Clarkson University Department of Chemical and Biomolecular Engineering Seminar:
pH-Mediated Electrochemical Precipitation of Scaling Ions from Reverse Osmosis Concentrate in Brackish Groundwater Desalination
Sheraz Bashir
Abstract
Rising global water demand has highlighted brackish groundwater reverse osmosis as a promising desalination approach for producing fresh water and alleviating the strain on dwindling drinking water resources. However, this process generates a substantial volume of waste brine—reverse osmosis concentrate (ROC)—whose disposal presents both technical and environmental challenges due to its high concentrations of salts and minerals. To enable more sustainable management of ROC, including its disposal or potential valorization, one effective strategy is to minimize its volume by removing scaling ions (e.g., Ca2+ and Mg2+), enhancing overall water recovery. Although chemical precipitation has shown to be effective in separating these scaling ions, the reliance on chemical reagents—and the associated costs of their transport and storage—continues to limit its large-scale implementation.
This presentation explores electrochemical precipitation as a promising alternative to conventional chemical precipitation methods. A two-compartment electrochemical cell divided by a cation exchange membrane was designed, enabling the selective removal of scaling ions from the ROC feed. Detailed experimental studies revealed that substantial Ca2+ removal occurs at pH levels below 10 (at current densities <20 mA/cm2), while Mg2+ removal becomes prominent at pH levels above 10 (>20 mA/cm2). These trends are further supported by chemical equilibrium model simulations using Visual MINTEQ. Investigations into the influence of a model antiscalant—nitrilotris-methylenephosphonic acid (NTMP)—in synthetic ROC revealed that NTMP inhibited precipitation, particularly at lower current densities, due to its scaling inhibition properties. Furthermore, physical characterization of the precipitated minerals indicated that, although NTMP did not impact the crystalline structure, it markedly affected crystal morphology, transforming well-developed crystals into smaller agglomerates. Collectively, these findings underscore the potential of electrochemical precipitation as a sustainable brine management strategy, advancing water recovery and supporting progress toward achieving zero liquid discharge (ZLD) in desalination.
Monday, 04/21/2025 at 3:00 pm
CAMP 194
https://clarkson.zoom.us/j/95529580049
Sheraz Bashir is a Ph.D. candidate working with Dr. Taeyoung Kim at Clarkson University since Fall 2022. His research focuses on electrochemical separations for valuable resource recovery from geothermal and desalination brine. Before joining Clarkson University, he graduated with a BS and MS degrees in Chemical Engineering from the University of the Punjab (Pakistan) and King Fahd University of Petroleum and Minerals (Saudi Arabia).