[{CpFe(CO) 2 } 2 l-(NH 2 (CH 2 ) n NH 2 )](BF 4 ) 2 (n = 2-4) (3), respectively. These complexes have been fully characterized and the mass spectral patterns of complexes 2 are reported. The structures of compounds 2a (n = 2) and 2b (n = 3) have been confirmed by single crystal X-ray crystallography. The single crystal X-ray diffraction data show that complex 2a, [CpFe(CO) 2 NH 2 (CH 2 ) 2 CH 3 ]BF 4 , crystallizes in a triclinic P 1 space group while 2b, [CpFe(CO) 2 NH 2 (CH 2 ) 3 CH 3 ]BF 4 , crystallizes in an orthorhombic Pca2 1 space group with two crystallographically independent molecular cations in the asymmetric unit. Furthermore, the reaction of 1 with 1-alkenes gives the g 2 -alkene complexes in high yield.

No abstract

Key indicators: single-crystal X-ray study; T = 100 K; mean (C-C) = 0.003 Å; R factor = 0.033; wR factor = 0.084; data-to-parameter ratio = 18.0.The asymmetric unit of the title compound, [Fe 2 (C 5 H 5 ) 2 -(C 2 H 8 N 2 )(CO) 4 ](BF 4 ) 2 , contains two half-cations, each located on a center of symmetry, and two tetrafluoridoborate anions. The iron atoms adopt a three-legged piano-stool geometry. All amine H atoms are involved in N-HÁ Á ÁF hydrogen bonds, which consolidate the crystal packing along with weak C-HÁ Á ÁO and C-HÁ Á ÁF interactions. Related literature

No abstract

Due to climate change and anthropogenic activities such as agriculture, mining, and urbanization, water contamination has become a very real modern problem. Modern solutions such as activated carbon, reverse osmosis, and ultrafiltration, among others, have been employed in the decontamination of water. These methods are, however, expensive to set up and maintain and therefore have proved a challenge to implement in developing countries. Zeolite materials exhibit excellent structural properties, such as high ion exchange capacity, porosity, and relative surface area, which make them attractive to water decontamination processes. However, conventional zeolites are expensive, and recent research has focused on utilizing low-cost materials such as agro-wastes and clays as raw materials for the synthesis of zeolites. This review aims to discuss the role of low-cost zeolites in their removal of heavy metals and the feasibility of agro-wastes and natural clays in the synthesis of zeolites. Recent research studies based on the synthesis of zeolites from clays and agro-wastes and their application in heavy metal removal have been reviewed and discussed. Agro-wastes such as rice husk ash and sugarcane bagasse ash and layered silicate clays such as kaolinite and smectites are particularly of interest to zeolite synthesis due to their high silica to alumina ratio. Zeolites synthesized through various methods such as hydrothermal, molten salt, and microwave irradiation synthesis have been discussed with their effect on the adsorption of various heavy metals.

In the presence of significant quantities of carbon dioxide (CO2) and elevated temperatures in the atmosphere due to climate change, cement-based materials are susceptible to carbonation. Blended cements are more prone to carbonation attack than Portland cement. There is a need to evaluate the carbonation resistance of blended cements in a carbonation-prone environment. This paper presents experimental findings obtained from an evaluation of carbonation resistance tests on Rice Husk Ash- (RHA-) blended cement. The blended cement was made by intergrinding of Portland Cement (PC) and RHA to make the test cement (PC-RHA). The RHA dosage in the PC-RHA was varied from 0 to 30% by mass of PC. Pozzolanicity, standard consistency, and setting time tests were conducted on PC-RHA. Mortar prisms measuring 160 mm × 40 mm x 40 mm were separately cast at a water/cement ratio ( w / c ) of 0.50 and 0.60 and cured in water for 2, 7, 14, 28, and 90 days. Compressive strength tests were conducted on the mortar prisms at each of the testing ages. The prepared mortars were also subjected to accelerated carbonation tests in two Relative Humidity (RH) curing regimes, one maintained at an RH greater than 90% and the other between 50–60%. Carbonation resistance of the mixtures was evaluated in terms of the changes in carbonation depth using a phenolphthalein test at the age of 7, 14, 28, and 56 days of curing in a continuous flow of CO2. Compressive strength measurements were also taken during each of the carbonation testing ages. For comparison, similar tests were conducted using commercial PC. The results showed that PC-RHA was pozzolanic while PC was nonpozzolanic. Higher water demand and longer setting times were observed in PC-RHA than in PC. Moreover, there was increased strength development in water-cured samples with increased curing duration. Carbonation results indicated that there was a marked increase in carbonation depth with increased dosage of RHA in PC-RHA binders, increased duration of exposure to CO2, and decreased RH (RH between 50–60%). PC-RHA binders exhibited lower carbonation resistance than PC. In conclusion, for mortars at any w / c ratio, carbonation resistance decreased with increase in RHA dosage and increased w / c ratio.

No abstract

No abstract