2,4-Dichlorophenoxyacetic acid adsorption on adsorbent prepared from groundnut shell: Effect of preparation conditions on equilibrium adsorption capacity

Abstract

This work highlights the preparation of adsorbents using a common agricultural waste [groundnut shell (GS)] and their characterization and adsorption efficacy. The study investigates the chemical, physical, mineralogical, and morphological characteristics of three types of adsorbents produced using groundnut shell (GS),according to three distinct methods[ash by combustion (GSA), biochar by pyrolysis (GSC),and activated carbon by chemical activation (GSAC)of bio char (KOH : bio char: 2.5:1)]. The synthesized adsorbents (GSA, GSC, and GSAC) were characterized by scanning electron microscopy (SEM), X-ray fluorescence (XRF), CHNS (ultimate analysis), Benner–Emmer–Teller (BET), and Fourier transform infrared (FTIR) techniques. A progressive increase in BET surface area was noted with the change in preparation methods: GSA (8 m2/g), GSC (43 m2/g), and GSAC (709 m2/g). To the best of our knowledge, for the first time ever, adsorbents prepared using GS were characterized in detail and their adsorptive abilities were investigated using a commonly used herbicide, 2, 4-dichlorophenoxyacetic acid (2,4-D),as a representative. Batch experiments were conducted to study the effect of different operational parameters such as adsorbent dose, initial 2,4-D concentration, and contact time. The adsorption capacity of GSA, GSC, and GSAC was found to be 0.87, 3.02, and 250 mg/g, respectively, whereas the equilibrium time was found to be 60, 120, and 240 min, respectively. The adsorption capacity of GSAC (250 mg/g) was found to be comparable with the highest reported values in the literature [langsat empty fruit bunch activated carbon (LEFBAC; 261 mg/g) and pumpkin seed hull (260 mg/g)]. Keywords: Additive, Adsorption, Characterization, Utilization