Overview

My PhD research focused on developing a fundamental understanding of gypsum heterogeneous crystallization in reverse osmosis treatment. Crystallization is an ordered process that has been modeled for many years, yet many industrial systems continue to lack innovative approaches to prevent nucleation and precipitation of sparingly soluble salts on surfaces.

Groundwater and industrial waters have a high potential to precipitate due to high concentration of sulfates and silica.  Hence, elucidating the mechanism by which gypsum crystals can be prevented from forming, has the potential to benefit technologies in various fields of water treatment.

As industries are looking to reduce their footprint by applying zero liquid discharge targets, and water demands continue to increase from municipalities and the oil and gas industry, a need exists to expand the treating capabilities of our operating systems with regard to managing high salinity feedwaters.

Desalination offers an alternative that many communities must take advantage of. Improving the quality of membrane processes must be approached from both a systems and materials point of view.  In other words, besides implementing energy recovery devices and process optimization, we must continue to seek membrane chemistries that maximize system performance.

Specifics

The membrane at the core of my time at Yale is a dense thin-film composite membrane composed of the typical polysulfone support with a thin polyamide active layer.  During my first two years I worked with various commercial forward osmosis membranes, and the last two years with seawater and brackish water reverse osmosis membranes.

Reverse Osmosis: A well-established technology which could still benefit of some fundamental knowledge on gypsum scaling

I have tested commercial brackish water membranes in our bench scale system with various synthetic feedwater concentrations ranging from 1,000 ppm to 8,000 ppm. In this study, our focus has been placed in the experimental design to be able to obtain kinetics data, and a clear distinction between crystal formation from the bulk or from nucleation on the membrane surface.

Being in a research laboratory has been an exciting opportunity. Considering forces at the nanoscale and at the molecular level is astonishing.  One of my research goals was to design self-assembled monolayers to test gypsum nucleation affinity to various surface chemistries.  I was trained to work in a cleanroom since our materials synthesis protocol required a low level of impurities in the environment to prevent contamination of these model surfaces.

My work in the laboratory involves a number of duties including wet chemistry in the hood, and with some equipment such as atomic force microscopy, dynamic light scattering, scanning electron microscopy, and X-Ray Photoelectron Spectroscopy (XPS), among others.

During my first two years at Yale I tested a forward osmosis bench scale system.  I explored the antifouling behavior of various surface-modified commercial forward osmosis membranes.  We verified the feasibility of various membrane surface modifications to reduce organic fouling when challenged with effluent of synthetic secondary wastewater.  The surface modifications varied from nanomaterials to block copolymers.