Sorption of Cr(III) and Cr(VI) to High and Low Pressure Synthetic Nano-Magnetite (Fe3O4)Particles

The binding of Cr(III) and Cr(VI) to synthetic nano-magnetie particles synthesized under open vessel conditions and a microwave assisted hydrothermal synthesis techniques was investigated. Batch studies showed that the binding of both the Cr(III) and Cr(VI) bound to the nano-materials in a pH dependent manner. The Cr(III) maximized at binding at pH 4 and 100% binding. Similarly, the Cr(VI) ions showed a maximum binding of 100% at pH 4. The data from the time dependency studies showed for the most part the majority of the binding occurred within the first 5 minutes of contact with the nanomaterial and remained constant thereafter. In addition, the effects of the possible interferences were investigated which showed some effects on the binding of both Cr(III) and Cr(VI). However, the interferences never completely eliminated the chromium binding. Isotherm studies conducted at room temperature showed the microwave synthesized nanomaterials had a binding capacity of 1208 ± 43.9 mg/g and 555 ± 10.5 mg/g for Cr(VI) and Cr(III), respectively. However, the microwave assisted synthesized nanomaterials had capacities of 1705 ± 14.5 and 555± 10.5 mg/g for Cr(VI) and Cr(III), respectively. XANES studies showed the Cr(VI) was reduced to Cr(III), and the Cr(III) remained as Cr(III). In addition, the XANES studies indicated that the chromium remained coordinated in an octahedral arrangement of oxygen atoms

Growth, Gas Exchange, and Mineral Nutrients of Ornamental Grasses Irrigated with Saline Water

Ornamental grasses are commonly used in urban landscapes in Utah and the Intermountain West of the United States. The relative salt tolerance of Eragrostis spectabilis (Pursh) Steud. (purple love grass), Miscanthus sinensis Andersson ‘Gracillimus’ (maiden grass), Panicum virgatum L. ‘Northwind’ (switchgrass), and Schizachyrium scoparium (Michx.) Nash (little bluestem) were evaluated in a greenhouse. Plants were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m–1 (control), or saline solution at an EC of 5.0 or 10.0 dS·m–1. At harvest (65 days after the initiation of treatment), P. virgatum and S. scoparium exhibited no foliar salt damage, and E. spectabilis and M. sinensis had minimal foliar salt damage when irrigated with saline solution at an EC of 5.0 dS·m–1. At an EC of 10.0 dS·m–1, P. virgatum and S. scoparium still had no foliar salt damage, but E. spectabilis and M. sinensis displayed slight foliar salt damage, with visual scores greater than 3 (0 = dead; 5 = excellent). Compared with the control, saline solution at an EC of 5.0 and 10.0 dS·m–1 reduced the shoot dry weight of all ornamental grasses by 25% and 46%, respectively. The leaf sodium (Na+) concentration of E. spectabilis, M. sinensis, P. virgatum, and S. scoparium irrigated with saline solution at an EC of 10.0 dS·m–1 increased 14.3, 52.6, 5.3, and 1.7 times, respectively, and the chloride (Cl–) concentration increased by 9.4, 11.1, 2.8, and 2.7 times, respectively. As a result of the salt-induced water deficit, plant height, leaf area, number of inflorescences and tillers, net photosynthesis rate (Pn), stomatal conductance (gS), and transpiration rate of four tested ornamental grasses decreased to some extent. Although high Na+ and Cl– accumulated in the leaf tissue, all ornamental grass species still had a good visual quality, with average visual scores greater than 3. In conclusion, all ornamental grasses showed a very strong tolerance to the salinity levels used in this research

Adsorption of Toxic Metal Ions From Solution by Inactivated Cells of Larrea Tridentata Creosote Bush

Larrea tridentata (creosote bush) is a plant that grows abundantly in the desert environment. This desert plant has been found naturally growing in heavy-metal contaminated soils. Previous experiments showed that the inactivated biomass of creosote bush was able to adsorb Cu(II) ions from aqueous solutions. The copper-binding capacity of the bush biomass that grows in heavy-metal uncontaminated soils was higher than the biomass that grows in heavy-metal contaminated soils. Experiments were performed to determine the ability of creosote bush biomass (grown in heavy metal uncontaminated soils) to adsorb Pb(II), Cd(II), Zn(II), Cr(III), Cr(VI), and Ni(II) ions from aqueous solutions. Batch pH profile experiments for these metal ions showed that the metal ion binding was different for every metal tested but increased as the pH was raised from 2.0 to 6.0. The metal ion uptake by the roots, stems, and leaves was quite fast. Binding capacity experiments showed a more significant binding capacity for lead(II) and chromium(III) ions and in general, the leaves bound more metal ions than the stems and roots. A great portion of the metal ions adsorbed by the creosote’s roots, stems, and leaves was desorbed by treatment with 0.1 M HCl (up to 99% in some cases). Biomass of creosote bush may prove to be useful to remove and recover metal ions from contaminated waters

Flow Rate and Interference Studies for Copper Binding to a Silica-Immobilized Humin Polymer Matrix: Column and Batch Experiments

Batch and column experiments were performed to determine the Cu(II) binding capacity of silica-immobilized humin biomass. For column studies, 500 bed volumes of a 0.1 mM Cu(II) solution were passed through humin packed columns at the flow rates of 1, 1.5, 2, and 3 mL/min. The biopolymer showed an average Cu binding capacity of 12 ± 1.5 mg/g and a Cu recovery of about 96.5 % ± 1.5. The breakthrough points for Cu(II) alone were approximately 420, 390, 385, and 300 bed volumes for the flow rates of 1, 1.5, 2 and 3 mL/min, respectively. The interference studies demonstrated that at low concentrations, the hard cations Ca(II) and Mg(II) did not seem to represent a major interference on Cu(II) binding to the humin biopolymer. The selectivity showed by this biopolymer was Cu(II)>Ca(II)>Mg(II). On the other hand, batch experiments showed that Ca(II) + Mg(II) at 100mM each reduced the Cu(II) binding to 73 %. However, 1000 mM concentrations of Ca(II) and Mg(II), separately and in mixture, reduced the Cu(II) binding to 47 %, 44 % and 31 %, respectively. The results of this study showed that immobilized humin in a silica matrix could represent an inexpensive bio-source for Cu removal from contaminated water, even in the presence of low concentrations of the hard cations Ca(II) and Mg(II)

Ability of Immobilized Cyanobacteria to Remove Metal Ions From Solution and Demonstration of the Presence of Metallothionein Genes in Various Strains

Synechococcus sp. PCC 7942 has the ability to grow in mass quantity under ideal conditions; such an ability provides usable biomass at a minimal effort. Using lyophilized biomass grown under normal conditions, Synechococcus was tested for its potential to bind metal ions from solution. Batch experiments have determined the optimum binding pH, time dependency, and metal binding capacities for copper(II), lead(II), nickel(II), cadmium(II), chromium(III), and chromium(VI), along with desorption of the metal bound. The biomass studied showed an affinity for five of the metal ions, with an optimum binding at pH 5. Time dependency studies showed that this cyanobacterium had rapid binding, while capacity experiments showed this cyanobacterial strain to bind 11.3 mg of copper(II) per gram of biomass, 30.4mg of lead(II) per gram of biomass, 3.2 mg of nickel(II) per gram of biomass, 7.2 mg of cadmium (II) per gram of biomass, and 5.4 mg of chromium (III) per gram of biomass. More than 98% of copper(II), lead(II), and nickel(II) metal ions were recovered, while over 50 % of cadmium(II) and chromium(III) were recovered when treated with 0.1M HCl. The biomass was immobilized in a silica polymer and tested for its binding ability under flow conditions. Using 0.1mM concentrations of the previously indicated metals, individual experimental results showed an average of 143 mg/L copper(II), 1456 mg/L lead(II), 142 mg/L nickel(II), and 529 mg/L cadmium(II) bound by the immobilized biomass. Treatment with 0.2M HCl resulted in nearly 100% recovery for both copper(II) and lead(II) from the column, 79% recovery of cadmium(II), while recovery for nickel(II) was 42%. Experiments were conducted to determine if many cycles of metal binding- stripping by the immobilized biomass were possible. Further, attempts were made to demonstrate the presence of metallothioneins in various strains of cyanobacteria which may serve as defense mechanisms against metal ion toxicity. Such proteins may be used to develop engineered strains of cyanobacteria with increased metal ion binding ability. Synechococcus can eventually be used as a source for a novel approach in using biosystems to remediate contaminants from solution and making those contaminants available to industry through an environmentally friendly biofiltration system

Binding of Silver(I) Ions by Alfalfa Biomass (Medicago Sativa): Batch PH, Time, Temperature, and Ionic Strength Studies

In this study, the use of alfalfa biomass as a cost-effective and environmentally safe technique to recover Ag(I) ions from aqueous solutions is reported. This investigation consisted of batch pH profile, time, temperature, and ionic strength dependence studies. Results showed that alfalfa biomass presented the highest adsorption of Ag(I) ions in the pH range of 7 to 9 with a maximum adsorption capacity of 27.37 mg Ag•g-1 of dry biomass, evaluated with a solution of 32.4 ppm of Ag(I). Time and temperature studies demonstrated a stable adsorption of Ag(I) ions by the biomass during the first hour of exposure, with a small decrease in adsorption after this period. Temperature experiments showed that Ag(I) adsorption decreases significantly at 50 ºC as compared to 4ºC and 24 ºC. However, the differences between 4ºC and 24ºC are small. Ionic strength experiments showed that interfering ions (Na and Ca) reduce the adsorption capacity of the biomass. Results of this investigation showed that alfalfa biomass can be effectively used in the recovery process of silver ions from aqueous solutions

Sorption kinetic study of selenite and selenate onto a high and low pressure aged iron oxide nanomaterial

The sorption of selenite (SeO32−) and selenate (SeO42−) onto Fe3O4 nanomaterials produced by non microwave-assisted or microwave-assisted synthetic techniques was investigated through use of the batch technique. The phase of both synthetic nanomaterials was determined to be magnetite by X-ray diffraction. The average grain sizes of non microwave-assisted and microwave-assisted synthetic Fe3O4 were determined to be 27 and 25 nm, respectively through use of the Scherrer\u27s equation. Sorption of selenite was pH independent in the pH range of 2-6, while sorption of selenate decreased at pH 5 and 6. The addition of Cl− had no significant effect on selenite or selenate binding, while the addition of NO3− only affected selenate binding to the microwave assisted Fe3O4. A decrease of selenate binding to both synthetic particles was observed after the addition of SO42− while selenite binding was not affected. The addition of PO43− beginning at concentrations of 0.1 ppm had the most prominent effect on the binding of both selenite and selenate. The capacities of binding, determined through the use of Langmuir isotherm, were found to be 1923 and 1428 mg Se/kg of non microwave-assisted Fe3O4 and 2380 and 2369 mg Se/kg of microwave-assisted Fe3O4 for selenite and selenate, respectively

Gold Binding by Native and Chemically Modified Hops Biomasses

Heavy metals from mining, smelting operations and other industrial processing facilities pollute wastewaters worldwide. Extraction of metals from industrial effluents has been widely studied due to the economic advantages and the relative ease of technical implementation. Consequently, the search for new and improved methodologies for the recovery of gold has increased. In this particular research, the use of cone hops biomass (Humulus lupulus) was investigated as a new option for gold recovery. The results showed that the gold binding to native hops biomass was pH dependent from pH 2 to pH 6, with a maximum percentage binding at pH 3. Time dependency studies demonstrated that Au(III) binding to native and modified cone hops biomasses was found to be time independent at pH 2 while at pH 5, it was time dependent. Capacity experiments demonstrated that at pH 2, esterified hops biomass bound 33.4 mg Au/g of biomass, while native and hydrolyzed hops biomasses bound 28.2 and 12.0 mg Au/g of biomass, respectively. However, at pH 5 the binding capacities were 38.9, 37.8 and 11.4 mg of Au per gram of native, esterified and hydrolyzed hops biomasses, respectively