End-of-pipe treatment of secondary treated coke-oven wastewater for removal of fluoride, cyanide, phenol, ammoniacal-N and nitrate using waste material: Experiment, modelling and optimization

Abstract

The present investigation focused on End-of-pipe treatment of secondary treated coke-oven wastewater to remove cyanide, phenol, ammoniacal-N, nitrate and fluoride using earthen tea pot (ETP), a local market waste. The effect of parameters like adsorption time (0–10 h), particle size (1–3 mm) and adsorbent dose (10–30 gL−1) was tested for removal of pollutants from synthetic BOD treated coke-oven wastewater (SBTCW) and maximum removal was obtained as cyanide (95.46 ± 0.004%), phenol (99.70 ± 0.005%), ammoniacal-N (47.88 ± 6.31%), nitrate (61.03 ± 2.12%), and fluoride (92.35 ± 0.09%) at adsorption time 10 h, particle size 1 mm and adsorbent dose 10 gL−1. Kinetic study showed that the fluoride removal data fit satisfactorily to the Pseudo 2nd order kinetic model, whereas the Pseudo 1st order model was found to be fitted well to the kinetic data of all other pollutants. Adsorption isotherm study portrayed that the Freundlich isotherm model holds good to represent equilibrium data for the removal of pollutants. Response Surface Methodology (RSM) was used to optimize the removal efficiencies of all five pollutants. The optimum removal condition as shown by RSM study was contact time: 7.3 h, and initial concentrations (ICs) of cyanide, phenol, ammoniacal-N, nitrate and fluoride are 0.71, 10, 400, 100 and 10.1 mgL−1, respectively, and the removal of five pollutants (cyanide, phenol, ammoniacal-N, nitrate and fluoride) were predicted as 40.58%, 90.00%, 41.63%, 96.00% and 45.29%, respectively. Artificial Neural Network model was developed based on experimental points which indicated that the model can calculate abatement of five different pollutants for various operating conditions with reasonably high accuracy. Genetic Algorithm was then used to optimize the removal process of the five pollutants. Regeneration study was conducted to assess the efficacy of the regenerated adsorbent in next cycle of the End-of-pipe treatment of SBTCW. Finally, real secondary treated coke-oven wastewater was collected and treated with the present adsorbent.