A Pongamia pinnata pods based activated carbon as an efficient scavenger for adsorption of toxic Co(II): kinetic and thermodynamic study

One-step in-situ sustainable synthesis of magnetic carbon nanocomposite from corn comb (MCCC): agricultural biomass valorisation for pollutant abatement in wastewater

This study explored a novel, eco-friendly, sustainable, low-cost, and abundantly available corn comb (CC) agricultural biomass waste-derived one-step in-situ synthesis of magnetic carbon (MCCC) as an efficient adsorbent for water decontamination applications. Herein, we developed a robust and easily separable MCCC by carbonization of Fe(NO₃)₃.9H₂O single iron salt-soaked CC at 500 °C for 5 h. The as-synthesized MCCC was confirmed for their physicochemical properties by various characterization techniques viz. scanning electron microscopy (SEM), high-resolution transmission emission microscopy (HR-TEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface area measurements by Brunauer-Emmett-Teller (BET) study, Raman analysis, and magnetic behavior by VSM analysis. The adsorption properties of MCCC on prototypical pollutant methylene blue (MB) was monitored depending on the effect of pH, adsorbent dose, contact time, and varying concentrations of MB. Especially, the π-π interactions played important role in the adsorption of MB at acidic pH (pH = 4). The MCCC displayed a maximum uptake capacity of 120.73 ± 0.63 mg/g toward MB. The Langmuir, Freundlich, and Temkin adsorption isotherm models were fitted with determined coefficient (R²) values of 0.99, 0.95, and 0.96 respectively. The kinetics of the adsorption process was well fitted with a pseudo-second-order model (R² = 0.99). Most significantly, the as-designed easily separable, and reusable adsorbent, MCCC was effectively applied for the abatement of pollutants, different kinds of dyes, pesticides, and industrial wastewater samples. The sustainable, affordable, and waste to wealth-based MCCC with a simple synthesis methodology can be fruitfully applicable for environmental remediation and water decontamination.

Adsorption of Co(II) from aqueous solution using municipal sludge biochar modified by HNO3

Here adsorption studies were proposed on a carboxylated sludge biochar (CSB) material modified by HNO₃ to assess its capacity in the removal of cobalt from aqueous solution. The as-prepared sludge biochar material was characterized by Brunauer-Emmett-Teller (BET) analysis, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The isotherm process could be well described by the Langmuir isotherm model. The adsorption kinetics indicated that cobalt adsorption followed a pseudo-second-order kinetics model. The mechanism between Co(II) and biochar involved electrostatic interaction, ion exchange, surface complexation and physical function. The adsorption capacity on CSB was as high as 72.27 mg·g^-1, surpassing original sludge biochar (SB) as CSB had abundant oxygen-containing functional groups and many hydroxyls, plus the BET surface areas increased when SB was modified by HNO₃, which stimulated adsorption effect. Therefore, this work shows that CSB could be used as an efficient adsorbent to remove Co(II) in wastewater.