A composite comprising a hydroxyapatite and at least one additive which is present during hydroxyapatite synthesis. The additive may be embedded or incorporated into or coated onto the hydroxyapatite. The additive preferably increases the hydroxyapatite porosity, e.g., providing a higher pore volume and/or BET surface area than a hydroxyapatite material without additive. The additive preferably comprises an activated carbon, chitosan, hopcalite, clays, zeolites, sulfur, and/or a metal such as Al, Sn, Ti, Fe, Cu, Zn, Ni, Cu, Zr, La, Ce, in the form of metal, salt, oxide, oxyhydroxide, and/or hydroxide. The hydroxyapatite may be calcium-deficient. The composite is in the form of particles having a D50 of at least 20 m, a BET surface area of at least 120 m.sup.2/g; and/or a total pore volume of at least 0.3 cm.sup.3/g. An adsorbent material comprising a composite or a blend of composite with a hydroxyapatite without additive, and its use for removal of contaminants such as Hg, Se, As, and/or B from an effluent.

Techniques for removing sulfur compounds from a sulfur-containing gas stream can include contacting the gas with an absorption solution comprising a metal cation capable of reacting with the sulfur compound to form a metal sulphide precipitate and/or a metal mercaptide precipitate. In addition, the treatment can include controlling a concentration of the precipitates below a threshold to maintain rheological properties; subjecting the precipitate-enriched solution to vitalization; subjecting the precipitate-enriched solution to regeneration including oxidation; and/or other features to enhance the sulfur removal operations.

Disclosed herein are particulate sorbents, such as sorbents that can be used for mercury removal applications. The absorbent can comprise at least one ammonium phosphate and at least one activated carbon selected from unhalogenated activated carbon and halogenated activated carbon, wherein the halogenated activated carbon contains at least one halogen impregnant on its surface. Also disclosed are methods of making sorbents, and methods of mercury removal, e.g., from flue gas generated by coal combustion.

The purification method comprises: a step for placing the laden gas stream in contact with a saline solution stream, the saline solution stream comprising, before placement in contact, at least 300 g/l of salts, at least part of the quantity of volatile organic compound being extracted from the laden gas stream and absorbed by the saline solution stream, the placement in contact step producing a purified gas stream containing a residual quantity of volatile organic compound and a laden saline solution stream; a step for recovering the volatile organic compound, comprising a sub-step for decanting a laden saline solution stream, leading to the separation of a phase containing the volatile organic compound and of the saline solution.

An apparatus and process are provided for electricity production and high-efficiency trapping of carbon dioxide, using carbon dioxide within combustion exhaust gas and converging technologies associated with a carbon dioxide absorption tower and a generating device using ions which uses a difference in concentration of salinity between seawater and freshwater. It is expected that enhanced electrical energy production efficiency, an effect of reducing costs for the operation of a carbon dioxide trapping process, and electricity production from carbon dioxide, which is a greenhouse gas, can be simultaneously achieved by increasing the difference in concentration using an absorbent for absorbing carbon dioxide.

The present invention discloses a method for ammonium-enhanced flue gas desulfurization (FGD) by using red mud slurry. The method specifically includes: crushing red mud, sieving the crushed red mud, slurrying the red mud, conducting aeration treatment, adding an ammonium salt and/or ammonia, and conducting natural sedimentation to obtain pretreated red mud slurry and pretreated red mud liquor; adding an ammonium salt and/or ammonia to the slurry, adding water and conducting uniform mixing, conducting pre-FGD, conducting deep desulfurization on treated flue gas by using the pretreated red mud liquor, and directly discharging desulfurized flue gas; and charging the pretreated red mud slurry and the pretreated red mud liquor obtained after the treatment to a replacement tank below, adding lime milk to the replacement tank, conducting stirring and natural sedimentation, conducting soilization on subnatant thick red mud slurry, and refluxing the supernatant to a red mud aeration tank.

The present invention relates to a process for taking up one or more nitrogen oxide(s) from a gaseous and/or aerosol or liquid medium using at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material as well as an adsorbing material comprising said at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material.

Techniques for removing sulfur compounds from a sulfur-containing gas stream can include contacting the gas with an absorption solution comprising a metal cation capable of reacting with the sulfur compound to form a metal sulphide precipitate and/or a metal mercaptide precipitate. In addition, the treatment can include controlling a concentration of the precipitates below a threshold to maintain rheological properties; subjecting the precipitate-enriched solution to vitalization; subjecting the precipitate-enriched solution to regeneration including oxidation; and/or other features to enhance the sulfur removal operations.

The present invention is directed to a process for the removal of aromatic hydrocarbons from a lean acid gas containing less than 20 mol. % of H.sub.2S, comprising: a) contacting the lean acid gas stream (1) with a H.sub.2S-selective liquid absorbent solution (29) in a first absorption zone (2) to produce a gas stream depleted in H.sub.2S (3) and an absorbent solution enriched in H.sub.2S (4), b) introducing the absorbent solution (4) into a non-thermic stripping zone (8) where it is contacted with a stripping gas stream (7) to obtain an absorbent solution depleted in C.sub.4.sup.+ aliphatic and aromatic hydrocarbons (9) and a stripping gas stream enriched in aromatic and C.sub.4.sup.+ aliphatic hydrocarbons (10), c) contacting the stripping gas stream (10) obtained in step b) with a H.sub.2S-selective liquid absorbent solution (28) in a second absorption zone (12) to obtain a stripping gas stream depleted in H.sub.2S (13), and an absorbent solution enriched in H.sub.2S (14) d) introducing the absorbent solution (9) obtained in step b) into a desorption zone (16) wherein the H.sub.2S-selective liquid absorbent solution (17) is recovered and a lean acid gas is produced.

The present invention relates to a process for taking up one or more nitrogen oxide(s) from a gaseous and/or aerosol or liquid medium using at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material as well as an adsorbing material comprising said at least one particulate earth alkali carbonate-comprising material and/or at least one particulate earth alkali phosphate-comprising material.