Production of modified sunflowers seed shells for the removal of bisphenol A.

In this present study, an abundant, available lignocellulosic biomass, sunflower seed shells, SSS, was used as a precursor to prepare an effective eco-adsorbent by treatment with H2SO4. A study of the surface characteristics of raw and acid-treated SSS (ACS) has shown that the addition of H2SO4 greatly affected the physicochemical properties of the obtained eco-adsorbent, improving the BET surface area from 6.106 to 27.145 m2 g-1 and surface oxygen-rich functional groups. Batch experiments were performed to assess the removal efficiency of a phenolic compound, bisphenol A (BPA), on the adsorbents. Several parameters were evaluated and are discussed (contact time, pollutant concentration, adsorbent dosage, and pH), determining that the adsorption efficiency of BPA onto SSS was notably improved, from 20.56% to 87.81% when a sulfuric acid solution was used. Different canonical and stochastic isotherm models were evaluated to predict the experimental behaviour. A dynamic study was performed based on the models of reaction kinetics and those of mass transfer. The results showed that the adsorption kinetics of BPA obey the fractal like-kinetic model of Hill for all experimental conditions. The equilibrium data are well suited to the Hill-Sips isotherm model with a determination coefficient >0.999. The kinetic modelling also indicates that the adsorption processes of BPA onto ACS are exothermic and proceed through a physical mechanism. A mass transfer study, using simplified models, proved that the process is controlled by intraparticle and film resistances to mass transfer of the BPA.

Simultaneous biotreatment of Polycyclic Aromatic Hydrocarbons and dyes in a one-step bioreaction by an acclimated Pseudomonas strain.

A Pseudomonas stutzeri strain acclimated to the presence of neoteric contaminants has been proposed for simultaneously remediating an effluent polluted with Polycyclic Aromatic Hydrocarbons and a diazo dye. The pollutants chemical nature imposed a strict control of both the medium composition and the operating conditions. pH, temperature and agitation rates of 7.0, 37.5 and 146 rpm, respectively, led to optimum levels of contaminant removal (higher than 60%) after RSM optimization. The validity of these conditions was checked at flask and bioreactor scale and the kinetics of the biotreatment was elucidated. The simulation of this one-step process applied at larger scale for the remediation of a 200,000 m(3)/year-effluent from a leather factory was compared with a conventional two-steps option. Great reductions in treatment times and in investment and manufacturing costs were concluded, proving the promising potential of the proposed process.

Influence of redox mediators and metal ions on synthetic acid dye decolourization by crude laccase from Trametes hirsuta.

In this paper, the effect of redox mediators on synthetic acid dye decolourization (Sella Solid Red and Luganil Green) by laccase from Trametes hirsuta cultures has been investigated. All the redox mediators tested, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1-hydroxybenzotriazole (HBT) and Remazol Brilliant Blue R (RBBR), led to higher activities than those obtained without mediators addition showing the suitability of the laccase/mediator system (LMS) in the decolourization of acid dyes. HBT was by far the most effective mediator, showing a decolourization percentage of 88% in 10 min for Sella Solid Red and of 49% in 20 min for Luganil Green. On the other hand, the stability of laccase against several metal ions, normally found in textile wastewater, was assessed. Laccase was stable at a concentration of 1mM for 7d against all the metal ions tested except for Zn+2, CrO4(-2), Cd+2, Cr2O7(-2), Fe+2, Cu+2 and especially Hg+2. When the concentration was increased to 10mM laccase stability decreased against all the metals assayed, in particular against Fe+2. In addition, the effect of metal ions on the decolourization process was also studied. It was found that Hg+2 inhibited the dye decolourization process, being the presence of HBT absolutely required for dye decolourization.

Different proportions of laccase isoenzymes produced by submerged cultures of Trametes versicolor grown on lignocellulosic wastes.

The white-rot fungus Trametes versicolor grown in submerged culture produced two laccase isoenzymes, LacI and LacII. Addition of insoluble lignocellulosic materials into the culture medium increased the total laccase activity. The proportion of laccase isoenzymes also changed depending on the lignocellulosic material employed, with ratios of activity LacII/LacI from 0.9 (barley straw) to 4.4 (grape stalks). Besides, this proportion played an important role in the dye decolourisation.