Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 145064

145064 - Advancements in Hypersaline Wastewater Treatment: The Promise of Quasi-Liquid Surfaces to Reduce Salt Scaling 

Desalination is increasingly recognized as a viable solution to the global freshwater shortage, with seawater as its primary source. The rapid expansion of desalination plants has led to the production of large volumes of hypersaline brine, which poses severe threats to aquatic ecosystems and public health when improperly disposed of. Additionally, the valuable salts contained within this brine represent a significant economic opportunity if recovered. The concept of Zero Liquid Discharge (ZLD) desalination has emerged as a promising approach to address these issues, aiming to eliminate waste liquid while producing salt byproducts and clean water. Despite its potential, the efficiency of current ZLD systems, which rely heavily on membrane-based technology for preconcentration and salt crystallization through brine crystallizers or evaporation ponds, is hindered by high energy consumption and low solar energy efficiency, respectively. Evaporation-based zero liquid discharge (ZLD) desalination offers significant potential in treating highly saline wastewater. Yet, the accumulation of salt on evaporation surfaces can disrupt the desalination process's efficiency and ongoing operation.

In this investigation, we present an approach employing a Quasi-Liquid Surface (QLS) designed to exhibit ultralow adhesion to salt aggregates after evaporation by influencing the crystallization process. This study focuses on the evaporation dynamics of hypersaline brine droplets on the QLS under conditions equivalent to 1 sun illumination, aiming to discern the pattern of evaporation and crystal nucleation. Our findings demonstrate that the presence of a flexible polymer brush layer significantly reduces adhesion to salt crystals to less than 10 mN mg⁻¹, a value considerably lower than the adhesion observed on a standard silicon substrate (0.19 N mg⁻¹).

The rationale behind the reduced adhesion and efficient salt management is twofold: (i) The QLS's ultra-smooth surface introduces a significant barrier to nucleation. As evaporation proceeds, salt nucleation is preferentially initiated at the brine-air interface rather than directly on the substrate. This effect, combined with the substrate's slippery characteristic, encourages the inward migration of salt nuclei, leading to the formation of dense, compact salt crystals. (ii) Towards the end of the evaporation process, it is proposed that the brine solution withdraws from the QLS, minimizing points of contact through the contraction of the liquid bridges. Introducing a gentle airflow facilitates the effortless detachment of salt crystals from the QLS.

Additionally, we explored the evaporation behavior of hypersaline droplets on other surfaces, including polyethylene glycol (PEG)—a hydrophilic surface with slippery properties and bare silicon substrates, to draw comparisons and better understand the impact of surface characteristics on evaporation dynamics. The findings indicate that the strategy of mobility-induced crystallization promoted by the QLS holds promise as an effective method for treating hypersaline wastewater, aligning with Zero Liquid Discharge (ZLD) principles. This investigation highlights the potential of the QLS in contributing to the sustainable management of hypersaline wastewater, representing a significant advancement in environmental sustainability and water resource preservation efforts.

Presenting Author: Mohammed Imran Khan Michigan State Univeristy

Presenting Author Biography: Mohammed Imran Khan is currently pursuing a PhD in Mechanical Engineering at Michigan
State University, where he is dedicated to pushing the boundaries of his field through
meticulous research. His academic journey is fueled by a keen interest in surface modifications,
droplet dynamics, polymer brush surfaces, and the management of hypersaline brine. These
focal areas, pivotal for technological innovation and environmental preservation, enable him to
delve into developing sustainable solutions to complex engineering problems.

Authors:

Mohammed Imran Khan Michigan State Univeristy
Bei Fan Michigan State University