Abstract
Dye effluent has attracted considerable attention from worldwide researchers due to its harm and toxicity in recent years; as a result, the treatment for dye has become one of the focuses in the environmental field. Adsorption has been widely applied in water treatment owing to its various advantages. However, the adsorption behaviors of the new materials, such as the 2D black phosphorus (BP), for pollution were urgently revealed and improved. In this work, BP, black phosphorene (BPR), and sulfonated BPR (BPRS) were prepared by the vapor phase deposition method, liquid-phase exfoliating method, and modification with sulfonation, respectively. The three BP-based materials were characterized and used as adsorbents for the removal of methylene blue (MB) in water. The results showed that the specific surface areas (SSAs) of BP, BPR, and BPRS were only 6.78, 6.92, and 7.72 m2·g−1, respectively. However, the maximum adsorption capacities of BP, BPR, and BPRS for MB could reach up to 84.03, 91.74, and 140.85 mg·g−1, which were higher than other reported materials with large SSAs such as graphene (GP), nanosheet/magnetite, and reduced graphene oxide (rGO). In the process of BP adsorbing MB, wrinkles were generated, and the wrinkles would further induce adsorption. BPR had fewer layers (3–5), more wrinkles, and stronger adsorption capacity (91.74 mg·g−1). The interactions between the BP-based materials and MB might cause the BP-based materials to deform, i.e., to form wrinkles, thereby creating new adsorption sites between layers, and then further inducing adsorption. Although the wrinkles had a certain promotion effect, the adsorption capacity was limited, so the sulfonic acid functional group was introduced to modify BPR to increase its adsorption sites and promote the adsorption effect. These findings could provide a new viewpoint and insight on the adsorption behavior and potential application of the BP-based materials.
Highlights
In recent years, with the rapid development of new textiles, printing and dyeing technologies have become more and more complicated
The results indicated that the adsorption isotherms of the three black phosphorus (BP)-based materials for methylene blue (MB) were fitted better by the Langmuir model
ΔS0 > 0 indicated that entropy increased in the adsorption process, which implied that the entropy changes caused by the desorption of MB on the surface of the three BP-based materials were greater than those caused by the adsorption
Summary
With the rapid development of new textiles, printing and dyeing technologies have become more and more complicated. The widely applied adsorption technology mainly utilizes the porous structures and the active sites in the adsorbents for the removal of pollution [8,9]. It has many advantages, such as high adsorption efficiency, simplicity, and selective enrichment of certain compounds [10]. The maximum theoretical specific surface area (SSA) of BPR was calculated to be 2400 m2·g−1, and BPR had a high adsorption capacity for MB (1232 ± 283 mg·g−1). The adsorption mechanisms were clarified through characterization and compared with other materials, which could provide a reference for the future application of BP-based materials in the environmental field. The adsorption capacities and mechanisms of BP, BPR, and BPRS for MB were investigated and compared
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