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Report as of FY2006 for 2006PR28B: "Use of Waste Tire
Crumb Rubber to Remove Inorganic (Arsenic, Mercury) and
Polycyclic Aromatic Hydrocarbons (PAHs) Species from
Aqueous Solutions"

Alamo Luis; Perales, Oscar; Roman, Felix, 2007, Sorption of ethylbenzene, toluene and xylene onto crumb rubber from aqueous solutios Sorption of ethylbenzene and xylene in CLEANTECH, NSTI, Santa Clara, CA, p. 22-36.
Perales, Oscar; Roman, Felix; Alamo, Luis; Sanchez, Diana; Cruz, Jose, 2007,Evaluan nuevas opciones para reciclaje de goma, GACETA OF THE U OF PUERTO RICO AT MAYAGUEZ (V9, Y1,January07) (in Spanish) Perales, Oscar; Roman, Felix; Alamo, Luis; Sanchez, Diana; Cruz, Jose; 2007, Evaluan nuevas opciones para reciclaje de goma, DIALOGO (MAGAZINE OF THE UNIVERSITY OF PUERTO RICO). February07. Sanchez, Diana; Roman, Felix; Perales, Oscar 2007, Removal of Copper Ions from Aqueous solutions using waste tire crumb rubber as sorbent PRISM 2007, Cayey, PR (poster presentation) Alamo, Luis; Roman, Felix; Sanchez, Diana; Perales, Oscar, Jose, 2007, Use of recyled crumb rubber to remove organic pollutants from aqueous solutions, PRISM 2007, Cayey, PR (poster presentation) Torres, Heidy; Roman, Felix; Alamo, Luis; Perales, Oscar, 2007 Comparison between GC-MS Ion Trap, GC-MS Quadrupole and GC-FID techniques used in sorption studies of xylene onto crumb rubber, PRISM 2007, Cayey, PR (oral presentation) Lopez, Jose; Nieto, Sorelis; Perales, Oscar; Roman, Felix; 2007, Sorption of Tetracycline onto waste tire crumb rubber, PRISM 2007, Cayey, PR (poster presentation) Alamo, Luis; Sanchez Diana; Perales, Oscar; Roman, Felix, 2007, Use of recycled crumb rubber to remove inorganic and organic contaminants from aqueous solutions, EXPOCHEM 2007, Mayaguez,, PR (poster presentation) Lopez, Jose; Nieto, Sorelis; Perales, Oscar; Roman, Felix, 2007, Sorption of Tetracycline onto waste tire crumb rubber, EXPOCHEM 2007, Mayaguez, PR (poster presentation) Alamo, Luis; Sanchez, Diana; Roman, Felix; Perales, Oscar, 2007, Sorption of ethylbenzene, toluene and xylene onto crumb rubber from aqueous solutios, ACS 233rd National Meeting & Exposition, Chicago, March 25-29, 2007 Lopez, Jose; Sanchez, Diana; Alamao, Luis; Perales, Oscar; Roman, Felix, 2007, Renoval of tetracycline, organic solvents and metal ions from from Aqueous solutions using waste tire crumb rubber as sorbent, USDA, Mayo 2007, Washington DC, (poster presentation) Alamo, Luis; Perales, Oscar; Roman, Felix 2007, Sorption of ethylbenzene, toluene and xylene onto crumb rubber from aqueous solutions, CLEANTECH, Santa Clara, CA, May 24-25, 2007 Alamo, Luis, 2006, Sorption of ETX from aqueous solutions, MS Thesis, Dept. of Chemistry, UPR-Mayaguez, Mayaguez, Puerto Rico, 100 pages Nieto, Sorelis, 2006, Removal of antimicrobials from aqueous solutions, MS Thesis, Dept. of Chemistry, UPR-Mayaguez, Report Follows
Problem and Research Objectives:Protecting water bodies from contamination is essential for health and safety. Typical inorganicpollutants are heavy metals that form highly soluble solid products (e.g., Hg), or no solid at all(As-oxyanions like arsenite and arsenate), after conventional alkaline precipitation.
limitations of conventional approaches become more evident at very dilute concentrations ofcontaminants as those observed in effluents from water treatment plants using conventionalalkaline treatment, or ground waters polluted by hazardous species mobilized by leaching and/orpercolation throughout soil substrates. Optional solvent extraction and ionic exchange systems arevery expensive and they are tailored for high ion selectivity, which limits the removal of allcontaminants in a single-step operation. In Puerto Rico, main problems of heavy metal pollution(e. g., Pb and Cd) have been reported in different types of effluents. The mercury pollutionproblem in Juncos and the presence of lead in some wells in Gurabo are also examples of theaquifers contamination issue.
Polycyclic Aromatic Hydrocarbons (PAHs) are a group of more than a hundred organiccompounds composed of two or more carbon rings derived from benzene. These compounds havereceived a significant attention due to their suspected mutagenic and carcinogenic nature. PAHsarise mostly form incomplete combustion processes and are ubiquitous in the environment. Themain outdoor sources of PAHs include combustion from gasoline and diesel engines, combustionof coal and oil for power generation, wood burning and incineration, among others. In turn,major indoors sources of PAHs include cooking, smoking, and burning of natural gas andincense. Indoor PAH concentrations in air as high as 1000 ng/m3 and 110 ng/m3 for 2 memberrings-PAH have been reported in Japan and USA. It has been confirmed that PAHs can enterwater directly from the air with dust and precipitation, or on particles washed from the soil byrunoff. PAHs dissolved in water can be "taken up" by plants, and are released into soil and waterwhen the plants die, decompose or are burned. PAHs can also be mobilized into the aquaticenvironment through discharges from industrial and domestic sewage effluents, leaks of PAHs-containing materials (e.g. oils), runoff from paved roads, parking lots, and the grounds of woodpreservation plants, among other sources. Accordingly, the development of a low-cost,environmental friendly and efficient removal process for PAHs compounds from effluents (gasand water) becomes indispensable.
In the United States, approximately 240 million tires were discarded in 1990 on the basis of thetire industry’s estimation (U.S. EPA, 1991) and it has been suggested that discarded tires reaches10 billion every year, worldwide. In 2001, the United States generated approximately 273-millionscrap tires. Although, markets now exist for 76% of these scrap tires –up from 17% in 1990- theremaining are still stockpiled, or land filled. On a local basis, over 4-million tires are discardedannually in Puerto Rico. It represents near to 15,000 tires per day, which makes the problem ofsolid waste management even more difficult to handle. Approximately 800,000 tires are reusedeach year, the remainder is land filled or illegally dumped. Stockpiled scrap tires pose potentiallyserious health and safety problems. Whole tires served as breeding grounds for diseases carryingmosquitoes and rodents. Also, tire piles are fire hazards and, once ignited, they can burn out ofcontrol for months, producing acrid black smoke and a hazardous oily residue. Widespread illegaldumping poses the same problem associated with stockpiling. Thousands of abandoned scraptires are found in streams, rivers and roadsides throughout the Island. The mismanagement ofmillions of scrap tires every year represents a significant waste of resources. A very recentexample is the case of the 8,000 tons of chopped-up tires in the barge docked in Guayama sinceJuly 23rd, 2002, a problem without a definitive solution, at least in the short term.
Based on the above premises, the search of alternatives to expand the re-use possibilities forwaste tires sounds justified. The present proposal addressed the systematic evaluation of crumbrubber as a suitable material to remove extremely toxic PAHs compounds from aqueous solutionsthrough a low-cost and easy-to-scale technology based on the sorption properties of this waste material. The present remediation option is based on the presence of carbon black, zinc oxide, andsulfur in crumb rubber, with potential capability to absorb/adsorb hazardous species from wateror gaseous streams. This fact has been verified in preliminary results reported in our previousworks where the very efficient removal of inorganic Cu(II), Cd(II) and Pb(II) as well as organicBTEX (ethylbenzene, xylene, toluene) species have been demonstrated. Sorbent waste tire crumbrubber will be kindly provided by Rubber Recycling and Manufacturing Corp., REMA, a PuertoRican company that produces crumb rubber at different particle sizes from scrap tires.
Accordingly, the present proposal dealt with the detailed study of the sorption capability of wastetire crumb rubber for PAHs compounds, e. g. naphthalene, among others, of environmentalconcern. We proposed to investigate the conditions leading to maximization of uptake capacityand sorption rate, a factor of critical importance to determine the potential use of the proposedsorbent on a large scale remediation application.
Granular crumb rubber, screened at different mesh sizes, was provided by REMA Corp. a tirerubber recycling company located in Caguas, Puerto Rico.
1 Chemical stability of granular crumb rubberThe behavior of crumb rubber in aqueous solutions at different pH values and particle sizes hasbeen evaluated already. It has been verified that crumb rubber do not release any toxic inorganicspecies into the aqueous phase.
2 Sorption tests in aqueous phaseThe basic set-up for the sorption tests includes temperature-controlled water shaker baths, stirrers,pH-meters and filtration systems, drying ovens and GC/MS and available in Roman’s laboratory. The term sorption here is used to include both adsorption, which
refers to the retention of solutes by the surfaces of a solid material, and absorption, which refers
to the retention of the solutes within the polymeric matrix. Sorption processes result from
physical, chemical and electrostatic interactions between the solid surfaces and the sorbate.
In PAHs sorption tests screw cap vials with Teflon-lined septa were used instead of common
glass beakers and agitated on a hematological mixer until equilibrium will be reached. In order to
minimize vapor loss and allow a suitable mixing, the head space in the vial after addition of the
sorbent and sorbate, was kept at approximately 1 ml. HgCl2 was employed as a biocide to avoid
degradation of the organic compounds by bacteria or fungi. Vials will be samples periodically
and analyzed for PAHs. Solid Phase Microextraction (SPME), GC/MS and LC/MS were used to
determine the concentration of the PAH in the initial solution and at the end of the sorption stage.
During the first step of the experimental work, the sorbent was contacted with solutions
containing single species. The results of the experimental work permitted to determine the
equilibrium uptake, sorption rates, and removal efficiency.
Once the optimum conditions for the quantitative determination of PAHs by the GC-MStechniques were determined, our experimental work was focused on the evaluation of thesorption behavior of the following PAHs: phenanthrene (PN), acenaphtylene (ACN) andacenaphthene(ACNP) from aqueous solutions under room-temperature conditions. Inorder to minimize any loose of the PAHs by volatilization, all experiments were carriedout at a fixed concentration of PAHs (500 ppb for PN and 900 ppb for CAN and ACNP).
The solution pH was kept constant at 6.0. The concentration of crumb rubber (mesh 14-20) was varied between 0.03 g/L and 10 g/L in all tests. The terminal concentrationvalues (i.e., the concentration at the equilibrium) were used to determine the removalefficiency of the crumb rubber. Experimental values were fitted to Langmuir andFreundlich isotherms. In general, the sorption behavior of all systems was well describedby Freundlich’s equation.
The higher concentrations of crumb rubber (10 g/L and 5 g/L) allowed both, the highestremoval efficiencies and extremely short contact times. For instance, 99.2% and 98.8% ofPN was removed at the end of 30 minutes of contact for 10 g/L and 5 g/L of crumbrubber, respectively. The corresponding terminal concentrations were 4.2 ppb and 5.8ppb. The equilibrium conditions were achieved only after 28 hours when theconcentration of crumb rubber was 0.01 g/L. The removal efficiency was 77% (114 ppbof PN in the final solution). The experimental data were well fitted by Freundlichequation (r=0.988).
In the case of CAN, two hours were required to achieve a 95% removal when the crumbrubber concentration was 10g/L. The removal dropped to 55% (20 hours of contact) when0.03 g/L of crumb rubber was used instead. Again, the terminal concentration were wellfitted by both Langmuir (r=0.9994) and Freundluch (r=0.9969) isotherms.
Crumb rubber was also an excellent sorbent to remove ACNP from aqueous solutions.
The terminal concentration of ACNP was as low as 18 ppb (from starting 900 ppb ACNPsolutions) after 2 hours of contact and 10g/L of crumb rubber. The correspondingremoval efficiency was 98%. Only 76% of starting ACNP was removed after 20 hourswhen 0.03 g/L of crumb rubber was employed. Langmuir (r=0.9769) and Freundlich(r=0.9854) equations fitted experimental data very well.
Based on the above comments, the capability and efficiency of waste tire crumb rubber(mesh 14-20) to remove the selected PAHs compounds have been experimentallyverified. Obtained results suggest that crumb rubber can be considered an excellentsorbent to clean-up aqueous effluents polluted by PAHs compounds. Ongoing work willaddress the evaluation of the sorption behavior under competitive conditions (co-existence of two and three PAHs compounds in the same solution) in batch andcontinuous (column) tests.


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