Adsorption of Hexavalent Chromium Using Banana Pseudostem Biochar and Its Mechanism

Abstract

A low-cost biochar was prepared through slow pyrolysis of banana pseudostem biowaste at different temperatures, and characterized by surface area and porosity analysis, scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). It was shown that the biochar prepared at low pyrolysis temperature was rich in oxygen-containing groups on the surface. Adsorption experiments revealed that the biochar prepared at 300 °C (BB300) was the best adsorbent for Cr(VI) with 125.44 mg/g maximum adsorption capacity at pH 2 and 25 °C. All the adsorption processes were well described by pseudo-second-order and Langmuir models, indicating a monolayer chemiadsorption. Furthermore, it was demonstrated that adsorption of Cr(VI) was mainly attributed to reduction of Cr(VI) to Cr(III) followed by ion exchange and complexation with the biochar.

Enhancing the adsorption capability of areca leaf biochar for methylene blue by K2FeO4-catalyzed oxidative pyrolysis at low temperature

“…29 The pristine biochar was mainly consisted of OH, COOH, C]O, C]C, C-O and aliphatic C-H groups as prepared at low temperature (&400 C). As previous reports, 30,31 the C]O peaks decreased and aromatic structure formed while higher temperature was applied. Interestingly, the pristine biochar prepared at 500 and 600 C was still rich of C-O groups as C-O peaks (1101 cm À1 ) became stronger.…”

“…This was opposed to other reports. [31][32][33] Comparing to the corresponding pristine biochar, the modied biochar was much richer in aliphatic C-O and COOH groups as pyrolyzed at 200 C. The aliphatic C-O groups of modied biochar decreased but no aromatic rings formed while increasing pyrolysis temperature. Moreover, strong peaks of C]O around 1634 cm À1 were always observed for the modied biochar.…”

Efficient Removal of Cr(VI) from Water by Biochar and Activated Carbon Prepared through Hydrothermal Carbonization and Pyrolysis: Adsorption-Coupled Reduction Mechanism

“…Clearly, biochar and activated carbon are carbon-enriched materials that are approximately 86% to 91% carbon. In addition, three prepared samples had a high content of oxygen, suggesting that they might exhibit a high content of oxygen-containing functional groups on their surface [12,13,15,32]. The Table 1 summaries some corresponding textural properties of three prepared samples.…”

“…In water treatment, activated carbon (AC) and biochar have been acknowledged as promising adsorbents to remove both Cr(VI) anions and Cr(III) cations from the water media and widely applied in many potable water purification and sewage treatment plants. This is presumably because they exhibit an excellent level of porosity (i.e., larger surface area and high total volume), a high concentration of oxygen-containing functional groups (i.e., carboxylic and phenolic), and high mechanical strength [12][13][14][15][16][17]. According to an industrial research report [18], the global demand for AC is expected to increase by 4.2% per year and be up to 2.2 million metric tons by 2022, and the global AC market size is estimated at approximately USD 4.75 billion in 2022.…”

Comparative Study of Cationic Dye Adsorption Using Industrial Latex Sludge with Sulfonate and Pyrolysis Treatment

“…The initial rapid increase of removal efficiency could be ascribed to more adsorption sites by increased adsorbent dosage. The following slight increase might be caused by the aggregation of adsorbent particles or the overlapping of adsorption sites, resulting in the effective surface area of the adsorption decreasing, thereby slightly increasing the amount of adsorption [17,30]. An insufficient or excessive adsorbent dosage would result in low removal efficiency or high cost, therefore 0.2 g/L SLS and 0.6 g/L LSC were selected as optimum adsorbents dosage for the next experiments.…”