Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 9 de 9
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Environ Manage ; 254: 109752, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31733478

RESUMO

Awareness about the rising detection and reported (eco)toxicological effects of contaminants of emerging concern (CECs, e.g. pharmaceuticals and personal care products - PPCPs - and modern pesticides) in the aquatic environment is growing. CECs are increasingly reported in the African aquatic environment, although the amount of data available is still limited. In this work, a comprehensive review is presented on the occurrence of CECs in wastewater, sludge, surface water, sediment, groundwater and drinking water of Africa. Further attention is given to the performance of wastewater stabilization ponds (WSPs) and trickling filters (TF) with respect to CECs removal. For the first time, we also look at the state of knowledge on the performance of point-of-use technologies (POUs) regarding the removal of CECs in drinking water. Generally, CECs in Africa occur at the same order of magnitude as in the Western world. However, for particular groups of compounds and at specific locations such as informal settlements, clearly higher concentrations are reported in Africa. Whereas antiretroviral and antimalarial drugs are rarely detected in the Western world, occurrence patterns in Africa reveal concentrations up to >100 µg L-1. Removal efficiencies of WSPs and TFs focus mainly on PPCPs and vary significantly, ranging from no removal (e.g. carbamazepine) to better than 99.9% (e.g. paracetamol). Despite the rising adoption of POUs, limited but promising information is available on their performance regarding CECs treatment in drinking water, particularly for the low-cost devices (e.g. ceramic filters and solar disinfection - SODIS) being adopted in Africa and other developing countries.


Assuntos
Praguicidas , Preparações Farmacêuticas , Poluentes Químicos da Água , África , Monitoramento Ambiental , Águas Residuárias
2.
Sci Total Environ ; 637-638: 336-348, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-29751313

RESUMO

Although there is increased global environmental concern about emerging organic micropollutants (EOMPs) such as pharmaceuticals, personal care products (PPCPs) and polar pesticides, limited information is available on their occurrence in Africa. This study presents unique data on concentrations and loads of 31 PPCPs and 10 pesticides in four wastewater stabilization ponds (WSPs) and receiving rivers (flowing through urban centres) in Kenya. The WSPs indicate a high potential to remove pharmaceutically active compounds (PhACs) with removals by up to >4 orders of magnitude (>99.99% removal), mainly occurring at the facultative stage. However, there are large differences in removal among the different classes, and a shift in the relative PhACs occurrence is observed during wastewater treatment. Whereas the influent is dominated by high-consumption PhACs like anti-inflammatory drugs (e.g. paracetamol and ibuprofen, up to 1000 µg L-1), the most recalcitrant PhACs including mainly antibiotics (e.g. sulfadoxin and sulfamethoxazole) and antiretrovirals (e.g. lamivudine and nevirapine) are largely abundant (up to 100 µg L-1) in treated effluent. Overall, concentrations of EOMPs in the Nzoia Basin rivers are the highest in dry season (except pesticides) and in small tributaries. They are of the same order of magnitude as those measured in the western world, but clearly lower than what we recently measured in the Ngong River, Nairobi region. Based on the specific consumption patterns and recalcitrant behavior, high concentrations (>1000 ng L-1) are observed in the rivers for PPCPs like lamivudine, zidovudine, sulfamethoxazole and methylparaben. Concentration levels of pesticides are in general one order of magnitude lower (<250 ng L-1). Our data suggest a continuous input of EOMPs to the rivers from both point (WSPs) and diffuse (urban centres) sources. To better understand and manage the impact of both sources, EOMP removal mechanisms in WSPs and their attenuation in rivers merit further research.


Assuntos
Cosméticos/análise , Monitoramento Ambiental , Praguicidas/análise , Preparações Farmacêuticas/análise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Quênia , Tanques , Rios , Águas Residuárias/química , Águas Residuárias/estatística & dados numéricos
3.
Acta Crystallogr Sect E Struct Rep Online ; 68(Pt 6): o1731, 2012 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-22719518

RESUMO

The title salt, [NH(3)CH(2)CH(2)NH(2)](+)·I(-), has an array structure based on strong inter-molecular N-H⋯N hydrogen bonding formed between the ammonium and amine groups of adjacent cations. This inter-action gives a helical chain of cations that runs parallel to the b axis. The four remaining NH group H atoms all form hydrogen bonds to the iodide anion, and these iodide anions lie in channels parallel to the cation-cation chains.

4.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 8): m1138, 2011 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-22090898

RESUMO

The asymmetric unit of the title compound, [Ag(NO(2))(C(14)H(14)N(4))](n), contains half of the repeating formula unit (Z' = 1/2). The Ag(I) ion lies on a twofold rotation axis. The primary structure consists of a one-dimensional coordination polymer formed by the Ag(I) ions and the bipyridyl azine ligand in which there is an inversion center at the mid-point of the N-N bond. The nitrite anion inter-acts with the Ag(I) ion through a chelating µ(2) inter-action involving both O atoms. In the crystal, the coordination chains are parallel and inter-act through Ag⋯π [3.220 (2) Å] and π-π [3.489 (3) Å] inter-actions.

5.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 3): o682-3, 2011 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-21522429

RESUMO

The asymmetric unit of the title compound, C(16)H(34)N(4) (2+)·2I(-)·2H(2)O, contains one half-cation, one iodide anion and one water mol-ecule. The cation has crystallographically imposed centrosymmetric symmetry. Despite some differences in the unit-cell dimensions, packing analysis on a cluster of 15 cations and a comparison of the hydrogen bonding suggests that this compound is isostructural with its bromide analogue. Inter-molecular hydrogen bonding forms eight-membered [H-O-H⋯I](2) and [H-N-H⋯I](2) rings and creates a sheet structure.

6.
Acta Crystallogr Sect E Struct Rep Online ; 66(Pt 10): m1330-1, 2010 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-21587462

RESUMO

Crystallizing the cobalt(II) salt of the azo dye Orange G from water was found to give the solvent-separated ion-pair species hexa-aqua-cobalt(II) 7-oxo-8-(2-phenyl-hydrazin-1-ylidene)-7,8-dihydro-naphthalene-1,3-disulfonate tetra-hydrate, [Co(H(2)O)(6)](C(16)H(10)N(2)O(7)S(2))·4H(2)O. The asymmetric unit of the cobalt(II) salt contains three independent octa-hedral [Co(OH(2))(6)](2+) cations, three azo anions, all with similar configurations, and 12 uncoordinated water mol-ecules. The structure is closely related to that of one of the known magnesium analogues. Both structures have Z' = 3, feature nearly planar azo anions [maximum displacement of azo-N atoms from the plane of the phenyl ring = 0.058 (7) Å] in their hydrazone tautomeric form, form layer structures with hydro-philic and hydro-phobic layers alternating along the b-axis direction, and are stabilized by an extensive network of hydrogen bonds..

7.
Acta Crystallogr Sect E Struct Rep Online ; 66(Pt 8): o2110, 2010 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-21588401

RESUMO

The title compound, C(14)H(12)O(2), has an essentially planar conformation with the two aromatic rings forming a dihedral angle of 5.23 (9)° and the aldehyde group lying in the plane of its aromatic group [maximum deviation = 0.204 (3) Å]. Weak inter-molecular C-H⋯O contacts are found to be shortest between the aldehyde O-atom acceptor and the H atoms of the methyl-ene group.

8.
Acta Crystallogr Sect E Struct Rep Online ; 66(Pt 11): o2984-5, 2010 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-21589150

RESUMO

The title compound, C(15)H(13)NO(3), crystallizes with three independent mol-ecules per asymmetric unit (Z' = 3). One of these mol-ecules is found to have a configuration with a greater twist between its two aromatic rings than the other two [compare 70.26 (13) and 72.31 (12)° with 84.22 (12)°]. There are also differences in the number and nature of the weak inter-molecular C-H⋯O contacts formed by each of the three mol-ecules.

9.
Acta Crystallogr C ; 59(Pt 11): o650-2, 2003 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-14605419

RESUMO

The antibiotic cephalexin [systematic name: D-7-(2-amino-2-phenylacetamido)-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid] forms a range of isomorphic solvates, with the maximum hydration state of two water molecules formed only at high relative humidities. The water content of the structure reported here (C(16)H(17)N(3)O(4)S.1.9H(2)O) falls just short of this configuration, having three independent cephalexin molecules, one of which is disordered, and 5.72 observed water molecules in the asymmetric unit. The facile nature of the cephalexin solvation/desolvation process is found to be facilitated by a complex channel structure, which allows free movement of solvent in the crystallographic a and b directions.


Assuntos
Antibacterianos/química , Cefalexina/química , Canais Iônicos/química , Água/química , Cristalografia por Raios X , Ligações de Hidrogênio , Modelos Moleculares , Conformação Molecular
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA