Silver nanoparticles (Ag-NPs) readily transform in the environment, which modifies their properties and alters their transport, fate, and toxicity. It is essential to consider such transformations when assessing the potential environmental impact of Ag-NPs. This review discusses the major transformation processes of Ag-NPs in various aqueous environments, particularly transformations of the metallic Ag cores caused by reactions with (in)organic ligands, and the effects of such transformations on physical and chemical stability and toxicity. Thermodynamic arguments are used to predict what forms of oxidized silver will predominate in various environmental scenarios. Silver binds strongly to sulfur (both organic and inorganic) in natural systems (fresh and sea waters) as well as in wastewater treatment plants, where most Ag-NPs are expected to be concentrated and then released. Sulfidation of Ag-NPs results in a significant decrease in their toxicity due to the lower solubility of silver sulfide, potentiall...

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Environmental transformations of silver nanoparticles: impact on stability and toxicity.

: Ecological and toxicological aspects of silver (Ag) and silver salts in the environment are briefly summarized with an emphasis on natural resources. Elevated silver concentrations in biota occur in the vicinities of sewage outfalls, electroplating plants, mine waste sites, and silver-iodide seeded areas; in the United States, the photography industry is the major source of anthropogenic silver discharges into the biosphere. Silver and its compounds are not known to be mutagenic, teratogenic, or carcinogenic. Under normal routes of exposure, silver does not pose serious environmental health problems to humans at less than 50 ug total Ag/L drinking water or 10 ug total Ag/m3 air. Free silver ion, however, was lethal to representative species of sensitive aquatic plants, invertebrates, and teleosts at nominal water concentrations of 1.2 to 4.9 ug/L; sublethal effects were significant between 0.17 and 0.6 ug/L. Silver was harmful to poultry at concentrations as low as 1.8 mg total Ag/kg whole egg fresh weight by way of injection, 100 mg total Ag/L in drinking water, or 200 mg total Ag/kg in diets; sensitive mammals were adversely affected at total silver concentrations as low as 250 ug/L in drinking water, 6 mg/kg in diets, or 13.9 mg/kg whole body.

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Silver Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review

The disclosed invention relates to a process for making a multiphase mixture, comprising: flowing a first fluid stream through a process microchannel, the first fluid stream comprising at least one liquid and/or at least one gas, the process microchannel having an apertured section; flowing a second fluid stream through the apertured section into the process microchannel in contact with the first fluid stream to form the multiphase mixture, the second fluid stream comprising at least one gas and/or at least one microbody-forming material, the first fluid stream forming a continuous phase in the multiphase mixture, the second fluid stream forming a discontinuous phase dispersed in the continuous phase.

Multiphase mixing process using microchannel process technology

The present invention relates to a method for treating waste water including the steps of: oxidizing the waste water, and then treating the oxidized waste water with a reverse osmosis membrane having high salt rejection rate. By being treated with the reverse osmosis membrane, the waste water is separated into a impermeated liquid which contains a oxidizable substance, and a permeated liquid which contains almost no oxidizable substance.

Method for treating waste water

The present invention relates to a catalyst for wastewater treatment and a method for wet oxidation treatment of wastewater using the catalyst, in particular, the catalyst of the present invention can suitably be used in wet oxidation treatment of wastewater, under high temperature and high pressure conditions. The present invention provides a catalyst for wastewater treatment containing a catalytic active constituent containing at least one kind of an element selected from the group consisting of manganese, cobalt, nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium, or a compound thereof, and a carrier constituent containing at least one kind of an element selected from the group consisting of iron, titanium, silicon, aluminum and zirconium, or a compound thereof, characterized in that solid acid amount of the carrier constituent is equal to or more than 0.20 mmol/g.

Catalyst for wastewater treatment and method for wastewater treatment using said catalyst

This invention discloses a method for oxidizing and/or decomposing organic and/or inorganic oxidizable substances in waste water by wet oxidation with a use of a catalyst, wherein the oxidizable substances are oxidized and/or decomposed with an oxygen containing gas in the presence of the catalyst under pressure such that said waste water retains the liquid phase thereof at temperature of 50 to less than 170° C.; the catalyst contains activated carbon; and controlling an oxygen concentration in an exhaust gas in the range from 0 to 5 vol %. The present inventive method is capable of treating waste water efficiently for a long period in a stable manner at the reduced temperatures and as compared with the substantially higher temperatures and pressures used in many of the prior art method.

Catalyst for treating waste water, method for preparing the same and process for treating waste water

A process for purifying a photographic waste solution is disclosed. The photographic waste solution is purified by successively performing: noncatalytic wet oxidation at a temperature of from 140°C up to 370°C under such a pressure as to hold said waste solution in a liquid phase while supplying an oxygen-containing gas thereto; solid-liquid separation of the solid matters and/or suspended matters thus formed; catalytic wet oxidation at a temperature of from 140°C up to 370°C under such a pressure as to hold said waste solution in a liquid phase while supplying an oxygen-containing gas thereto; and a biological treatment comprising a combination of an aerobic biological treatment with an anaerobic biological treatment.

Process for treating photographic waste solution

PROBLEM TO BE SOLVED: To generate a good gas-liquid distribution state at a superficial inlet or a filler inlet of a catalyst or the like by eliminating pulsating flow or deflection in a gas-liquid dispersion apparatus, a gas-liquid contact apparatus and a waste water treatment apparatus. SOLUTION: In a gas-liquid dispersion apparatus arranged in a system wherein a liquid forms a continuous phase to flow and gas flows upwardly, two or more partition members are arranged at a predetermined interval so as to cut off a gas-liquid passage wherein a gas-liquid mixed phase state is formed. Each of the partition members is selected from a single ported plate 1 equipped with a single through hole, a perforated plate 2 equipped with a plurality of through holes, a single ported plate 3 fitted with a collision plate wherein the collision plate is fitted in the vicinity of the outlet side of the through hole of the single ported plate and a perforated plate 4 fitted with a collision plate wherein the collision plate is fitted in the vicinity of the outlet side of the through holes of the perforated plate 1.

Gas-liquid dispersion apparatus, gas-liquid contact apparatus and waste water treatment apparatus

PROBLEM TO BE SOLVED: To prevent uneven current flow of gas and supply homogeneous gas- liquid fluid state by arranging a porous plate in such a manner that a gas-liquid flow passage in which a gas-liquid mixed phase state is formed, is shut off and extending a liquid passage consisting of a partitioned passage toward the inlet side of a gas flow passage from the porous plate. SOLUTION: A porous plate 10 is disposed in such a manner that the plate 10 shuts off a gas-liquid flow passage and holes h1 -h11 are formed in the porous plate 10. In addition, a liquid pipe 10a is installed projecting as a liquid passage toward the inlet side of a gas passage on the peripheral edges of specific holes h2 , h5 , h7 , h10 . Further, this gas-liquid dispersion device A with a liquid passage allows a liquid to pass through the through holes h2 , h5 , h7 , h10 of the liquid pipe 10 and a gas to pass through the other hole, if this device A is, for example, used as a gas-liquid contact device of a bubbling tower type. In this case, the gas passage inlet part of the gas-liquid dispersion device A acts as a gas storage part by the formation of a gas phase having a function as a buffer part to suppress a pulsating flow with the gas and the liquid, so that the gas and the liquid which are free from the pulsating flow are uniformly dispersed.

Gas/liquid dispersion device, gas/liquid contact device and waste water treating device

PROBLEM TO BE SOLVED: To produce a catalyst that can stably exhibit excellent catalytic activity for a long term when used in the wet oxidation treatment of wastewater and to provide a method for treating wastewater by using the catalyst SOLUTION: There are provided a catalyst prepared by allowing a support to carry an active component, wherein the active component is at least one element selected from the group consisting of manganese, iron, cobalt, nickel, cerium, chromium, praseodymium, copper, silver, gold, platinum, palladium, rhodium, and iridium or a compound containing at least one of these elements, and at least 70%, based on the entire active component, active component is present within the distance of 500 μm from the surface of the support when detected with an X-ray analyzer along an arbitrary axis in any arbitrary cross section of the support

Shioda Yusuke

Papers

Catalyst for treating waste water, method for preparing the same and process for treating waste water

Process for treating photographic waste solution

Gas-liquid dispersion apparatus, gas-liquid contact apparatus and waste water treatment apparatus

Gas/liquid dispersion device, gas/liquid contact device and waste water treating device

Wastewater treatment catalyst and method for treating wastewater by using the catalyst