Facile preparation of micro-porous biochar from Bangladeshi sprouted agricultural waste (corncob) via in-house built heating chamber for cationic dye removal

Herein, in-house built heating chamber aided facile preparation of biochar was carried out using Bangladeshi sprouted corncob as the precursor for removing methylene blue (MB). The corncob biomass (CCB) was pyrolyzed at 700 °C for 2hrs (heating rate: 10 °C/min) using the in-house built heating chamber in a muffle furnace, eliminating the necessity of pyrolytic chamber. The prepared corncob biochar (CCBC) was characterized for elemental composition, crystallinity (XRD), functional groups (ATR-FTIR), surface morphology-elemental composition (SEM-EDX), surface area (BET), surface charge (point of zero charge), particle size-stability (DLS-zeta potential) and thermal stability (STA). Adsorption efficacy of CCBC was investigated in batch experiment with MB dye as well as effect of various factors such as contact time (5–120 min), initial MB concentration (7–15 mg/L), pH (2–10) and adsorbent dosage (10–35 mg). Without any chemical treatment for activation, CCBC produced maximum adsorption capacity (Qmax) of 20.42mgg−1 at 25 °C. The adsorption behavior of MB by CCBC could be better understood by Langmuir isotherm and Pseudo-second order kinetic model as they were the best fitted isotherm and kinetic models. Thus, waste to treat waste, meaning agricultural wastes like corncob can easily be converted into effective adsorbent for treating dye bearing wastewater

Environmental remediation by hydroxyapatite: Solid state synthesis utilizing waste chicken eggshell and adsorption experiment with Congo red dye

This study reports the adsorption efficacy of hydroxyapatite (HAp) for removing Congo Red (CR) dye from aqueous solution. HAp was synthesized utilizing chicken eggshell as a precursor of Ca source. Solid state synthesis method was implemented which comprised calcination at 950 °C (E-HAp950). XRD analysis confirmed the formation of bi-phasic HAp with 15.5% of β-TCP. Elemental composition was evaluated by XPS and EDX analysis. FESEM analysis revealed the particles are of plate and spherical shaped also confirmed by the TEM images. DLS particle size, zeta potential, BET surface area and point of zero charge were also evaluated. Adsorption efficacy of E-HAp950 for removing CR was evaluated by batch adsorption experiment. Maximum adsorption capacity (qmax) was found to be 9.64 mgg−1 which was best explained by the non-linear fitting (R2 = 0.98) of Langmuir isotherm. Adsorption kinetics profusely followed pseudo second order kinetic model (R2 = 0.999) with qe (experimental) being very much closer to qe (calculative) for this model. Thus, hydroxyapatite prepared by utilizing eggshell waste through solid state method has the potential to remove toxic dyes