mixing that is achieved. The capability of the device to mix rapidly has been assessed using the diazo coupling reactions between l-naphthol and diazotised sulphanilic acid in alkaline, aqueous solution at room temperature. Variables studied included flow rate and slurry jet opening. Better mixing was indicated at higher flow rates and at reduced jet opening. The use of the diazo coupling reactions for studying micromixing is also assessed.