Removal of 3-Chloroaniline from aqueous solution by Treated Coffee Waste: Isotherm Modelling and Thermodynamic Studies

Abstract

Background: Chloroaniline is a crucial organic additive commonly applied in medicine, chemical industries, plastics and pesticides. Besides, it is also a widespread pollutant, which has a high degree of persistence, toxicity, accumulation and it is hard to be naturally degraded. Result: 3-chloroaniline (3CA) concentrations were measured in aqueous solution by UV/Vis spectrophotometer. Validation of the calibration curve's linearity, instrumental precision (RSD%), limits of detection and quantification were accomplished. The coefficient of calibration curve (1.0–10.0 mgL-1 3CA) had a high correlation (R² = 0.9997) and the instrumental precision was in the range (RSD% = 0.50–0.74%, n=10). The LOD and LOQ from the regression analysis were 0.20 mgL-1 and 0.61 mgL-1, respectively. A treated coffee waste adsorbent was utilized for 3-chloroaniline removal by process of sorption from aqueous solution. The major components of the coffee waste are the hemicellulose, cellulose, and lignin. The temperature effect (25°C, 35°C and 45°C) on sorption was evaluated, with sorption decreasing by increasing of temperature. Isotherms type L were found and associated with monolayer sorption. The parameters of sorption were examined by employing Langmuir, Freundlich and Dubinin-Radushkevich sorption models. The isotherm models of Langmuir and Dubinin-Radushkevich had acceptable correlation coefficients (R2). The Langmuir and Dubinin-Radushkevich sorption capacities of 3-chloroaniline were found to be 44 to 50 mgg−1. The values of separation factor (RL) were ranging from (0-1) which indicated a favourable sorption. In thermodynamic study the physical sorption process was confirmed by van’t Hoff equation. In addition, the free energy ∆G° and enthalpy ∆H° had negative values which suggested that the sorption was spontaneous, and the process was exothermic. Conclusion: Since the adsorbent used in this study is abundant and available, it is considered a potential adsorbent material for 3CA removal from aqueous fluids and suitable for the wastewater treatment.