A novel approach for methylene blue removal by calcium dodecyl sulfate enhanced precipitation and microbial flocculant GA1 flocculation

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2016-11, Vol.303, p.1-13
• Main Authors: Yang, Zhaohui, Li, Min, Yu, Mingda, Huang, Jing, Xu, Haiyin, Zhou, Yan, Song, Peipei, Xu, Rui
• Format: Article
• Language: English
• Subjects: Calcium; Calcium dodecyl sulfate; Calcium ions; Calcium sulfate; Flocculating; Methylene blue; Micelles; Microbial flocculant; Microorganisms; Scanning electron microscopy; Sodium dodecyl sulfate; Solubilization; Sulfates
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2016.05.101

[Display omitted] •A novel approach for the efficient removal of MB was proposed.•SDS solubilization and Ca2+ effect were combined to reduce the solubility of MB.•MB precipitated from aqueous solution by adsorbing onto the Ca(DS)2 particles.•The Ca(DS)2 particles adsorbed MB were flocculated by MBFGA1. A novel approach was proposed for the removal of methylene blue (MB), a soluble cationic dye, from aqueous solution by calcium dodecyl sulfate (Ca(DS)2) enhanced precipitation which was based on the solubilization of sodium dodecyl sulfate (SDS) on MB and Ca2+ effect on SDS micelles, and microbial flocculant GA1 (MBFGA1) flocculation. The independent and interactive effects of factors, such as SDS, Ca2+ and MBFGA1 dosages, on the MB removal and interaction between SDS and Ca2+ were investigated. The response surface methodology (RSM), environmental scanning electron microscope (ESEM) and energy dispersive spectrometer (EDS) analysis were employed to discuss the interaction mechanism between SDS and Ca2+, and MB removal mechanism. The results showed that MB and SDS removal efficiency could reach 98.63% and 88.97%, respectively, with pH (10), MB (50mg/L), SDS (8mM), Ca2+ (5mM) and MBFGA1 (4mL/L). Under the optimal conditions, residual SDS and Ca2+ concentrations in the upper phase were 0.88mM and 1.27mM, respectively, which reached the Ksp of Ca(DS)2. The concentration consumption ratio between SDS and Ca2+ was 2.0. The interaction between SDS and Ca2+ was depended on the SDS-Ca2+ concentration ratio in aqueous solution rather than the CMC of SDS. When Ca2+ concentration was relatively sufficient, SDS micelles containing the solubilized MB (SDS-MB micelles) would disassemble to generate MB loaded Ca(DS)2 particles (CDS-MB particles) which would be flocculated by MBFGA1. Whereas, when SDS concentration was superfluous relatively, SDS micelles formed in the upper phase would redissolve the CDS-MB particles in flocs.