Iron oxide loaded biochar/attapulgite composites derived camellia oleifera shells as a novel bio-adsorbent for highly efficient removal of Cr(VI)

Agricultural processing by-product have been used as the feed stock for effluent treatment to promote the utilization of agricultural waste, the development of green sustainable and construct a green ecological circle nowadays. Based on camellia oleifera shells, attapulgite, and ferric chloride, a novel iron oxide loaded biochar/attapulgite composite (Fe-BC/A) was synthesized via a one-step pyrolysis process and as a low-priced and efficient adsorbent for Cr(VI) removal from aqueous solution. The structure and composition of Fe-BC/A were characterized by SEM-EDS, FT-IR, XRD, and XPS, which confirmed iron oxide (analogous to alpha-Fe2O3 and beta-FeOOH) and attapulgite clay were successfully incorporated with biochar. The maximum adsorption capacity of Cr(VI) by Fe-BC/A was 107 mg/g at pH 2.0, which was much higher than the original biochars (BC: 54.38 mg/g) and biochar/attapulgite composites (BC/A: 81.75 mg/g). The adsorption behavior of Fe-BC/A fitted better with pseudo second-order model and Freundlich model, which indicated that multilayer chemisorption might dominate Cr(VI) adsorption. The thermodynamic analysis of Fe-BC/A represented that removal of Cr(VI) was a spontaneous and endothermic process. Batch experiments results demonstrated that Fe-BC/A had great adsorption capability of Cr(VI) in a broad pH extent of 2.0-10.0, whose most favorable elimination for Cr(VI) at pH of 2.0 and the removal efficiency of Cr(VI) was about 80% at pH = 10 (C-0 = 100 mg/L, 30 degrees C). Fe-BC/A exhibited a prominent tolerance to the coexisting ions during Cr(VI) removal and only a slight decrease (8.27%) in elimination efficiency after five adsorption-desorption cycles. Mechanism study revealed that electrostatic attraction, reduction, anion exchange, and complexation were involved in the removal of Cr(VI). This study implied the potential practical application of Fe-BC/A in the future Cr(VI) remediation from wastewater.

Automated summary

Fe-BC/A, a novel iron oxide loaded biochar/attapulgite composite synthesized from camellia oleifera shells, attapulgite, and ferric chloride, exhibits high adsorption capacity for Cr(VI) and excellent tolerance to coexisting ions. The adsorption behavior fits well with the pseudo second-order model and Freundlich model, showing great adsorption efficiency under various conditions.