Juan Jáuregui-Rincón

On the importance of surface chemistry and composition of Bone char for the sorption of heavy metals from aqueous solution

AbstractThis paper reports new insights on the role of the inorganic composition of Bone char (BC) on its sorption properties for the removal of heavy metals Cd2+, Ni2+, and Zn2+ ions from aqueous solution. In particular, we showed the importance of both composition and surface chemistry of BC on its sorption properties for the removal of these metal ions in aqueous solution. Results of physicochemical characterization and sorption studies suggest that the inorganic phase of BC may contribute from 60 to 92% of the sorption process of heavy metals in aqueous solution. In particular, the ion exchange process of Ca2+ involving the hydroxyapatite has an important contribution in heavy metal removal using bone char. BC is an outstanding sorbent for the removal of Ni2+ ions and appears to be suitable for water purification systems.

High removal of chemical and biochemical oxygen demand from tequila vinasses by using physicochemical and biological methods

The goal of this research is to find a more effective treatment for tequila vinasses (TVs) with potential industrial application in order to comply with the Mexican environmental regulations. TVs are characterized by their high content of solids, high values of biochemical oxygen demand (BOD 5), chemical oxygen demand (COD), low pH and intense colour; thus, disposal of untreated TVs severely impacts the environment. Physicochemical and biological treatments, and a combination of both, were probed on the remediation of TVs. The use of alginate for the physicochemical treatment of TVs reduced BOD 5 and COD values by 70.6% and 14.2%, respectively. Twenty white-rot fungi (WRF) strains were tested in TV-based solid media. Pleurotus ostreatus 7992 and Trametes trogii 8154 were selected due to their ability to grow on TV-based solid media. Ligninolytic enzymes’ production was observed in liquid cultures of both fungi. Using the selected WRF for TVs’ bioremediation, both COD and BOD 5 were reduced by 88.7% and 89.7%, respectively. Applying sequential physicochemical and biological treatments, BOD 5 and COD were reduced by 91.6% and 93.1%, respectively. Results showed that alginate and selected WRF have potential for the industrial treatment of TVs.

Iron effect on the fermentative metabolism of Clostridium acetobutylicum ATCC 824 using cheese whey as substrate

Butanol is considered a superior liquid fuel that can replace gasoline in internal combustion engines. It is produced by acetone-butanol-ethanol (ABE) fermentation using various species of solventogenic clostridia. Performance of ABE fermentation process is severely limited mostly by high cost of substrate, substrate inhibition and low solvent tolerance; leading to low product concentrations, low productivity, low yield, and difficulty in controlling culture metabolism. In order to decrease the cost per substrate and exploit a waste generated by dairy industry, this study proposes using cheese whey as substrate for ABE fermentation. It was observed that the addition of an iron source was strictly necessary for the cheese whey to be a viable substrate because this metal is needed to produce ferredoxin, a key protein in the fermentative metabolism of Clostridium acetobutylicum serving as a temporary electron acceptor. Lack of iron in the cheese whey impedes ferredoxin synthesis and therefore, restricts pyruvate-ferredoxin oxidoreductase activity leading to the production of lactic acid instead of acetone, butanol and ethanol. Moreover, the addition of FeSO4 notably improved ABE production performance by increasing butanol content (7.13 ± 1.53 g/L) by 65% compared to that of FeCl3 (4.32 ± 0.94 g/L) under the same fermentation conditions.

Assessment of the quality and toxicity of the discharges of a wastewater treatment plant and alternatives to improve its operation.

Wastewater discharges into freshwater bodies represent a serious ecological problem worldwide. In underdeveloped and developing countries wastewater treatment plants (WTP) only count with basic treatment, leading to the pollution of important aquatic reservoirs causing critical situations. In the present work, a one year evaluation of toxicity and main physical and chemical parameters of one of the major WTP of the state of Aguascalientes was conducted fortnightly, and to assess treatment alternatives for this WTP we tested: a) three white rot fungi (WRF), b) a photo-electrochemical process, c) ion-exchangers resins and activated carbon. The 3 WRF exhibited high COD removal from influents (72 – 95 %) but only Phanerochaete chrysosporium reached significant toxicity removals (70 and 55 %, for an influent and an effluent, respectively). Treatments with electrochemical advanced oxidation processes resulted with the highest toxicity and COD removals (96 % for both parameters) in comparison to biological and physicochemical treatments. Adsorption with activated carbon, zeolite and chelex ion-exchange resins removed 60 – 90 % of COD and 60 – 99 % toxicity. These results could be used to improve operation of the Industrial Park WTP and to plan future modifications to the plant.

SYNTHESIS AND CHARACTERIZATION OF AMINATED COPOLYMERS OF POLYACRYLONITRILE-GRAFT-CHITOSAN AND THEIR APPLICATION FOR THE REMOVAL OF HEAVY METALS FROM AQUEOUS SOLUTION

Aminated copolymers of polyacrylonitrile-graft-chitosan (APANCS) were synthesized via the reaction of copolymers of polyacrylonitrile-graft-chitosan (PAN-g-CS) with diethylenetriamine in solution. Specifically, copolymers of PAN-g-CS have been obtained via a graft polymerization method using acrylonitrile (AN), chitosan (CS) and a free-radical initiating process with ceric ammonium nitrate (CAN) as initiator under air presence. Superficial structure of these copolymers was modified using amination reactions to introduce amine groups on its polymeric matrix. This polymer (APANCS) was applied in the removal of Pb2+, Cd2+ and Zn2+ ions in aqueous solutions. Samples of PAN-g-CS and APANCS were characterized by FT-IR spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, TGA, DSC and gravimetric analyses. Results of this study suggest that the amine groups of the structure of chitosan are involved in the grafting process onto the polymeric matrix of polyacrylonitrile. On the other hand, the adsorption capacities for heavy metal removal of this polymer were significantly improved using the chemical modification with amination reactions. Specifically, this polymeric material showed a maximum adsorption of 12.93, 2.27 and 2.10 mg/g at pH 5 for the removal of Pb2+, Cd2+ and Zn2+ ions, respectively.

Zimm-Bragg Model Applied to Sorption of Dyes by Biopolymers: Alginic Acid and Xanthan

Dyes and dyeing processes are widely used as a means of introducing color into fibers or fabrics. Dyes should be easily introduced into the fiber and then, the color must be reasonably permanent (wash-fast) and stable to light (light-fast). Dyes exhibit considerable structural diversity and are classified by their chemical structure, application to the fiber type and/or solubility. A general classification accommodates these compounds as anionic (acid, direct and reactive dyes); cationic (basic dyes); and non ionic (disperse dyes). Disperse Yellow 54 (DY54) is a typical dye which can be used in dispersed form to color polyester, polyamides, nylon, acrylic fibers and plastics. Direct Black 22 (DB22) is a cationic compound (at neutral pH) that imparts color to cotton, cellulose, leather, wool and silk (Holme, 2000; Ali, 2005). The chemical structures of DY54 and DB22 are represented in table 1. Despite the fact that supercritical methods (Ozcan et al., 1997; Joung & Yoo, 1998; Guzel and Akgerman, 1999; Lee et al., 1999; Sung & Shim, 1999; Shinoda and Tamura, 2003; Hou & Dai, 2005) have been developed to improve the performance of dyeing processes, still conventional (dye baths) methods are widely used (Holme, 2000). During dyeing processes great amounts of unfixed dyes (which vary considerably depending on dye-fiber affinity and dyeing process parameters) may be lost to the effluent. The release of these effluents in water streams results in serious environmental impacts. The development of an environmentally benign methodology for the removal of dyes from textile wastewaters still represents a major technological challenge. It is well known that textile industries, pulp mills and dyestuff manufacturing discharge highly colored wastewaters which represent an aesthetic problem and reduce photosynthetic activity in the receiving water into which they are discharged. Nowadays, many dyes are designed for their chemical stability (wash and light fastness) and do not undergo biochemical degradation readily. For instance, anthraquinone based dyes are more resistant to biodegradation (oxidation rates are very slow) due to their fused aromatic structures (Baughman & Weber, 1994). Since azo dyes are the most widely used, several degradation methods have been implemented to remove them from water, among them, anaerobic treatments predominate. The main drawbacks of this approach are its elevated cost and the production of carcinogenic aromatic amines which limits macro-scale application (Ogawa & Yatome, 1990; Knapp & Newby, 1995; Weber & Adams, 1995).