Date of Graduation

5-2026

Document Type

Thesis

Degree Name

Bachelor of Science in Chemical Engineering

Degree Level

Undergraduate

Department

Chemical Engineering

Advisor/Mentor

Ranil Wickramasinghe

Committee Member

Ranil Wickramasinghe

Second Committee Member

Heather Walker

Third Committee Member

Tom Spicer

Abstract

This research evaluates the effectiveness of polymeric inhibitors at suppressing scaling during direct contact membrane distillation (DCMD). Anionic polyacrylic acid (PAA), neutral polyethylene glycol (PEG), and cationic polyethyleneimine (PEI), were investigated. Experiments were conducted using both hypersaline single-salt and multi-component mixed-salt feeds to determine how the presence of different ions influences performance. Results from single-salt experiments showed that PAA and PEG effectively maintained permeate flux through chelation and steric hindrance, respectively, while PEI caused rapid membrane failure due to interfacial aggregation and pore wetting. In complex mixed-salt solutions, PEG was the additive, maintaining a steady flux with only a 7.33% decline. Its success is attributed to its non-ionic nature, which avoids the "charge shielding" and competitive adsorption that compromised the ionic inhibitors. These findings suggest that neutral, steric-based inhibition strategies could be effective for the high-recovery treatment of diverse industrial brines.

Keywords

Direct Contact Membrane Distillation (DCMD); Scaling; Charge; Antiscalant; Hypersaline Brines

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