Innovative Mineral–Hydrogel Composites for Effective Nutrient Removal to Reduce Harmful Algal Blooms and to Upcycle Nutrients

Harmful algal blooms (HABs) pose significant threats to industries such as fisheries and tourism and also impact public health through the production of cyanobacterial toxins. To address the escalating concerns associated with HABs, we have developed novel calcium alginate hydrogel composites seeded with various minerals to effectively remove and recover phosphorus (P) and nitrogen (N). In this talk, I will present three distinct mineral–hydrogel composites designed to tackle nutrient-enriched wastewater, particularly from municipal sources. First, calcium alginate (Ca-Alg) combined with calcium phosphate (CaP) effectively captures P. Second, composites incorporating both CaP and calcium silicate-based mineral seeds (Ca-Alg/CaP+Wollastonite (CaSiO3)) show enhanced P removal and recovery even under low saturation conditions. Third, composites seeded with nanoscale struvite minerals (Ca-Alg /CaP+Struvite (NH4MgPO4·6H2O)) simultaneously mitigate P and N (ammonia) levels in water. The inclusion of nanoscale mineral seeds reduces the nucleation energy barrier and promotes heterogeneous nucleation, leading to increased mineral formation and nutrient recovery. The hydrogel matrix creates locally higher saturation conditions for CaP and struvite, enabling nucleation even under undersaturated bulk water conditions. These innovative mineral-hydrogel composites offer sustainable nutrient cycling by concurrently removing NH4+ and phosphate from waste to maintain safer nutrient concentrations in aquatic systems. Furthermore, they provide exciting opportunities to upcycle the high-purity heterogeneously formed struvite and CaP as valuable resources for plant and algae growth.

Speaker:  Dr. Young-Shin Jun, Professor, Environmental & Chemical Engineering at Washington University