Engineering antifouling UiO-66-NH₂ mixed matrix membranes for geothermal brine pretreatment: Fouling prediction, techno-economic analysis, and environmental assessment

Abstract

This study develops polysulfone/UiO-66-NH₂ mixed-matrix membranes (MMMs) for silica removal from geothermal brine and evaluates their antifouling behavior, fouling mechanisms, techno-economic feasibility, and environmental implications. Incorporation of UiO-66-NH₂ improved membrane hydrophilicity, decreasing the water contact angle from 80.8° to 47.6°, and increased permeability from 158.94 to 376.03 L m −2 h −1 bar −1 . FTIR and XRD confirmed successful UiO-66-NH₂ incorporation, while SEM revealed a well-developed porous structure. The optimized MMM achieved a maximum FRR of 82.94%, showing that backwashing restored flux by reopening pores narrowed by reversible intrapore silica deposition. Hermia-derived modeling confirmed that silica fouling was dominated by internal pore narrowing, rather than surface cake formation. Techno-economic analysis showed that mixed matrix membrane ultrafiltration reduced pretreatment costs to 0.91 and 0.47 USD/m 3 at 100 and 1000 m 3 /day, respectively, compared with 1.29 and 0.68 USD/m 3 for conventional coagulation–flocculation–clarification, but remained less cost-efficient than commercial ultrafiltration at 0.80 and 0.43 USD/m 3 . Both membrane-based routes reduced energy demand and greenhouse gas emissions by approximately 53–54% relative to conventional treatment, although the mixed-matrix membrane system showed slightly greater impacts than commercial ultrafiltration and increased water consumption by approximately 47–48%. These results reveal a clear trade-off between improved antifouling performance and modest economic, energy, emission, and water-use penalties relative to commercial ultrafiltration.