Feasibility study on cross-linked biopolymeric concrete encapsulating selenium glass wastes.

Feasibility study was conducted to encapsulate the selenium (Se) contained in glass waste, using the biopolymer-modified concrete. Biopolymer has unique characteristics to provide the chemical sites to metals or toxic compounds through the three-dimensional cross-linked structure. Very minute amount of biopolymer enhanced the characteristics of cementitious material. The resulting biopolymeric composite with selenium glass waste showed 20% higher compressive strength than ordinary concrete and the lower leaching concentration than the equipment detection limit. For a qualitative measurement, X-ray diffraction (XRD; X-ray powder diffractogram) was used to characterize the biopolymeric concrete. The optimum waste content percentage with appropriate biopolymer concrete mixture ratio was identified for its possible commercial use.

Naval derusting wastewater containing high concentration of iron, treated in UV photo-Fenton-like oxidation.

The UV photooxidation with Fe(III) and H2O2 was employed to treat a naval derusting wastewater, which contains the high COD (chemical oxygen demand) and various metal concentrations exceptionally with high concentrations of citric acid and iron. Because of its iron containment, the Fenton-like reaction automatically took place with the added amount of H2O2. The decomposition rate was found in a sequence of: UV/H2O2/Fe(III) > UV/H2O2 > Fe(II)/H2O2. Two H2O2 injection methods, single and multiple points, were evaluated. The multiple-point H202 injection was more efficient to decompose the citric acid. The decomposition of the synthetic citric acid and the real derusting citric acid wastewater was also compared. The 93% COD reduction of the derusting wastewater was achieved using the UV/H2O2/Fe(III) treatment.

WITHDRAWN: Reductive dechlorination of PCB by ultrasound-assisted chemical process.

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Encapsulation of lead from hazardous CRT glass wastes using biopolymer cross-linked concrete systems.

Discarded computer monitors and television sets are identified as hazardous materials due to the high content of lead in their cathode ray tubes (CRTs). Over 98% of lead is found in CRT glass. More than 75% of obsolete electronics including TV and CRT monitors are in storage because appropriate e-waste management and remediation technologies are insufficient. Already an e-waste tsunami is starting to roll across the US and the whole world. Thus, a new technology was developed as an alternative to current disposal methods; this method uses a concrete composite crosslinked with minute amounts of biopolymers and a crosslinking agent. Commercially available microbial biopolymers of xanthan gum and guar gum were used to encapsulate CRT wastes, reducing Pb leachability as measured by standard USEPA methods. In this investigation, the synergistic effect of the crosslinking reaction was observed through blending two different biopolymers or adding a crosslinking agent in biopolymer solution. This CRT-biopolymer-concrete (CBC) composite showed higher compressive strength than the standard concrete and a considerable decrease in lead leachability.

Mechanism and kinetics of reductive dehalogenation of PBB (polybrominated biphenyl) in the sonolytic and ketyl radical system.

The kinetics and mechanism of reductive destruction of aqueous polybrominated biphenyl (PBB) were studied. Complete degradation was achieved within 30 min of ultrasound-assisted chemical process (UACP), which involved sonication, ketyl radical and its anion, and metal catalyst (ferrous ion). Reductive dehalogenation of PBB is a first-order reaction between PBB concentration and UACP reaction time. The kinetic condition of PBB degradation was optimized in terms of temperature, dosage of radical initiator, and metal catalyst. Mechanism of reductive debromination was also proposed to explain the function of ketyl and aryl radicals on the debromination of bromobiphenyl. Two kinetic models were studied to elucidate the debromination mechanism pathway. Laboratory observed data were found to fit model predicted values obtained from equilibrium and differential equations.

Surface characterization of adsorbents in ultrasound-assisted oxidative desulfurization process of fossil fuels.

Surface properties of two different phases of alumina were studied through SEM images. Characterization of amorphous acidic alumina and crystalline boehmite by XRD explains the differences in adsorption capacities of each sample. Data from small angle neutron scattering (SANS) provide further results regarding the ordering in amorphous and crystalline samples of alumina. Quantitative measurements from SANS are used for pore size calculations. Higher disorder provides more topological traps, irregularities, and hidden grooves for higher adsorption capacity. An isotherm model was derived for adsorption of dibenzothiophene sulfone (DBTO) by amorphous acidic alumina to predict and calculate the adsorption of sulfur compounds. The Langmuir-Freundlich model covers a wide range of sulfur concentrations. Experiments prove that amorphous acidic alumina is the adsorbent of choice for selective adsorption in the ultrasound-assisted oxidative desulfurization (UAOD) process to produce ultra-low-sulfur fuel (ULSF).

Evaluation of biopolymer-modified concrete systems for disposal of cathode ray tube glass.

Cathode ray tubes (CRTs) from computer monitors and television sets, which contain significantly high percentage of lead (Pb) by weight, represent an enormous and growing hazardous waste problem in the United States and worldwide. As a result, new technologies are needed to cope with current CRT waste stream and increased hazard and build new markets for its recycled components, developing commercially viable concrete composites, as well as minimizing CRT disposal problems. In this study, commercially available biopolymers, such as xanthan gum, guar gum, and chitosan, were used to encapsulate CRT glass waste, reducing the Pb leachability. The biopolymers utilized contain a number of useful functional groups, such as carboxyl (xanthan), hydroxyl (guar), and amino groups (chitosan), which play important roles in binding and stabilizing Pb onto concrete structures. The use of biopolymers in concrete systems can create a stable interpenetrating cross-linking composite that will last for many years. Results from these new composites show 30% higher compressive strength than standard concrete and a sharp decrease in lead leachability from several thousand milligrams per liter initially to an amount of three-tenths milligrams per liter or lower values (much lower than the U.S. Environment Protection Agency standard for hazardous waste of 5 mg/L by the toxicity characteristic leaching procedure test), and for some of the composites leachability is below even the standard for drinking water. This efficient and cost-effective CRT-biopolymer-concrete composite is a new class of biopolymer-modified material that can potentially perform a significant role in relieving the current CRT issue.