Polyurethane film prepared from ball-milled algal polyol particle and activated carbon filler for NH₃-N removal

This research offers a novel approach of free chemical preparation to obtain algae-based biopolyol through a ball milling method. The algae-based polyurethane (AlgPU) film was obtained from a casting solution made of ball-milled algal polyol particle and methylene diphenyl diisocyanate (MDI). The characteristics of the material had been investigated using Fourier Transform Infrared, Scanning Electron Microscopy - Electron Dispersive Spectroscopy, Differential Scanning Calorimetry, and Tensile Strength Analysis. The surface area was determined by Brunauer-Emmett-Teller (BET) isotherm, meanwhile the total pore volume was by Barrett-Joyner-Halenda (BJH) isotherm, based on the adsorption-desorption of N₂. The addition of activated carbon contributed in the increase of functional group and surface area, which were important for the NH₃-N removal. As a result, the adsorption capacity increased greatly after the addition of activated carbon (from 187.84 to 393.43 μg/g). The results also suggested AlgPU as a good matrix for immobilizing activated carbon filler. The adsorption shows a better fit with Langmuir isotherm model, with R² = 0.97487 and root-mean-square error (RMSE) = 33.91952, compared to Freundlich isotherm model (R² = 0.96477 and RMSE = 44.05388). This means the NH₃-N adsorption followed the assumption of homogenous and monolayer adsorption, in which the maximum adsorption was found to be 797.95 μg/g. This research suggests the potential of newly developed material for NH₃-N removal.