Determining the operational window of green antiscalants: a case study for calcium sulfate

Abstract

The detrimental effects of inorganic scaling in industrial and domestic applications are often mitigated with scale inhibitors. Increasing environmental awareness and stringent regulations require developing more sustainable antiscalants. Testing of suitable candidates is often the rate-limiting step in development cycles, therefore we developed a high-throughput methodology to rapidly evaluate the antiscaling potential of new additives under different application conditions. Using this method we determined the performance of two potential green additives – a chelating agent and a threshold inhibitor – in delaying CaSO4 precipitation over a wide range of supersaturations, temperatures and salinities. The threshold inhibitor strongly delayed CaSO4 scaling, but its performance is highly dependent on the physicochemical conditions, with the appropriate application window comprising low salinities and mild temperatures. In contrast, the chelating agent showed a lower inhibiting capacity, but its performance remained relatively constant throughout the entire matrix of physicochemical conditions. Noteworthy, we also observed that at intermediate salinities the absolute induction time for CaSO4 precipitation is dramatically prolonged, offering a sustainable strategy to mitigate scaling. Overall, our method allows simultaneously benchmarking the scaling kinetics and testing the scale-inhibiting performance of additives, providing a direct route to a more rational design of antiscaling technologies.