Thermally Modified Bentonite as an Effective Adsorbent for Caffeine Removal: A Techno-Economic Perspective

Caffeine has been recognized as an emerging pollutant in aquatic ecosystems due to its persistence. This study evaluated the techno-economic viability of caffeine removal using thermally modified bentonite (Na–Bent–400) as an adsorbent. Caffeine removal was simulated under two operational schemes: Scenario 1 (S1: Adsorption–Disposal), where Na–Bent–400 is discarded following saturation, and Scenario 2 (S2: Regeneration–Reuse–Disposal), which integrates adsorbent regeneration to enable the reuse of Na–Bent–400 in a second adsorption before final disposal. Using the optimized model for caffeine removal (95.97% removal efficiency in batch operation: 2.26 g/L Na–Bent–400, 30 mg/L caffeine, and pH 8), the process was scaled up through process simulation in Aspen Plus (V14) for a treatment flow rate of 8 L/s (252,288 m3/year). Capital expenditure (CapEx) was estimated at USD 331,004 without adsorbent regeneration (S1) and USD 486,725 with regeneration (S2), showing a 47% increase due to auxiliary equipment and operational complexity; however, integrating adsorbent regeneration minimizes long-term operational expenditures by reducing raw material requirements and wastewater treatment costs. Estimated water treatment costs based on operational expenditures (OpEx) are USD 1.38/m3 for S1 and USD 0.74/m3 for S2. A sensitivity study found that caffeine concentrations above 30 mg/L have little effect on treatment costs. By evaluating these scenarios, this study demonstrates the preliminary techno-economic viability of thermally modified bentonite for treating caffeine-contaminated agroindustry effluents.