Sodium terbium(III) polyphosphate.

Single crystals of the title compound, NaTb(PO(3))(4), were obtained by solid-state reaction. This compound belongs to type II of long-chain polyphosphates with the general formula A(I)B(III)(PO(3))(4). It is isotypic with the NaNd(PO(3))(4) and NaEr(PO(3))(4) homologues. The crystal structure is built up of infinite crenelated chains of corner-sharing PO(4) tetra-hedra with a repeating unit of four tetra-hedra. These chains, extending parallel to [100], are linked by isolated TbO(8) square anti-prisms, forming a three-dimensional framework. The Na(+) ions are located in channels running along [010] and are surrounded by six oxygen atoms in a distorted octa-hedral environment within a cut-off distance <2.9 Å.

KPr(PO(3))(4).

Single crystals of the title compound, potassium praseodymium(III) polyphosphate, were obtained by solid-state reaction. The monoclinic non-centrosymmetric structure is isotypic with all other KLn(PO(3))(4) analogues from Ln = La to Er, inclusive. The crystal structure of these long-chain polyphosphates is built up from infinite crenelated polyphosphate chains of corner-sharing PO(4) tetra-hedra with a repeating unit of four tetra-hedra. These chains, running along [100], are arranged in a pseudo-tetra-gonal rod packing and are further linked by isolated PrO(8) square anti-prisms [Pr-O = 2.3787 (9)-2.5091 (8) Å], forming a three-dimensional framework. The K(+) ions reside in channels parallel to [010] and exhibit a highly distorted coordination sphere by eight O atoms at distances ranging from 2.7908 (9) to 3.1924 (11) Å.

The type IV polymorph of KEu(PO(3))(4).

Single crystals of KEu(PO(3))(4), potassium europium(III) polyphosphate, were obtained by solid-state reactions. This monoclinic form is the second polymorph described for this composition and belongs to type IV of long-chain polyphosphates with general formula A(I)B(III)(PO(3))(4). It is isotypic with its KEr(PO(3))(4) and KDy(PO(3))(4) homologues. The crystal structure is built of infinite helical chains of corner-sharing PO(4) tetra-hedra with a repeating unit of eight tetra-hedra. These chains are further linked by isolated EuO(8) square anti-prisms, forming a three-dimensional framework. The K(+) ions are located in pseudo-hexa-gonal channels running along [01] and are surrounded by nine O atoms in a distorted environment.

Relevance of Toxicity Assessment in Wastewater Treatments: Case Study-Four Fenton Processes Applied to the Mineralization of C.I. Acid Red 14.

Fenton and Fenton-like processes, both in homogeneous and heterogeneous phases, have been applied to an aqueous solution containing the dye AR 14 in order to study the mineralization and toxicity of the solutions generated after color elimination. The mineralization of AR 14 occurred slower than the decolorization. The Microtox analysis of the treated solutions showed low toxicity intrinsic to the chemicals used in the process rather than the degradation products obtained after the treatment of the dye solution. The dye degradation for the Fenton oxidation process was initially faster than for the Fenton-like process but after a short time, the four processes showed similar degradation yields. All processes have shown good results being the heterogeneous process the most convenient since the pH adjustment is not necessary, the catalyst is recovered and reused and the generation of contaminated sludge is avoided.

Rapid decolourization and mineralization of the azo dye C.I. Acid Red 14 by heterogeneous Fenton reaction.

The decolourization and mineralization of a solution of an azo dye using a catalyst based on Fe(II) supported on Y Zeolite (Fe(II)-Y Zeolite) and adding hydrogen peroxide (heterogeneous Fenton process) have been studied. The catalyst was prepared by ion exchange, starting from a commercial ultra-stable Y Zeolite. All experiments were performed on a laboratory scale set-up. The effects of different parameters such as initial concentration of the dye, initial pH of the solution of the dye, H(2)O(2) concentration, temperature and ratio of amount of catalyst by amount of solution on the decolourization efficiency of the process were investigated. A percentage of colour removal of 99.3±0.2% and a mineralization degree of 84±5% of the solution of the dye were achieved in only 6 min of contact time between the catalyst and the solution, under the following conditions: initial concentration of the dye of 50 ppm, pH 5.96, 8.7 mM of H(2)O(2), T of 80°C and catalyst concentration of 15 g/L. Moreover, the catalyst Fe(II)-Y Zeolite can be easily filtered from the solution, does not leach any iron into the solution (avoiding any secondary contamination due to the metal) and its effectivity can be reproduced after consecutive experiments.