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2016):Preparation and characterization of microfiltration apatite membrane over low cost clayalumina support for decolorization of dye solution, Desalination and Water Treatment, A B S T R A C TApatite material obtained from natural sources of Tunisian mineral has been used for the development of membrane over clay-alumina-based microporous supports. For this purpose, supports of single-channel and 19-channel circular configurations were used. The apatite powder used for membrane preparation had average pore diameter of 4.02 μm. Coating formulation has been optimized to obtain stable suspension. Powder loading of 4 wt.% was found as optimum for obtaining a proper microfiltration membrane with 0.2 μm pore diameter. Singlechannel membrane was used for characterization. The application to color removal from synthetic reactive dye solution was performed using membrane with 19-channel configuration. An average water flux of 200 and 80 l/m 2 h was obtained for 19-channel support and membrane, respectively, in laboratory scale setup. Reactive red dye removal from synthetic dyeing solution was achieved up to 99%. Resulting saturated membrane was successfully regenerated using H 2 O 2 at various concentrations and contact time. Color separation efficiency of the membrane (g/m 2 ) has been evaluated as an indicator of membrane regeneration. Moreover, apatite membrane-based separation of reactive red dye has been compared with adsorption using the apatite powder followed by membrane separation. Apatite membrane-based separation was found to be more efficient compared to adsorptive separation using apatite powder.

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This work reports for the first time a straightforward and efficient approach to covalent surface functionalization of a sustainable graphene-like nanomaterial with abundant carboxylic acid groups. This approach results in an efficient and robust chelatant platform for anchoring highly dispersed ultrasmall palladium particles with excellent catalytic activity in the reduction of both cationic (methylene blue, MB) and anionic (eosin-Y, Eo-Y) toxic organic dyes. The large-specific-surface-area (S BET = 266.94 m 2 /g) graphene-like nanomaterial (GHN) was prepared through a green and cost-effective pyrolysis process from saccharose using layered bentonite clay as a template. To introduce a high density of carboxylic acid functions, GHN was first doubly functionalized by successive grafting reaction using two different strategies: (i) in the first case, GHN was first grafted by (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and then bifunctionalized by chemical grafting of tris(4-hydroxyphenyl)methane triglycidyl ether (TGE). In the second case, the grafting order of the two molecules has been reversed. GHN-GPTMS-TGE provided the highest number of grafted reactive epoxy groups, and it was selected for further functionalization with carboxylic acid functions via a ringopening reaction through a two-step hydrolysis (H 2 SO 4 )/oxidation (KMnO 4 ) approach. The GHN nanomaterial bearing carboxylic acid groups was then treated with sodium hydroxide to produce a deprotonated carboxylic acid-rich platform. Finally, due to a high density of accessible chelatant carboxylic acid groups, GHN−COO − binds strongly a great amount of Pd 2+ ions to form stable complexes which after reduction by NaBH 4 leads to highly dispersed, densely anchored, and uniformly distributed nanoscale Pd particles (d ∼ 4.5 nm) on the surface of the functionalized GHN. The GHN−COO − @PdNPs nanohybrid proved to be highly efficient for dye reduction by NaBH 4 in aqueous solution at room temperature. Moreover, because of the high stability of the asprepared graphene-like supported PdNPs, it exhibited very good reusability and could be recycled up to eight times without any significant loss in activity.

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