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Lagenaria vulgaris (LV) shell was used as a biosorbent for the removal of heavy metal ions, Pb 2+ , Cd 2+ and Zn 2+ , from aqueous solutions. Experiments were carried out under batch conditions. The effects of contact time, initial pH, temperature and stirring speed on removal efficiency are presented. Sorption of the investigated metals was fast, reaching equilibrium after about 5 to 10 min, depending on the metal. Biosorption was highly pH-dependent, and the optimal pH for investigated metals was in the range of 4.5 to 6.0. The effects of temperature demonstrated that biosorption of the metals is a chemical process. SEM analysis revealed interesting morphological changes after acid refinement of the raw biosorbent and metal uptake that is related to the chemical nature of the biosorption process. EDX analysis of Lagenaria vulgaris biosorbent (LVB) before and after metal sorption revealed that the ion exchange mechanism was the principal sorption process. Fourier transform infrared spectroscopy (FTIR) analysis has shown that major functional groups (carboxyl and hydroxyl) on the biosorbent surface took part in the metal ion uptake process as active sites. The results obtained showed that Lagenaria vulgaris based biosorbent could be used as an effective and low-cost pre-treatment step for removal of toxic metals from wastewaters.

The photochemical decolorization of C.I. Reactive Orange 16 (RO16), a reactive textile azo dye by the UV/H2O2 process using a batch photoreactor with UV lamps emitting at 253.7 nm, was studied. Complete decolorization of 50.0 mg dm-3 initial dye concentration was achieved in less than 6 min under optimal conditions (25 mM initial peroxide concentration, at pH 7.0 and with UV light intensity 1950 μW cm-2). The effect of experimental variables, such as initial pH, initial concentration of H2O2, initial dye concentration, and the intensity of UV light was studied. The highest decolorization rates were performed at peroxide concentration in range from 20 mM up to 40 mM, above which decolorization was inhibited by a scavenging effect of peroxide. The decolorization was more efficient in neutral pHs. The efficiency of the process was improved in lower initial dye concentration and at higher intensity of UV light

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This paper deals with Cr(VI) ion removal from water, by micro-alloyed aluminium composite (MAlC), under flow conditions. In a water environment the MAlC acts as a strong reducing agent. Dissolving it in water is accompanied by the generation of Al(III) ions and reduction of water to H 2 , with OHions. The final product is insoluble Al(OH) 3. A series of Cr(VI) model solutions, with initial pH ranging between 1 and 5, were treated in the original semi-flow system (SFS), which simulated flow conditions well. The results demonstrate a high MAlC efficacy, considering that at the end of the treatment, concentrations of Cr(VI) were below the maximal allowed concentrations for drinking water, in all model solutions. The MAlC mechanism of action is based mainly on processes of reduction and co-precipitation by Al(OH) 3 , because Cr(VI) is removed from the water phase as metal chromium and insoluble Cr(OH) 3. Behaviour of the composite in water is under significant influence of pH, which affects its efficacy and mechanism of action. Therefore, the rate of Cr(VI) removal is greater at the beginning, decreasing towards the end of the treatment. Additionally, the ratio of [metal chromium]/[Cr(OH) 3 ] in precipitate, at the end of the treatment, decreases with increasing initial pH of the model solution. Application of the SFS significantly enlarges efficacy of the MAlC, compared to work under stationary conditions.