Coagulative removal of polystyrene microplastics from aqueous matrices using FeCl3-chitosan system: Experimental and artificial neural network modeling

Effluent from sewage treatment plants (STPs) is a significant source of microplastics (MPs) re-entry into the environment. Coagulation-flocculation-sedimentation (CFS) process as an initial tertiary treatment step requires investigation for coagulative MPs removal from secondary-treated sewage effluents. In this study, experiments were conducted on synthetic water containing 25 mg/L polystyrene (PS) MPs using varying dosages of FeCl3 (1–10 mg/L) and chitosan (0.25–9 mg/L) to assess the effect of process parameters, such as pH (4−8), stirring speed (0–200 rpm), and settling time (10–40 min). Results revealed that ∼89.3% and 21.4% of PS removal were achieved by FeCl3 and chitosan, respectively. Further, their combination resulted in a maximum of 99.8% removal at favorable conditions: FeCl3: 2 mg/L, chitosan: 7 mg/L, pH: 6.3, stirring speed: 100 rpm, and settling time: 30 min, with a statistically significant (p 98% removal at favorable conditions. [Display omitted] •Coagulative polystyrene (PS) microbeads removal by FeCl3 and chitosan studied.•Maximum PS removal of 99.8% was achieved by 2 mg/L of FeCl3 with 7 mg/L of chitosan.•ANN model agreeably predicted coagulative PS removal with RMSE: 1.0643 and R2: 0.9997.•Charge neutralization and adsorption were major coagulation mechanisms for PS removal.•FeCl3-chitosan system showed > 98% PS removal from STP effluents for practical use.