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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The stability of metal-humate complexes is an important factor determining and predicting speciation, mobility and bioavailability of heavy metals in the environment. A comparative investigation of the complexation of Cu(II) and Pb(II) with humic acid and humic-like ligands, such as benzoic and salicylic acid, was performed. The analysis was realized at pH 4.0, a temperature of 25 °C and at an ionic strength of 0.01 mol dm -3 (NaCl) using the Schubert ion-exchange method and its modified form. The stability constants were calculated from the experimental data by the Schubert method for complexes with benzoic and humic acid. A modified Schubert method was used for the determination of the stability constants of the complexes with salicylic acid. It was found that Cu(II) and Pb(II) form mononuclear complexes with benzoic and humic acid while with salicylic acid both metals form polynuclear complexes. The results indicate that Pb(II) has a higher binding ability than Cu(II) to all the investigated ligands. The Cu(II)-salicylate and Pb(II)-salicylate complexes showed noticeable higher stability constants compared with their complexes with humic acid, while the stabilities of the complexes with benzoic acid differed less. Salicylic and benzoic acids as humic-like ligands can be used for setting the range of stability constants of humic complexes with Cu(II) and Pb(II).

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