Sulfur Copolymers via Emulsion Polymerization

Abstract

This study was conducted to develop sulfur composites using emulsion polymerization, presenting a novel, rapid, and straightforward method for creating sulfur emulsions, particularly for applications in wastewater treatment. The emulsion polymerization technique addresses challenges related to heat and mass transfer, overcoming limitations observed in alternative polymerization methods, such as inverse vulcanization. Various analytical techniques, including XRD, FTIR, SEM, optical microscopy, viscometer, dynamic light scattering, and TGA, were employed to investigate and validate the formation of the sulfur-emulsion composite. XRD results confirm the complete conversion of crystalline sulfur to an amorphous form, while FTIR indicates reaction completion and the presence of amide bond stretching. SEM, TEM, and optical microscopy were utilized for a precise characterization of particle formation in the emulsion, facilitating a thorough morphological analysis. TGA analysis reveals that the prepared sulfur composite lacks robust thermal properties, even at elevated sulfur concentrations. The application of ANOVA response surface methodology elucidates the impacts of various factors on emulsion droplet size, density, and viscosity. Different sulfur concentrations ranging from 0-40% were chosen for emulsion preparation to analyze the sulfur's effect. Interestingly, at sulfur concentrations up to 30%, sulfur is completely dissolved in the emulsion, maintaining a stable density (1.1 g/cm³), droplet size (260 nm), and dynamic viscosity (4.7 mPa.s). However, as the sulfur concentration increases to 40%, the sulfur emulsion-based composites lose their amorphous behavior due to the presence of unreacted sulfur particles, as confirmed by ANOVA simulations. This comprehensive study provides valuable insights into the emulsion polymerization of sulfur and its potential applications, particularly highlighting the optimal sulfur concentration for maintaining desired properties in the composite material.

To extend the application of the sulfur copolymers prepared through emulsion polymerization, we conducted a comprehensive study focused on the removal of lead metal ions from wastewater. This investigation emphasizes the stability of sulfur emulsions to optimize the extraction of heavy metal ions, particularly lead, from aqueous solutions. The prepared emulsion copolymers are composed of sulfur as a carrier, ethylene diamine as an organic solvent, span 80 as an emulsifying agent, and sulfuric acid as the stripping phase. Key factors considered for ensuring emulsion stability and maximizing the removal of heavy metals include the concentration of sulfur (ranging from 0-40% v/v), span 80 (2-12% v/v), stripping phase (0.5-2 M H2SO4), emulsification speed (200-800 rpm), emulsification time (5-30 min), and the volume ratio of the organic phase to the stripping phase (1-3). The results demonstrate that sulfur emulsion copolymers can effectively remove lead ions from wastewater, achieving up to 93% removal at the optimum operating conditions. The successful removal of lead ions was confirmed through the use of an Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) instrument, ensuring accurate analysis.

Moreover, we have also explore the computational fluid dynamic analysis of heavy metal ions adsorption from wastewater using inversed-vulcanized porous sulfur copolymers. Two inverse-vulcanized sulfur copolymer foams reported previously were selected for this study. These foams were prepared using poly (sodium 4-styrene sulfonate) and sodium chloride as porogens. The CFD model results are validated with the experimental results at fixed and varied operational conditions. The inverse-vulcanized sulfur copolymer foams prepared by using the poly (sodium 4-styrene sulfonate) commoner present high porosity (59.09%), less density (0.53 g/cm3), and smaller particle size (20–50 μm). Two and three-parameter isothermal models are used to describe the adsorption behavior of metals. Remarkably, the adsorption process has been explained for the position of the material through CFD modeling. The hydrodynamics of wastewater has been demonstrated by considering the laminar flow porous zone model for metal ion adsorption under the independent grid process. Various heavy metals removal such as arsenic, mercury, cadmium, and lead scrutinized by porous sulfur copolymers. This approach provides an excellent idea to present the theoretical analysis of metal ions adsorption through sulfur-based polymers and validate their results. It can save time, predict the closest results to experiments, and scale up lab processes to an industrial level. The CFD modeling uses the viscous laminar flow model at a low Reynolds number. The adsorption efficiency of heavy metals varied between 60-85%. In the case of PSSD, the observed adsorption trend is: As > Cd > Hg > Pb.

Date of Award	25 Dec 2023
Original language	American English
Supervisor	Saeed Alhassan (Supervisor)