Efficient Removal of Nitrate in Neutral Solution Using Zero-Valent Al Activated by Soaking.

Nitrate is a contaminant widely found in surface water, and a high concentration of nitrate can pose a serious threat to human health. Zero-valent iron is widely used to reduce nitrate in aqueous solution, but an acidic condition is required. Zero-valent aluminum has a much lower redox potential ((Al/Al) = -1.

Separation of Excess Fluoride from Water Using Amorphous and Crystalline AlOOH Adsorbents.

Aluminum hydroxide is an effective defluoridation adsorbent; however, the poor defluoridation performance limits its wide application. In this work, amorphous and crystalline AlOOH adsorbents are synthesized through hydrolysis of Al salts, and their defluoridation performances are evaluated in terms of adsorption capacity and rate, sensitivity to pH value, and water quality after defluoridation. The defluoridation performance of AlOOH is closely related to the hydrolysis pH value, but hardly to the type of Al salts.

A comparative study on high-efficient reduction of bromate in neutral solution using zero-valent Al treated by different procedures.

Bromate, a toxic by-product of bromide-containing drinking water after disinfecting with ozone, has attracted much attention in the past two decades. Traditional methods to activate zero-valent metals for reducing bromate are to eliminate their surface oxide layer by acid washing. In this work, for the first time, zero-valent Al (ZVAl) was surface treated by the following procedures including soaking, soaking and freeze-drying, soaking and heat-treating, and γ-AlO covering Al particle surfaces (GCAP).

Filtrates with Hydroxyl Radicals Prepared using Al + Acid + HO for Removing Organic Pollutants.

In this work, for the first time, high-activity filtrates were prepared by the reaction of aluminum (Al) powder with hydrogen peroxide (HO) in acidic solution and then filtration, which were used to degrade various organic pollutants such as phenol, methyl orange, and bisphenol A. It was found that the filtrates can effectively degrade and mineralize various organic pollutants and have a high efficiency comparable to their parent Al + acid + HO suspensions. The filtrates can keep their high activity for several weeks under ambient conditions, and the activity depends on their initial pH value.

Oxide modified aluminum for removal of methyl orange and methyl blue in aqueous solution.

In this work, pristine aluminum (Al) powder was soaked in deionized water for a time period and then it was dried and heat-treated at 400 °C such that a layer of fine AlO grains covered the Al particle surfaces, forming oxide modified Al powder (OM-Al). It was found that OM-Al greatly enhanced the efficiency in removing methyl orange (M-orange) and methyl blue (M-blue) in aqueous solution. The time to completely degrade M-orange and M-blue by OM-Al is about one third of that by pristine Al powder, and decreases with increasing dosage of OM-Al.

Relative Order of Acidity among Hydroxyl Groups of Oxyluciferin and Emission Light Colors in Aqueous Solution.

The magnitude of the acidity of the oxyluciferin in water in the ground and excited state is investigated, and it is found for the first time using computational approach that the enol group of the phenol-enol species is the most acidic in the ground state, but the deprotonation of the phenol of the phenol-keto form is the most favored in the excited state. The relative order of the acidity among the hydroxyl groups in the oxyluciferin is attributed to the sequence of the O-H bond lengths in the enol and phenol group of the phenol-enol form, and the phenol group of the phenol-keto species. The mechanism of determining the dominant emissive species in the excited state is proposed, and the dependence of emission light colors on the photoexcitation energy is elucidated by the high relative concentration of six chemical forms in the ground state and the absorption efficiency.

Arsenic removal from water by metal-organic framework MIL-88A microrods.

Fe-based metal-organic framework MIL-88A microrods were synthesized by hydrothermal method, which were used to adsorb As(V) in water for the first time. The experimental results indicated that MIL-88A has a very fast adsorption rate towards arsenic in water. The kinetic and isothermal data for arsenic removal were better fitted to the pseudo-second-order kinetic model and Langmuir model, respectively, implying a chemical and monolayer adsorption for As(V) on MIL-88A microrods.

Electrostatic Catalysis Induced by Luciferases in the Decomposition of the Firefly Dioxetanone and Its Analogue.

The variations of the barrier heights in the decomposition of the firefly dioxetanone and its analogues with the electrostatic field produced by the active site amino acid residues in the firefly luciferase are examined by a density functional theory study of the high-energy intermediates of the three luciferins. The positive electric field along the long-axis direction of the luciferins lowers the activation energy and acts as an electrostatic catalyst in the thermolysis process. The calculated barrier heights for the firefly dioxetanone and its analogues surrounded by the firefly Photinus pyralis luciferase show that the energy barrier of the firefly dioxetanone is lowered by the luciferase but is raised for the other analogue.

How Does the Local Electrostatic Field Influence Emitted Wavelengths and Bioluminescent Intensities of Modified Heteroaromatic Luciferins?

The firefly chromophore, oxyluciferin, is in the pocket of the firefly luciferase and is surrounded by the side-chains of some amino acid residues. The charged residues produce the local electrostatic field (LEF) around the oxyluciferin. The emitted wavelengths and intensities of the oxyluciferin and its heterocyclic analogs under the LEF are examined.