Separation of cellulose from industrial paper mill wastewater dried sludge using a commercial and cheap ionic liquid.

Industrial wastewaters and their treatment are now placed at the heart of the environmental concerns that industries face. Some research work has been carried out in order to limit the impact of these wastes on the environment as well as their costs. In this study, wastewater dehydrated sludge (55% wt. water content) from the paper industry was used to recover cellulose by using tetrakis(hydroxymethyl)phosphonium chloride, [P(CH2OH)4]Cl, ionic liquid as a solvent. The ionic liquid has shown remarkable results in terms of cellulose extraction in addition to its non-volatility and lower toxicity compared to organic volatile solvents. All cellulose, based on dry sludge, was recovered from the industrial dehydrated sludge with better operation conditions. The influence of temperature and the quantity of ionic liquid was preliminary studied in order to optimise the extraction conditions.

Towards advanced aqueous dye removal processes: a short review on the versatile role of activated carbon.

During the last decade, several physico-chemical and biological techniques have been developed to remove colour from textile wastewaters. Some of these techniques rely on and many will profit from activated carbon (AC). The role of AC is versatile: (1) it acts as a dye adsorbent, not only in straightforward adsorption processes but also in AC-enhanced coagulation and membrane filtration processes; (2) it generates strong oxidising agents (mostly, hydroxyl (OH) radicals) in electrochemical dye oxidation; (3) it catalyses OH production in advanced oxidation processes; (4) it catalyses anaerobic (azo) dye reduction and supports biofilm growth in microbial dye removal. This paper reviews the role of AC in dye decolourisation, evaluates the feasibility of each AC-amended decolourisation technique and discusses perspectives on future research.

Compact Carbon-Based Membrane Reactors for the Intensified Anaerobic Decolorization of Dye Effluents.

Carbon-based membranes integrated with anaerobic biodegradation are presented as a unique wastewater treatment approach to deal with dye effluents. This study explores the scope of ceramic-supported carbon membrane bioreactors (B-CSCM) and ceramic-supported graphene oxide membrane bioreactors (B-CSGOM) to decolorize azo dye mixtures (ADM) and other dyes. The mixture was prepared using an equimolar composition of monoazo Acid Orange 7, diazo Reactive Black 5, and triazo Direct Blue 71 dye aqueous solution. Afterwards, as in the ADM experiment, both compact units were investigated for their ability in the biodecolorization of Methylene Blue (MB) and Rhodamine B (RhB) dye solutions, which do not belong to the azo family. The obtained outcomes revealed that the conductive surface of the graphene oxide (GO) membrane resulted in a more efficient and higher color removal of all dye solutions than B-CSCM under a wide feed concentration and permeate flux ranges. The maximum color removal at low feed concentration (50 mg·L-1) and permeate flux (0.05 L·m-2·h-1) was 96% for ADM, 98% for MB and 94% for RhB, whereas it was 89%, 94% and 66%, respectively, for B-CSCM. This suggests that the robust, cost-effective, efficient nanostructures of B-CSGOM can successfully remove diverse azo dye solutions from wastewater better than the B-CSCM does.

Elimination of phenol and aromatic compounds by zero valent iron and EDTA at low temperature and atmospheric pressure.

This work deals with a new abiotic oxidation process designed as a suitable pre-treatment step within a biological depuration of wastewater containing phenol or its derivatives (o-cresol, 2-chlorophenol and p-nitrophenol) or aniline. The reaction was carried out in a stirred tank reactor at 20 degrees C and atmospheric pressure in presence of the organic compound, 150mgl(-1), zero valent iron particles (10g), ethylenediamine tetraacetic acid (EDTA, 101mgl(-1)) and air. The experimental results show that 85% of phenol conversion can be achieved after 360min. 2-Chlorophenol was found to be more easily degradable and it is completely eliminated after 300min. The oxidation of o-cresol and aniline behaved more closely to phenol obtaining after 360min 70% and 68% of conversion respectively. p-Nitrophenol was a very refractory compound, giving only 28% of conversion after 360min. Moreover, the influence of some operating variables was studied over the following ranges: temperature from 20 to 50 degrees C, initial phenol concentration from 150 to 1000mgl(-1), EDTA concentration from 50 to 200mgl(-1) and iron particles from 5 to 20g. As expected, temperature strongly enhances phenol conversion. Also, an increase of the catalyst to phenol ratio or the iron or EDTA to phenol ratio improves the reaction rate. A preliminary kinetic analysis of the data shown that the rate of phenol disappearance is not first order with respect to the phenol.

Integrated catalytic wet air oxidation and aerobic biological treatment in a municipal WWTP of a high-strength o-cresol wastewater.

This study examines the feasibility of coupling a Catalytic Wet Air Oxidation (CWAO), with activated carbon (AC) as catalyst, and an aerobic biological treatment to treat a high-strength o-cresol wastewater. Two goals are pursued: (a) To determine the effect of the main AC/CWAO intermediates on the activated sludge of a municipal WasteWater Treatment Plant (WWTP) and (b) To demonstrate the feasibility of coupling the AC/CWAO effluent as a part of the influent of a municipal WWTP. In a previous study, a high-strength o-cresol wastewater was treated by AC/CWAO aiming to establish the distribution of intermediates and the biodegradability enhancement. In this work, the biodegradability, toxicity and inhibition of the most relevant intermediates detected in the AC/CWAO effluent were determined by respirometry. Also, the results of a pilot scale municipal WWTP study for an integrated AC/CWAO-aerobic biological treatment of this effluent are presented. The biodegradation parameters (i.e. maximum oxygen uptake rate and oxygen consumption) of main AC/CWAO intermediates allowed the classification of the intermediates into readily biodegradable, inert or toxic/inhibitory compounds. This detailed study, allowed to understand the biodegradability enhancement exhibited by an AC/CWAO effluent and to achieve a successful strategy for coupling the AC/CWAO step with an aerobic biological treatment for a high-strength o-cresol wastewater. Using 30%, as COD, of AC/CWAO effluent in the inlet to the pilot scale WWTP, the integrated AC/CWAO-biological treatment achieved a 98% of total COD removal and, particularly, a 91% of AC/CWAO effluent COD removal without any undesirable effect on the biomass.

A potential application of sludge-based catalysts for the anaerobic bio-decolorization of tartrazine dye.

Two highly efficient (K2CO3/sludge carbon and ZnCl2/sludge carbon) solids were prepared by chemical addition following carbonization at 800 °C and were tested for anaerobic reduction of tartrazine dye in a continuous upflow packed-bed biological reactor, and their performance was compared to that of commercial activated carbon (CAC). The chemical and structural information of the solids was subjected to various characterizations in order to understand the mechanism for anaerobic decolorization, and efficiency for SBCZN800 and SBCPC800 materials was 87% and 74%, respectively, at a short space time (τ) of 2.0 min. A first-order kinetic model fitted the experimental points and kinetic constants of 0.40, 0.92 and 1.46 min(-1) were obtained for SBCZN800, SBCPC800 and CAC, respectively. The experimental results revealed that performance of solids in the anaerobic reduction of tartrazine dye can depend on several factors including chemical agents, carbonization, microbial population, chemical groups and surface chemistry. The Langmuir and Freundlich models are successfully described in the batch adsorption data. Based on these observations, a cost-effective sludge-based catalyst can be produced from harmful sewage sludge for the treatment of industrial effluents.

TiO2-sludge carbon enhanced catalytic oxidative reaction in environmental wastewaters applications.

The enhanced oxidative potential of sludge carbon/TiO2 nano composites (SNCs), applied as heterogeneous catalysts in advanced oxidation processes (AOPs), was studied. Fabrification of efficient SNCs using different methods and successful evaluation of their catalytic oxidative activity is reported for the first time. Surface modification processes of hydrothermal deposition, chemical treatment and sol-gel solution resulted in improved catalytic activity and good surface chemistry of the SNCs. The solids obtained after chemical treatment and hydrothermal deposition processes exhibit excellent crystallinity and photocatalytic activity. The highest photocatalytic rate was obtained for the material prepared using hydrothermal deposition technique, compared to other nanocomposites. Further, improved removal of bisphenol A (BPA) from aqueous phase by means of catalytic ozonation and catalytic wet air oxidation processes is achieved over the solid synthesized using chemical treatment method. The present results demonstrate that the addition of TiO2 on the surface of sludge carbon (SC) increases catalytic oxidative activity of SNCs. The latter produced from harmful sludge materials can be therefore used as cost-effective and efficient sludge derived catalysts for the removal of hazardous pollutants.

Degradation of model olive mill contaminants of OMW catalysed by zero-valent iron enhanced with a chelant.

The aim of this study was to investigate the effect of a chelated zero valent iron as catalyst on the oxidation of six organic acids that are generally found in olive mill wastewater. The reaction was carried out in a stirred tank reactor under extremely mild conditions, a temperature of 30°C and atmospheric pressure. Solutions of 350 mg/L of the six organic compounds were treated individually using zero valent iron particles (15 g), nitrilotriacetic acid disodium salt (NTA, 100mg/L) and air. The efficiency of the process was evaluated to determine the organic compound conversion, the chemical oxygen demand (COD) reduction and the total organic carbon (TOC) reduction. The caffeic, 4-hydroxyphenylacetic and vanillic acids showed a total conversion after 180, 240 and 300 min of reaction, respectively. In turn, coumaric acid, tyrosol and cinnamic acid only reached conversions of 90, 87 and 68%, respectively, after 360 min of reaction. Four mixtures of the six acids with an initial total concentration of 1000 mg/L were also tested and gave an overall conversion of the organic compounds of 92-99% after 360 min of reaction. The COD conversions of the mixtures were always above 84%, but the TOC conversions values were lower, indicating a poorer mineralization.

Hydrolytic enzymes in activated sludge: extraction of protease and lipase by stirring and ultrasonication.

Hydrolytic enzymes released by the microorganisms in activated sludge are responsible for the organic matter degradation; however, the optimal extraction procedure of this valuable resource has not been well established until now. The present study evaluates the recovery of protease and lipase from the activated sludge by using stirring and ultrasonication, varying different parameters such as extraction time, concentration of additives (Triton X100, Cation Exchange Resin and Tris buffer), stirring velocity, ultrasonic power and sludge source. Sludge was collected from two urban wastewater treatment plants located in Prague (Czech Republic) and Reus (Spain). It was found that stirring using 2% v/v Triton X100 for 1h was enough to extract 57.4 protease units/g VSS, and that the same method using a combination of 10mM Tris pH 7.5+0.48 g/mL CER+0.5% TX100 as an additive allowed to extract 15.5 lipase units/g VSS from sludge collected from Reus Wastewater Treatment Plant. Ultrasonication allowed reducing the extraction time to 10 min for protease (using 2% v/v Triton X100 yielding 52.9 units/g VSS) and to 20 min for lipase (without any additive yielding nearly 21.4 units/g VSS), which makes this method appropriate for the extraction of enzymes from the activated sludge, and suitable to be scaled up for its application in the industry.

Supported Cu(II) polymer catalysts for aqueous phenol oxidation.

Supported Cu(II) polymer catalysts were used for the catalytic oxidation of phenol at 30 degrees C and atmospheric pressure using air and H(2)O(2) as oxidants. Heterogenisation of homogeneous Cu(II) catalysts was achieved by adsorption of Cu(II) salts onto polymeric matrices (poly(4-vinylpyridine), Chitosan). The catalytic active sites were represented by Cu(II) ions and showed to conserve their oxidative activity in heterogeneous catalysis as well as in homogeneous systems. The catalytic deactivation was evaluated by quantifying released Cu(II) ions in solution during oxidation, from where Cu-PVP(25) showed the best leaching levels no more than 5 mg L(-1). Results also indicated that Cu-PVP(25) had a catalytic activity (56% of phenol conversion when initial Cu(II) catalytic content was 200 mg L(Reaction)(-1)) comparable to that of commercial catalysts (59% of phenol conversion). Finally, the balance between activity and copper leaching was better represented by Cu-PVP(25) due to the heterogeneous catalytic activity had 86% performance in the heterogeneous phase, and the rest on the homogeneous phase, while Cu-PVP(2) had 59% and CuO/gamma-Al(2)O(3) 68%.