Valorization of Natural Residue into Activated Carbon:Example of the Shells of the African Baobab Fruit(Adansonia digitata)L.

This study deals with the valorization of natural residues into activated carbon prepared from waste“Baobab fruit shell”from the Fatick Region,Senegal.Thus,after the preparation of the baobab shell,a chemical activation with orthophosphoric acid H3PO4(85%)was performed followed by pyrolysis at 530°C.To eliminate possible carbonization residues,the activated carbons were impregnated in 0.1 M hydrochloric acid and/or soda solutions and then washed thoroughly with distilled water to obtain a pH between 6.5 and 7.The latter were then dried in an oven at 105°C for 24 h.A characterization was carried out to determine the moisture content,the ash content,the iodine and methylene blue indices,the surface functions and the pH at zero charge point(pHpzc).The moisture and ash contents were 1.87%and 0.72%,respectively.The iodine and peroxide indices obtained were 939,09 mg/g and 575.73 mg/g,respectively.Surface function analysis by Boehm’s method showed that the acidic functions were higher than the basic functions and their pHpzc was lower than neutrality.The best efficiency of methylene blue removal was 99.75%and was obtained with a mass of 0.150 g of activated carbon,pH equal to 10,an initial concentration of methylene blue of 200 mg/L and a contact time of 35 min.

Bonding Orthodontic Ceramic Brackets to Ceramic Restorations:Evaluation of Different Surface Conditioning Methods

The purpose of this study was to compare the shear bond strength and Adhesive Remnant Index of four different veneering ceramic materials to ceramic brackets. Additionallly, a further aim of this study was to overcome the etching using hydrofluoric acid which is noxious and could seriously damage the corneas of the eyes. Two surface conditioning methods of four ceramic materials before bonding brackets were examined: in group 1 an air particle abrasion with 25 μm aluminium trioxide (4 seconds at a pressure of 2.5 bars) and subsequently a silane coupling agent (Espe Sil, 3M Unitek, Monrovia, USA) was applicated on one side of each ceramic specimen (10 per group). In group 2 one side of each sample (20 per group) was etched with 37.0 per cent orthophosphoric acid for two minutes and was followed by a silane application (Espe Sil, 3M Unitek, Monrovia, USA). After this procedure the self-ligating ceramic brackets Clarity SL (3M Unitek, Monrovia, USA) brackets were bonded to the ceramic blocks and a thermocycling process started (5°C - 55°C, 6000 cycles). Then, shear bond strength and Adhesive Remnant Index (ARI) were measured. To determine statistical differences Oneway-ANOVA and Tukey Post-hoc test were performed. Hydrofluoric acid seems not to be justifiable anymore for preparing the surface of dental ceramic restorations before bracket bonding. Sandblasting with 25 μm aluminium trioxide and the use of orthophosphoric acid (37.0 per cent) seem to prepare the surface of ceramic restoration sufficiently before ceramic bracket bonding. The found level of shear bond strength values seems to be sufficient for bonding ceramic brackets to ceramic restorations.