ABSTRACT:The methylolation of softwood and hardwood lignosulfonates was studied. Six different lignosulfonate samples (three from hardwoods and three from softwoods) were characterized in order to assess their suitability for methylolation. The techniques employed in characterization were UV/vis spectroscopy, Fourier transform infrared (FTIR), and 1 H-nuclear magnetic resonance ( 1 H-NMR). The best properties were shown by softwood ammonium lignosulfonate (LAS), which was used to optimize the operation conditions to promote the Lederer-Manasse reaction. The methylolation variables studied were the sodium hydroxide-to-lignin molar ratio, the formaldehyde-to-lignin molar ratio, time, and temperature. The reaction was followed by the changes in the concentration of free formaldehyde. IR and NMR spectra of nonmodified and modified samples were used to study the structural changes. Under optimum operation conditions, softwood lignosulfonates showed higher reactivity toward formaldehyde than did hardwood lignosulfonates.
A catalyst based on Fe supported on gamma-Al(2)O(3) has been prepared and tested for catalytic wet peroxide oxidation (CWPO) of cosmetic wastewaters. The influence of the main operating conditions (space-time, temperature, and H(2)O(2) dose) have been investigated. Working with this self-made Fe/gamma-Al(2)O(3) catalyst at 85 degrees C, with a space-time of 9.4 kg(cat) h/kg(COD) and a dose of H(2)O(2), corresponding to 0.5 times the theoretical stoichiometric H(2)O(2)/COD ratio, a substantial COD reduction (around 80%) has been reached with a complete consumption of H(2)O(2). The locally allowable limit of COD for industrial wastewaters discharge to the municipal sewer system can be achieved at lower temperature and space-time. The catalyst showed a high stability in 100 h time on stream tests, where COD and TOC reductions around 82 and 60%, respectively, were maintained working at 85 degrees C and 9.4 kg(cat) h/kg(COD) space-time. Fe leaching from the catalyst upon that time on stream was lower than 3% of the initial load.
Bimetallic Pd-Rh catalysts supported on pillared clays have been prepared and tested for aqueous-phase hydrodechlorination (HDC) using 4-chlorophenol (4-CP) as target compound. These bimetallic catalysts combine the higher activity of Rh with the better stability of Pd found in previous works with monometallic catalysts. Different combinations of Pd and Rh amounting to 1 wt% total metal load were tested and the catalyst with 0.75 wt% Pd and 0.25 wt% Rh yielded the best results. Ecotoxicity and biodegradability (measured as BOD(5)/COD ratio) of the effluents were checked. A significant decrease of ecotoxicity was observed while biodegradability was dramatically improved from 0.02 for the initial 4-CP solution up to values higher than 0.6.
BACKGROUND The industrial application of ionic liquids (ILs) can induce the generation of wastewater and their release into the aquatic media. ILs can be efficiently removed by advanced oxidation processes (AOPs), which are expensive to implement. An alternative, using solar photocatalysis and biological degradation in combination, was used here to remove 1‐hexyl‐3‐methylimidazolium chloride (HmimCl) and 1‐butyl‐4‐methylpyridinium chloride (BmpyrCl). The chemical pretreatment allowed the ILs to be converted into by‐products for easier biodegradation in a sequential batch reactor (SBR). RESULTS Photocatalytic degradation, using 0.25 g TiO2 L−1 and 600 W m−2 solar radiation for 24 h, allowed a complete ILs removal and a partial mineralization of the organic matter, 28% for Bmpyr+ and 35% for Hmim+. A degradation pathway based on the by‐products identified was proposed for each IL. The reaction effluents were submitted to a biological treatment in an SBR, using organic loading rates of 0.18–0.2 kg COD kg−1 VSS d−1 and a biomass concentration of 3.5 g VSS L−1 in 8 h cycles. The combined treatment allowed highly efficient removal of organic matter [total organic carbon (TOC) conversion exceeded 75% for HmimCl and 78% for BmpyrCl]. CONCLUSION Solar photocatalytic oxidation efficiently removed ILs and produced more biodegradable and less ecotoxic effluents. Biological oxidation increased TOC and chemical oxygen demand (COD) removal to more than 75% for the overall treatment. Combining solar photocatalysis and biological degradation therefore provided an effective system for IL removal. © 2019 Society of Chemical Industry
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