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This study, for the first time, rendered crab shell activated biochar modified by potassium hydroxide (KOH) impregnation (CSAB), revealing a new potential application in the removal of diesel oil from oily wastewater. The structural characteristics of crab shell biochar (CSB) and CSAB were investigated by SEM, and the crystal structure and optical properties of as-prepared samples were analyzed using XRD and FTIR. Results showed that CSAB had stratified surface structure morphology, abundant functional groups, and that its high specific surface area could reach up to 2441 m2/g, which was about eight times larger than that of untreated CSB (307 m2/g). An adsorption isotherm study indicated that the actual adsorption process both of CSAB and CSB were found to fit better with the Freundlich equation. Moreover, chemical interaction controlled the adsorption kinetics efficiency while the adsorption equilibrium capacity was 93.9 mg/g. Due to its highly developed pore structure, unique surface characteristics, and effective adsorption performance, this low-cost activated carbon had the potential to serve as an efficient adsorbent for water pollution purification.

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In this study, carbonized kelp biochar (AKB) modified by KOH impregnation and photocatalytic Bi2MoO6/AKB composite (BKBC) nanomaterials were the first time successfully synthesized for efficient removal of dyes in aqueous solution. BET, XRD, FT-IR, and SEM were employed to characterize as-prepared samples. UV-vis and other test results indicated that the removal efficiency of methylene blue (MB) was 61.39% and 94.12% for BKBC and AKB, respectively, which was up to 13 times and 20 times higher in comparison with pure Bi2MoO6 (PBM). In addition, the equilibrium adsorption capacity of MB could reach up to 324.1 mg/g for AKB. This high dyes adsorption performance could be likely attributed to its high specific surface area (507.177 m2/g) and its abundant presence of various functional groups such as –OH and =C–H on AKB. Particularly, the existing of amorphous carbon and transition metal oxides, such as Fe2O3 and Mn5O8, could be beneficial for the photodegradation of MB for AKB. Meanwhile, experimental data indicated that adsorption kinetics complied with the pseudo-second order model well, and all of the tests had satisfactory results in terms of the highly efficient adsorption and photodegradation activity of AKB nanomaterials, which suggested its great potential in wastewater treatment.

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