Statistical optimization of glyphosate adsorption by biochar and activated carbon with response surface methodology

Abstract

The introduction of glyphosate, found in herbicides, to waterbodies is of concern due to its toxicity and hence potential threat to public health and ecological systems. The present study has compared glyphosate removal from aqueous solution with activated carbon and biochar. Box-Behnken design, and percent contribution with Pareto analysis techniques were used in surface response and efficiency calculations modelled the process conditions and their effects. The adsorption data better fitted the Freundlich isotherm model than the Langmuir model. The rate of glyphosate adsorption was found to follow a pseudo-second-order model. pH of the solutions was regulated by buffering during the adsorption process. Higher efficacy of glyphosate removal was obtained by optimising parameters such as operating pH, initial glyphosate concentration, temperature, adsorbent dose, and contact time. The conditions yielding the best removals were pH 8.0, 0.2 mg/L, 50.0 °C, 11.4 g/L, 1.7 h for activated carbon and pH 5.0, 0.7 mg/L, 50.0 °C, 12.3 g/L, 1.9 h for biochar, for the aforementioned parameters respectively. The maximum removal capacity and efficiency were 0.0173 mg/g and 98.45% for activated carbon, and 0.0569 mg/g and 100.00% for biochar. The test results indicated biochar could be important from the perspective of performance and affordability.