Adsorption and removal of the harmful pesticide 2,4-dichlorophenylacetic acid from an aqueous environment via coffee waste biochar: Synthesis, characterization, adsorption study and optimization via Box-Behnken design

Abstract

This study looked at the effectiveness of a biochar made from coffee waste (CWB) in removing the harmful pesticide 2,4-dichlorophenylacetic (2,4-D) from water. The trials' conclusive findings showed that CWB is an effective adsorbent for removing 2,4-D from aqueous solutions. A variety of methods, including Scanning electron microscope (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis, were used to study the CWB. The surface area and pore volume of CWB are comparatively large (422.4 m2/g), and (0.46 cm3/g), respectively. Interestingly, our results show that adsorption behaviour is significantly impacted by changes in solution pH. At pH 6, dosage 0.02 g, the best conditions for high adsorption capacity were discovered. Since adsorption is an endothermic process, its capacity increases as temperature does. The adsorption process was fitted to Langmuir Isothermally and pseudo-second-order model kinetically. It was discovered that a chemisorption mechanism was at work during the entire process. Box-Behnken design (BBD) with Response Surface Methodology (RSM) was used to optimize the parameters such as solution pH, absorbent dosage, temperature and time. Following the instructions, we were able to extract the values of (ΔH°), (ΔS°), and (ΔG°) for 2,4-D, which shown that when utilizing CWB as an adsorbent, the reaction was endothermic and spontaneous. The synthesized CWB adsorbent exhibits outstanding reusability and can be used in adsorption-desorption operations up to five times. It was proposed that the interaction between CWB and 2,4-D may take place through a variety of mechanisms after additional research was conducted to better understand the relationship, including pore filling, π-π interaction, H-bonding, or electrostatic interaction. Our research is the first to demonstrate the efficacy of using CWB as an adsorbent to remove 2,4-D from wastewater samples. The conclusions show that a pH value of 6 is necessary to produce 2,4-D's greatest adsorption capacity onto CWB, which is 276.3 mg/g.