Removal of malachite green from water: Comparison of adsorption in a residue-derived AC versus photocatalytic oxidation with TiO2 and study of the adsorption-photocatalysis synergy.

The literature rarely compiles studies devoted to the removal of pollutants in aqueous media comparing adsorption and photocatalytic degradation, and does not pay enough attention to the analysis of combined adsorption-photocatalytic oxidation processes. In the present manuscript, the removal of malachite green (MG) from aqueous solutions has been investigated in three different sustainable scenarios: i) adsorption on activated carbon (AC) derived from a residue, luffa cylindrica, ii) photocatalytic oxidation under simulated solar light using titanium dioxide (TP) and iii) combined adsorption-photocatalytic oxidation using TP-AC (70/30 wt./wt.) under simulated solar light. The study has revealed that in the three scenarios and studied conditions, the total removal of this endocrine-disrupting dye from the solution takes place in the assayed time, 2 h, in some cases just in a few minutes. MG adsorption in the AC is a very fast and efficient removal method. MG photocatalytic oxidation with TP also occurs efficiently, although the oxidized MG is not totally mineralized. MG removal using the TP-AC composite under simulated solar light occurs only slightly faster to the MG adsorption in the AC, being adsorption the dominating MG removal mechanism for TP-AC. Thus, more than 90% of the removed MG with TP-AC under simulated solar light is adsorbed in this carbon-containing composite. The obtained results highlight the interest in adsorption, being the selection of the most suitable removal method dependent on several factors (i.e., the cost of the AC regeneration, for adsorption, or the toxicity of the intermediate oxidation species, for photooxidation). Paying attention to MG photooxidation with TiO2, comparison of two working photodegradation schemes shows that the direct photodegradation of MG from solution, avoiding any initial dark equilibrium period, is more efficient from a time perspective. The use of scavengers has proved that MG photodegradation occurs via an oxidation mechanism dominated by superoxide anion radicals.

[Management of presbyopic hyperopes by centered presbyLASIK]. / Prise en charge de patients hypermétropes presbytes par chirurgie cornéenne de type presbylasik centré.

PURPOSE: To evaluate efficacy and patient satisfaction of presbyopic hyperopes treated with centered PresbyLASIK (multifocality centered on near vision) by the SUPRACOR technique (Technolas Perfect Vision). MATERIALS AND METHODS: This is a retrospective study carried out at Percy Army Teaching Hospital from September 2011 through September 2013. Fifty-nine eyes of 29 patients were included and underwent PresbyLASIK. Study parameters included uncorrected binocular distance (DVA) and near (NVA) visual acuity, aberrometry, central corneal curvature by corneal topography (bump), and patient satisfaction (questionnaire). RESULTS: Mean uncorrected binocular visual acuity was found to be 0.09 logmar for DVA and 0.22 for NVA on post-operative day one, 0.04 logmar for DVA and 0.17 for NVA at 1 month post-operatively, 0.15 logmar for DVA and 0.19 for NVA at 3 months post-operatively, and -0.02 logmar for DVA and 0.18 for NVA at 6 months post-operatively. Mean central corneal curvature was found to be 2.56±0.9 diopters. There were significantly more higher-order aberrations in the central 5mm post-operatively (P<0.01). Among the patients undergoing bilateral SUPRACOR LASIK, 79% were entirely satisfied with the surgery, and all patients would recommend the procedure to their family and friends. Eighty-six percent of these patients acheived total spectacle independence at distance and near. CONCLUSION: SUPRACOR PresbyLASIK is a method of choice in overcoming spectacle dependence in presbyopic hyperopes.

Contribution to the study of electrocoagulation mechanism in basic textile effluent.

Electrocoagulation method with iron electrode is used to treat the industrial textile wastewater in batch reactor. The effects of operating parameters such as time and potential electrolysis on the decolourization and COD removal efficiency have been investigated. The results indicate that electrocoagulation is very efficient and able to achieve 100% colour and 84% COD removal in 3 min at potential 600 mV. The effluent wastewater is very clear and its quality exceed the direct discharge standard. Furthermore, the mechanism of electrocoagulation is elucidated by zeta potential measurement.

Removal of trivalent chromium from tannery waste waters using bone charcoal.

The ability of bone charcoal to remove Cr(III) from aqueous solutions by adsorption has been investigated. The adsorbent used was first characterised and then the adsorption was studied as a function of time and amount of charcoal. Tests were carried out with synthetic solutions whose Cr concentrations (500 mg L(-1)) were similar to those found in some effluents of Moroccan tannery industries. Cr removal efficiencies higher than 90% were obtained at pH 3.5 using 3 g of bone charcoal and a stirring time of about 30 min. Results of Cr removal by all sieved fractions of bone charcoal had shown the same interesting capabilities for Cr(III) retention. The cross interference with other elements was also investigated. Pre-treatment of bone charcoal by nitric acid led to an increase in its specific surface area but induced a drastic reduction in its Cr elimination abilities. Adsorption tests were also carried out using calcinated bone charcoal. The results obtained showed a similar percentage of Cr retention to those found with untreated bone charcoal. On the other hand, a double treatment of bone charcoal with HCl and NaOH provided an enhancement of Cr(III) retention. The role played by the mineral fraction of the solid phase of bone was thus evidenced.