Remediation of Persistent Organic Pollutants Using a Novel Two-Phase Soil Washing Biosorption Process

A two-phase soil washing biosorption process was developed for the remediation of p,p-DDT-contaminated soil. The process involved desorption of contaminants from soil using dilute primary alcohols (40% 1-propanol) followed by contaminant removal from cosolvent solutions using fungal biosorption. Bench scale remediation studies were preformed to simulate ex situ (recycling experiment) or in situ (soil column study) treatment strategies. Both systems were effective at cleaning the soil to below Australian regulatory p,p-DDT levels. After 50–80 hours of soil washing, over 93% of p,p-DDT was removed from the soil(990 mg kg^-1 to <65 mg kg^-1) using either of these methods.p,p-DDT was removed from the cosolvent phase by sorption onto the fungal biomass. This resulted in only low levels of p,p-DDT remaining in the cosolvent solution(<1.5 mg l^-1). The application of both treatment strategies resulted in the rapid clean up of p,p-DDT-contaminated soil and the potential to recycle cosolvent solutions. The ability to recycle cosolvent solutions provides a mechanism for cost reductions of the remediation strategy.     

Partial characterization of the exopolysaccharide from Oscillatoria trichoides Szafer and the role of released polysaccharide in sequestration of Cr6+

The structural investigation and the chromium adsorptive potential of an exopolysaccharide (EPS) released during the growth of an indigenous cyanobacterium, Oscillatoria trichoides Szafer, were investigated in a laboratory‐scale study. The results showed that, of the total EPS produced, 410.53 milligrams/gram (mg g^?1) were released polysaccharides (RPS) and 11.36 mg g^?1 were capsular polysaccharides (CPS). The sorption of hexavalent chromium (Cr⁶⁺) by the RPS achieved a maximum amount of metal removal (q_max) value of 76.92 mg g^?1 of polysaccharide dry weight. The highest coefficient of determination (0.9742) for the Langmuir adsorption model indicates best fitness of the model in explaining the sorption as a unilayer process. Equilibrium studies indicated that 30 to 40 milligrams per liter initial chromium concentration and a pH of 2 were optimal for biosorption of chromium by the RPS. Scanning electron microscopy with energy‐dispersive X‐ray spectroscopy analysis of Cr⁶⁺‐treated RPS showed the presence of 3.76% bound chromium. Compositional analysis of the EPS showed the presence of carbohydrates, proteins, pyruvic acid, and hexosamines. High‐performance liquid chromatography analysis demonstrated the presence of hexoses, as neutral sugars and glucuronic acid as an acidic sugar. The presence of carboxylic groups was also detected by infrared spectroscopy. The presence of these chemical constituents may serve as binding sites for the metal ions; therefore, the RPS of this species appears to be a promising biosorbent for Cr⁶⁺.     

Heavy Metals Removal by Biosorption and Flotation

The removal of a mixture of heavy (toxic) metal cations (copper, nickeland zinc) from liquid effluents was investigated in this study at pilotscale, using counter-current contact mode. The innovative processinvolved the abstraction of metal ions onto fungal biosorbents, followedby the application of flotation for the subsequent solid/liquid separationof biomass particles. The ability of microorganisms to remove metal ionsfrom aqueous solutions is a well-known phenomenon. Nevertheless,engineering considerations are very important in decisions, concerningthe commercial future of biosorption and practical solutions are neededfor certain problems, such as the efficient post-separation ofmetal-loaded biomass. The two processes (flotation and biosorption) caneffectively operate in combination, in what it was termed biosorptiveflotation process. The sorbents may be recycled, after appropriate elutionof metals, as well as the treated (clean) water.     

Green algae of the genus Spirogyra: A potential absorbent for heavy metal from coal mine water

Algae have considerable capability for absorbing heavy metals from wastewaters and are considered an effective treatment technology. Heavy metal absorption from coal mine water from the Bhowra Abandoned mine (open cast mine) and the Sudamdih Shaft mine (underground mine waters), both located in Dhanbad, India, by cells of Spirogyra was studied at different dilutions (100 percent, 80 percent, 60 percent, 40 percent, and 20 percent). In the present study, the following 18 metals were selected for analysis: aluminium (Al), arsenic (As), silver (Ag), barium (Ba), beryllium (Be), bismuth (Bi), cadmium (Cd), cobalt (Co), chromium (Cr), cesium (Cs), copper (Cu), iron (Fe), gallium (Ga), indium (In), potassium (K), manganese (Mn), nickel (Ni), and vanadium (V). Accordingly, Al and K were found to be higher in concentration with respect to selected metals for both mine waters. The biosorption study revealed that higher amounts of Al, Bi, Co, Cs, Fe, Ga, Mn, Ni, and V were absorbed by algal biomass at 100 percent concentration from both mine waters. The maximum uptake of Cu, As, and Cd was measured at 60 percent, 40 percent, and 20 percent, respectively, for the Bhowra Abandoned mine water. The biosorption equilibrium study revealed that Ag, Al, Ba, Be, Bi, Co, Cr, Cs, Fe, Ga, In, K, Mn, Ni, and V were maximally absorbed by algal biomass at 100 percent concentration from Bhowra mine water, while the maximum uptake by the algal biomass measured for the Sudamidh coal mine water was for Al, As, Bi, Cu, Fe, and Mn at 100 percent concentration. The different physicochemical characteristics of mine water and drinking water standards was also studied. Accordingly, total dissolved solid and chemical oxygen demand concentrations exceeded the drinking water standards for water samples collected from both mines.     

Biosorptive removal of Pb(II) and Cu(II) from wastewater using activated carbon from cassava peels

The ability of activated carbon from cassava peels to remove heavy metals like Cu(II) and Pb(II) from hospital wastewater was investigated. The study showed that a pH of 8 was the best for the sorption of both metal ions onto the biosorbent. The time-dependent experiments for the metal ions showed that the binding of the metal ions to the biomass was rapid and occurred within 20–120 min. Sorption efficiency increased with a rise in adsorbent dosage. It increased from 12 to 73 % for Pb(II) and 26 to 79 % for Cu(II) when the adsorbent dose increased from 2 to 12 g. An increase in temperature led to an increase in sorption for both metal ions. The Langmuir model showed that the biomass has a higher sorption capacity for Cu(II) than Pb(II), with q _m = 5.80 mg g^?1 for Pb(II) and 8.00 mg g^?1 for Cu(II). The Freundlich isotherm K _f was 1.4 for Pb(II) and 1.8 for Cu(II), indicating a preferential sorption of Cu(II) onto the biosorbent. Adsorption capacity was found to decrease with an increase in particle sizes. Sorption occurred by physical mechanisms and was mainly controlled by intraparticle diffusion.     

Biosorption study of potential fungi for copper remediation from Peninsular Malaysia

The ability to grow in heavy metal contaminated areas and absorb heavy metals from the environment make fungi a potentially viable biological‐based technology for remediating hazardous heavy metals in soil. In this study, 10 fungi from a copper (Cu)‐polluted area in Malaysia were isolated, with the four highest growth fungi identified as Simplicillium subtropicum, Fusarium solani, Aspergillus tamari, and Aspergillus niger. Results from toxicity and biosorption testing showed that A. niger and F. solani grew the fastest in the presence of Cu, but exhibited lower Cu uptake per unit of biomoass. In contrast, A. tamarii and S. subtropicum had lower growth rates, but showed better uptake of Cu per unit of biomass. S. subtropicum was identified as the best species for bioremediation because it had the highest Cu uptake and positive growth measured in the presence of Cu at concentrations below 100 mg/L. A niger proved to be most suitable for bioremediation if the concentration of Cu exceeds 100 mg/L.     

Sorption of strontium on bentonite

Sorption of Sr on bentonite was studied using the batch technique. Distribution coefficients (K_d) were determined as a function of contact time, pH, sorbent and sorbate concentration and temperature. The data were interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich isotherms. Thermodynamic parameters for the sorption system were determined at three different temperatures. The positive value of the heat of sorption, ΔH° = 30.62 kJ/mol at 298 K, shows that the sorption of strontium on bentonite is endothermic. The negative value of the free energy of sorption, ΔG° = −10.69 kJ/mol at 298 K, shows the spontaneity of the reaction. ΔG° becomes more negative with increasing temperature, which shows that the sorption process is more favorable at higher temperatures. The mean free energy for sorption, E 9 kJ/mol, suggests that ion exchange is the predominant mode of sorption in the Sr concentration range studied, i.e. 0.01 – 0.3 mol/dm³. The presence of complementary cations depresses the sorption of strontium on bentonite in the order Ca²⁺>Mg²⁺>K⁺>Na⁺. Some organic complexing agents and natural ligands also affect the sorption of strontium. The desorption studies with ground water at low strontium loadings on bentonite show that about 90% of Sr is irreversibly sorbed on the bentonite.     

Treatment of simulated Reactive Yellow 22 (azo) dye effluents using Spirogyra species

The potential of commonly available green algae belonging to Spirogyra species was investigated as viable biomaterials for biological treatment of simulated synthetic azo dye (Reactive Yellow 22) effluents. The results obtained from the batch experiments revealed the ability of the algal species in removing the dye colour and was dependent both on the dye concentration and algal biomass. Maximum dye colour removal was observed on the third day for all the system conditions. Monitoring of ORP values helped to understand the overlying biochemical mechanism of algal-dye system. Based upon the results, the dye-algal treatment mechanism was attributed to biosorption (sorption of dye molecules over the surface of algal cells), bioconversion (diffusion of dye molecules into the algal cells and subsequent conversion) and biocoagulation (coagulation of dye molecules present in the aqueous phase onto the biopolymers released as metabolic intermediates during metabolic conversion of dye and subsequent settlement).     

Remedial options for chlorinated volatile organics in a partially anaerobic aquifer

A laboratory study was conducted for the selection of appropriate remedial technologies for a partially anaerobic aquifer contaminated with chlorinated volatile organics (VOCs). Evaluation of in situ bioremediation demonstrated that the addition of electron donors to anaerobic microcosms enhanced biological reductive dechlorination of tetrachloroethene (PCE), trichloroethene (TCE), and 1,1,1‐trichloroethane (1,1,1‐TCA) with half‐lives of 20, 22, and 41 days, respectively. Nearly complete reductions of PCE, TCE, 1,1,1‐TCA, and the derivative cis‐dichloroethene were accompanied by a corresponding increase in chloride concentrations. Accumulation of vinyl chloride, ethene, and ethane was not observed; however, elevated levels of ¹⁴CO₂ (from ¹⁴C‐TCE spiked) were recovered, indicating the occurrence of anaerobic oxidation. In contrast, very little degradation of 1,2‐dichloropropane (1,2‐DCP) and 1,1‐dichlorethane (1,1‐DCA) was observed in the anaerobic microcosms, but nutrient addition enhanced their degradation in the aerobic biotic microcosms. The aerobic degradation half‐lives for 1,2‐DCP and 1,1‐DCA were 63 and 56 days, respectively. Evaluation of in situ chemical oxidation (ISCO) demonstrated that chelate‐modified Fenton's reagent was effective in degrading aqueous‐phase PCE, TCE, 1,1,1‐TCA, 1,2‐DCP, etc.; however, this approach had minimal effects on solid‐phase contaminants. The observed oxidant demand was 16 g‐H₂O₂/L‐groundwater. The oxidation reaction rates were not highly sensitive to the molar ratio of H₂O₂:Fe²⁺:citrate. A ratio of 60:1:1 resulted in slightly faster removal of chemicals of concern (COCs) than those of 12:1:1 and 300:1:1. This treatment resulted in increases in dissolved metals (Ca, Cr, Mg, K, and Mn) and a minor increase of vinyl chloride. Treatment with zero‐valent iron (ZVI) resulted in complete dechlorination of PCE, and TCE to ethene and ethane. ZVI treatment reduced 1,1,1‐TCA only to 1,1‐DCA and chloroethane (CA) but had little effect on reducing the levels of 1,2‐DCP, 1,1‐DCA, and CA. The longevity test showed that one gram of 325‐mesh iron powder was exhausted in reaction with > 22 mL of groundwater. The short life of ZVI may be a barrier to implementation. The ZVI surface reaction rates (k_sa) were 1.2 × 10^?2 Lm^?2h^?1, 2 × 10^?3 Lm^?2h^?1, and 1.2 × 10^?3 Lm^?2h^?1 for 1,1,1‐TCA, TCE, and PCE, respectively. Based upon the results of this study, in situ bioremediation appeared to be more suitable than ISCO and ZVI for effectively treating the groundwater contamination at the site. © 2004 Wiley Periodicals, Inc.     

Lysinibacillus sphaericus and Geobacillus sp Biodegradation of Petroleum Hydrocarbons and Biosurfactant Production

Petroleum oil is a major driver of worldwide economic activity, but it has also created contamination problems during the storage and refining process. Also, unconventional resources are natural resources, which require greater than industry‐standard levels of technology or investment to exploit. In the case of unconventional hydrocarbon resources, additional technology, energy, and capital have to be applied to extract the gas or oil. Bioremediation of petroleum spill is considered of great importance due to the contaminating effects on human health and the environment. For this reason, it is important to reduce total petroleum hydrocarbons (TPH) in contaminated soil. In addition, biosurfactant production is a desirable property of hydrocarbon‐degrading microorganisms. Seven strains belonging to Lysinibacillus sphaericus and Geobacillus sp were selected to evaluate their ability to biodegrade TPH in the presence of toxic metals, their potential to produce biosurfactants, and their ability to improve the biodegradation rate. The seven bacterial strains examined in this study were able to utilize crude petroleum‐oil hydrocarbons as the sole source of carbon and energy. In addition, their ability to degrade crude oil was not affected by the presence of toxic metals such as chromium and arsenic. At the same time, the strains were able to reduce toxic metals concentration through biosorption processes. Biosurfactant production was determined using the drop‐collapsed method for all strains, and they were characterized as both anionic and cationic biosurfactants. Biosurfactants showed an increase in biodegradation efficiency both in liquid minimal salt medium and landfarming treatments. The final results in field tests showed an efficiency of 93 percent reduction in crude oil concentration by the selected consortium compared to soil without consortium. The authors propose L. sphaericus and Geobacillus sp consortium as an optimum treatment for contaminated soils. In addition, production of biosurfactants could have an application in the extraction of crude oil from unconventional hydrocarbon resources. © 2014 Wiley Periodicals, Inc.     

Effective bioremoval of Fe(III) ions using paprika (Capsicum annuum L.) pomace generated in the food industry

In these studies, removal of Fe(III) ions by biosorption processes from aqueous solutions was carried out using paprika (Capsicum annuum L.) pomace generated during processing in the food industry. The biosorbent material was characterized using several analytical methods, including particle size distribution, XRD, SEM–EDS, electrokinetic zeta potential, surface area analysis (BET, BJH), thermogravimetry, morphology (SEM), spectrophotometry FT-IR. Several factors, such as biosorbent dosage, initial concentration, contact time and initial pH were analyzed to show an effect on the bioremoval process, efficiency and adsorption capacity. As a result, the maximum adsorption efficiency and capacity were determined to be 99.1% and 7.92 mg/g, respectively. Based on the kinetics analysis, the bioremoval process is better described by the Langmuir isotherm model and the pseudo-second order equation model. In conclusion, the achieved research results suggest that paprika biomass can be an effective material for efficiently removing iron(III) from wastewater and improving water quality. These studies on the recovery of iron metal from the environment fit in the latest trends in the concept of the global circular economy.

     

Influence of groundwater conditions and co‐contaminants on sorption of perfluoroalkyl compounds on granular activated carbon

Per and polyfluoroalkyl substances (PFAS) are emerging and persistent organic pollutants that have been detected in many environmental media, humans, and wildlife. A common method to effectively remove PFAS from water is adsorption by activated carbon. Preliminary sorption experiments were conducted using five characterized Calgon Corporation coal‐based granular activated carbon (GAC; F100, F200, F816, F300, and F400), one coconut‐based GAC (CBC‐OLC 12 × 30), and one Jacobi Corporation coal‐based GAC (Omni‐G 12 × 40). Sorption of four representative PFAS onto each GAC was measured to select the most favorable carbon sources. F400 and CBC were chosen based on their performance in preliminary PFAS sorption experiments and contrasting properties. Freundlich and Langmuir isotherm models were developed for perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonate (PFOS) at an initial concentration of 1 mg/L. Sorption capacities were determined for PFOA and PFOS individually and in the mixture. Individual compounds showed higher sorption than when present in the mixture for both PFOA and PFOS. PFOS showed higher sorption than PFOA both individually and in the mixture and F400 showed higher sorption capacity than CBC. The presence of co‐contaminants (kerosene, trichloroethylene, and ethanol), and variations in groundwater conditions (pH, presence of anions, naturally occurring organic matter, and iron oxides) demonstrated limited impact on the sorption of PFAS onto GAC under the experimental conditions tested.     

Complete Degradation of Hexahydro‐1,3,5‐Trinitro‐1,3,5‐Triazine (RDX) by a Co‐Culture of Gordonia sp. KTR9 and Methylobacterium sp. JS178

The presence of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) in soil and groundwater is a major contamination issue at many military facilities around the world. Gordonia sp. KTR9 metabolizes RDX as a nitrogen source for growth producing 4‐nitro‐2,4‐diazabutanal (NDAB) as a dead‐end product. Methylobacterium sp. strain JS178 degrades NDAB as a sole source of nitrogen for growth. A mixed culture of strains KTR9 and JS178 was able to completely degrade RDX. There was no difference in rate of RDX degradation by KTR9 alone or in co‐culture with JS178. The first‐order degradation coefficients of RDX and NDAB in the co‐culture were 0.08 hr^?1 and 0.002 hr^?1, respectively. In the co‐culture that initially contained RDX plus NDAB, strain JS178 degraded the NDAB that was produced by KTR9 as shown by a decrease in the molar yield of NDAB (from RDX) from 1.0 to –0.11. Co‐cultures of strains KTR9 and JS178 could be used to promote complete degradation of RDX in soils or groundwater. ©2016 Wiley Periodicals, Inc.     

Enzyme-Assisted Extraction and Pb<Superscript>2+</Superscript> Biosorption of Polysaccharide from <Emphasis Type="Italic">Cordyceps militaris</Emphasis>

The enzyme assisted extraction conditions of polysaccharide from Cordyceps militaris mycelia were firstly investigated by kinetics analysis and the optimal operating was found to be: extraction temperature 40 °C; solid-solvent ratio 1:20; extraction pH 4.0; cellulase concentration 2.0%. The polysaccharide extraction yield was 5.99% under these optimized conditions. Furthermore, a fundamental investigation of the biosorption of Pb²⁺ from aqueous solution by the C. militaris polysaccharide was performed under batch conditions. The suitable pH (5.0), polysaccharide concentration (0.20 g L^?1), initial Pb²⁺ concentration (300 mg L^?1) and contact time (40 min) were outlined to enhance Pb²⁺ biosorption from aqueous medium. The Langmuir isotherm model and pseudo first order kinetic model fitted well to the data of Pb²⁺ biosorption, suggesting the biosorption of Pb²⁺ onto C. militaris polysaccharide was monolayer biosorption and physical adsorption might be the rate-limiting step that controlled the adsorption process. FTIR analysis showed that the main functional groups of C. militaris polysaccharide involved in adsorption process were carbonyl, carboxyl, and hydroxyl groups.     

Field‐scale uranium (VI) bioimmobilization monitored by lipid biomarkers and 13C‐acetate incorporation

At the Old Rifle uranium mill‐tailing site in eastern Colorado, a test of subsurface amendment with acetate to stimulate the reductive immobilization of uranium was monitored by using lipid biomarker analysis and incorporation of ¹³C‐labeled acetate into lipid biomarkers. Both sediment and groundwater samples were analyzed. Within 7 days of acetate addition, groundwater microbial biomass increased by a factor of 5, and remained higher than control values in most samples for the 28 days sampled. At 29 days after the beginning of acetate amendment, 4 of 12 sediment samples had microbial biomass greater than the 95 percent confidence interval of controls. The mole percents of the phospholipid fatty acids 16:1ω7c and 16:1ω5c increased over control values upon acetate amendment, and incorporated high levels of ¹³C from labeled acetate in groundwater and sediment samples. 16:1ω7c is a biomarker for Geobacter, and evidence is provided that 16:1ω5c represents an unidentified iron‐reducing bacterium, probably a member of the Desulfobulbaceae. Biomarkers for organisms other than iron‐reducing bacteria, iso‐ and anteiso‐branched fatty acids and 18:1ω9c, decreased upon acetate amendment, and had their highest stable isotope incorporation at least 4 days after labeled acetate amendment ended, evidence for carbon‐sharing between iron‐reducers and other microorganisms. © 2011 Wiley Periodicals, Inc.     

Eco-Friendly, Vascular Shape and Interpenetrating Poly (Acrylic Acid) Grafted Pectin Hydrogels; Biosorption and Desorption Investigations

The synthesis and characterization of poly (acrylic acid) grafted pectin hydrogel followed by biosorption and desorption characteristics of cadmium, as a model heavy metal, have been studied. The grafted eco-friendly pectin based interpenetrating hydrogel was prepared in the presence of gluteraldehyde crosslinker under N₂ atmosphere and characterized using ¹H-NMR, FTIR, TGA and SEM techniques. Gluteraldehyde was found to form one-arm and two-arm crosslinks in the copolymer. Upon grafting, two-dimensional sheet structures bounded to tubular and vascular cylindrical rods were observed. The biosorption and desorption data, determined experimentally, were fitted to pseudo-second order reaction kinetics. At higher ionic strength values, the maximum metal uptake value (q _max) was lowered and pseudo-second order rate constant (k ₂) was increased. Whereas, at higher pH values the maximum metal uptake value (q _max) was increased and Pseudo-second order rate constant (k ₂) was decreased. 0.1?M HCl solution was a suitable eluent to regenerate the hydrogel surface and recover the adsorbed cadmium metal ions. Pectin based copolymer could be used as an efficient candidature biosorbent for the recovery of cadmium metal ions from aqueous solutions.     

Estimation of transport parameters of phenolic compounds and inorganic contaminants through composite landfill liners using one-dimensional mass transport model

One-dimensional (1D) advection–dispersion transport modeling was conducted as a conceptual approach for the estimation of the transport parameters of fourteen different phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and three different inorganic contaminants (Cu, Zn, Fe) migrating downward through the several liner systems. Four identical pilot-scale landfill reactors (0.25 m³) with different composite liners (R1: 0.10 + 0.10 m of compacted clay liner (CCL), L_e = 0.20 m, k_e = 1 × 10⁻⁸ m/s, R2: 0.002-m-thick damaged high-density polyethylene (HDPE) geomembrane overlying 0.10 + 0.10 m of CCL, L_e = 0.20 m, k_e = 1 × 10⁻⁸ m/s, R3: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick bentonite layer encapsulated between 0.10 + 0.10 m CCL, L_e = 0.22 m, k_e = 1 × 10⁻⁸ m/s, R4: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick zeolite layer encapsulated between 0.10 + 0.10 m CCL, L_e = 0.22 m, k_e = 4.24 × 10⁻⁷ m/s) were simultaneously run for a period of about 540 days to investigate the nature of diffusive and advective transport of the selected organic and inorganic contaminants. The results of 1D transport model showed that the highest molecular diffusion coefficients, ranging from 4.77 × 10⁻¹⁰ to 10.67 × 10⁻¹⁰ m²/s, were estimated for phenol (R4), 2-MP (R1), 2,4-DNP (R2), 2,4-DCP (R1), 2,6-DCP (R2), 2,4,5-TCP (R2) and 2,3,4,6-TeCP (R1). For all reactors, dispersion coefficients of Cu, ranging from 3.47 × 10⁻⁶ m²/s to 5.37 × 10⁻² m²/s, was determined to be higher than others obtained for Zn and Fe. Average molecular diffusion coefficients of phenolic compounds were estimated to be about 5.64 × 10⁻¹⁰ m²/s, 5.37 × 10⁻¹⁰ m²/s, 2.69 × 10⁻¹⁰ m²/s and 3.29 × 10⁻¹⁰ m²/s for R1, R2, R3 and R4 systems, respectively. The findings of this study clearly indicated that about 35–50% of transport of phenolic compounds to the groundwater is believed to be prevented with the use of zeolite and bentonite materials in landfill liner systems.     

Graft Copolymerization of Methyl Acrylate onto Cellulosic Biofibers: Synthesis,Characterization and Applications

Graft copolymerization of cellulosic biopolymers with synthetic polymers is of enormous interest because of its application in biofiltration, biosorption, biomedical, biocomposites and various other eco-friendly materials. Synthesis of graft copolymers of methyl acrylate onto mercerized Grewia optiva biofibers using ferrous ammonium sulfate–potassium per sulfate as redox initiator in air was carried out. Different reaction parameters such as amount of solvent, monomer concentration, initiator molar ratio, reaction time and reaction temperature were optimized to get the maximum percentage of grafting. The graft copolymers thus formed were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis and differential thermogravimetric techniques. A plausible mechanism for explanation of the graft copolymerization reactions pattern shown is offered. The effect of grafting percentage on the physico–chemical properties of raw as well as grafted Grewia optiva biofibers has also been investigated. The graft copolymers have been found to be more moisture resistant and also showed better chemical and thermal resistance. Green polymer composites were also successfully prepared through compression molding technique by using grafted Grewia optiva biofibers as reinforcement.     

Effect of chelating agents in phytoremediation of heavy metals

Chelate‐assisted metal uptake by plants has only recently been discovered in the remediation industry. The simultaneous accumulation of lead, arsenic, copper, and cadmium in plants after application of chelating agents to soil is a promising technology enhancement for phytoremediation. One of the most powerful and commonly used chelating agents is ethylene diamine tetra acetic acid (EDTA), which forms complexes with many of the metal contaminants within the natural environment. This study was conducted to determine the efficiency of an emergent wetland plant species Typha sp. and floating wetland macrophytes such as Pistia sp., Azolla sp., Lemna sp., Salvinia sp., and Eichhornia sp. in phytoremediation of various heavy metals with addition of a chelating agent such as EDTA. EDTA addition to the treatment systems increased the uptake of heavy metals by plants, which was much pronounced with lead and copper. However, the pattern of uptake by plants was similar as that of heavy metals without EDTA amendments. © 2012 Wiley Periodicals, Inc.     

Biodegradation of Aliphatic and Aromatic Hydrocarbons: Specificity among Bacteria Isolated from Refinery Waste Sludge

Indigenous microorganisms, enriched and isolated from refinery waste sludge, were observed to possess a broad range of metabolic activities for mixtures of several classes of substrates of petroleum hydrocarbons, such as monoaromatic and polycyclic aromatic hydrocarbons (PAHs) and n- and branched alkanes. Three of the best-growing bacterial isolates selectively enriched with these compounds were identified by 16S rDNA sequencing as belonging to the genera Enterobacter and Ochrobactrum. Two of them, Enterobacter sp. strain EK3.1 and Ochrobactrum sp. strain EK6 utilise a hydrocarbon mixture of the branched alkane 2,6,10,14-tetramethylpentadecane and the PAHs acenaphthylene and acenaphthene. Enterobacter sp. strain EK4 can grow with a mixture of 2,6,10,14-tetramethylpentadecane, toluene, acenaphthylene and acenaphthene as carbon sources. Nucleic acid fingerprint analysis, by terminal restriction fragment length polymorphism (T-RFLP) of the PCR-amplified 16S rRNA genes, of the autochthonous bacterial community in contaminated soil samples showed complex and different community structures under different treatments of refinery waste sludge in landfarm areas. The characteristic peaks of the T-RFLP profiles of the individual, isolated degrading bacteria Enterobacter spp. and Ochrobactrum sp. were detected in the T-RFLP fingerprint of the bacterial community of the four months old treated landfarm soil, suggesting the enrichment of bacteria belonging to the same operational taxonomic units, as well as their importance in degrading activity.