Investigating the hydration of C3A in the presence of the potentially toxic element chromium–a route to remediation?

Pollution by hexavalent chromium is a growing, global problem. Its presence in public water systems is often the result of industrial activities, both past and present. In this study, tricalcium aluminate (C3A, Ca(3)Al(2)O(6)) is added to solutions of varying concentrations of potassium chromate (K(2)CrO(4)) and samples of both the solid and liquid are taken at various time intervals to monitor the removal of chromium from the solutions. Solution concentrations of 0.2 M, 0.1 M, 0.02 M, and 0.01 M are used, and the chromium concentration is found to reduce in all cases. For the 0.02 M solution the chromium concentration is reduced from 1040 ppm to 3.1 ppm in 1 week, and the chromium concentration of the 0.01 M solution is reduced from 520 ppm to 0.26 ppm in only one day of reaction with the C3A. The chromium removed from solution is identified in the solid products, which were fully characterised as being a mixture of ettringite (Ca(6)[Al(OH)(6)](2)(CrO(4))(3)·26H(2)O) and monochromate (Ca(4)[Al(OH)(6)](2)CrO(4)·8H(2)O) phases from analysis of Powder X-ray Diffraction and Fourier Transform Infrared Spectroscopy data. The work presented here is a proof of concept study to investigate C3A as a potential material for the removal of hexavalent chromium from solution. The results from this study are initial steps towards development of this as a technology for hexavalent chromium remediation

Locating hydrogen positions in the autunite mineral metatorbernite [Cu(UO₂)₂(PO₄)₂·8H₂O]:A combined approach using neutron powder diffraction and computational modelling

Metatorbernite [Cu(UO(2))(2)(PO(4))(2)·8H(2)O] is a promising remediation material for environmental uranium contamination. Previous X-ray diffraction studies have been unable to definitively locate hydrogen positions within metatorbernite, which are key to determining the hydrogen-bond network that helps to stabilize the structure. Here, hydrogen positions have been determined using a combination of neutron powder diffraction and the computational modelling technique ab initio random structure searching (AIRSS). Atomic coordinates determined through Rietveld analysis of neutron powder diffraction data are in excellent agreement with the minimum energy configuration predicted by AIRSS; thus, simulations confirm that our proposed model likely represents the global minimum configuration. Two groups of water molecules exist within the metatorbernite structure: free water and copper-coordinating water. Free water molecules are held within the structure by hydrogen bonding only, whilst the coordinating water molecules bond to copper in the equatorial positions to produce a 4 + 2 Jahn–Teller octahedra. The successful agreement between neutron powder diffraction data and AIRSS suggests that this combined approach has excellent potential for the study of other (trans)uranium materials in which hydrogen bonding plays a key role in phase stability

Themed issue on advances in solid state chemistry and its applications

Peer reviewedPostprin

Selective Gold Precipitation by a Tertiary Diamide Driven by Thermodynamic Control

The simple diamide ligand L was previously shown to selectively precipitate gold from acidic solutions typical of e-waste leach streams, with precipitation of gallium, iron, tin, and platinum possible under more forcing conditions. Herein, we report direct competition experiments to afford the order of selectivity. Thermal analysis indicates that the gold-, gallium-, and iron-containing precipitates present as the most thermodynamically stable structures at room temperature, while the tin-containing structure does not. Computational modeling established that the precipitation process is thermodynamically driven, with ion exchange calculations matching the observed experimental selectivity ordering. Calculations also show that the stretched ligand conformation seen in the X-ray crystal structure of the gold-containing precipitate is more strained than in the structures of the other metal precipitates, indicating that intermolecular interactions likely dictate the selectivity ordering. This was confirmed through a combination of Hirshfeld, noncovalent interaction (NCI), and quantum theory of atoms in molecules (QTAIM) analyses, which highlight favorable halogen···halogen contacts between metalates and pseudo-anagostic C-H···metal interactions in the crystal structure of the gold-containing precipitate.</p

A prospective cohort study assessing clinical referral management & workforce allocation within a UK regional medical genetics service

Abstract Ensuring patient access to genomic information in the face of increasing demand requires clinicians to develop innovative ways of working. This paper presents the first empirical prospective observational cohort study of UK multi-disciplinary genetic service delivery. It describes and explores collaborative working practices including the utilisation and role of clinical geneticists and non-medical genetic counsellors. Six hundred and fifty new patients referred to a regional genetics service were tracked through 850 clinical contacts until discharge. Referral decisions regarding allocation of lead health professional assigned to the case were monitored, including the use of initial clinical contact guidelines. Significant differences were found in the cases led by genetic counsellors and those led by clinical geneticists. Around a sixth, 16.8% (109/650) of referrals were dealt with by a letter back to the referrer or re-directed to another service provider and 14.8% (80/541) of the remaining patients chose not to schedule an appointment. Of the remaining 461 patients, genetic counsellors were allocated as lead health professional for 46.2% (213/461). A further 61 patients did not attend. Of those who did, 86% (345/400) were discharged after one or two appointments. Genetic counsellors contributed to 95% (784/825) of total patient contacts. They provided 93.7% (395/432) of initial contacts and 26.8% (106/395) of patients were discharged at that point. The information from this study informed a planned service re-design. More research is needed to assess the effectiveness and efficiency of different models of collaborative multi-disciplinary working within genetics services. Keywords (MeSH terms) Genetic Services, Genetic Counseling, Interdisciplinary Communication, Cohort Studies, Delivery of Healthcare, Referral and Consultation

Development of a definition for Rapid Progression (RP) of renal function in HIV-positive persons: the D:A:D study

Background No consensus exists on how to define abnormally rapid deterioration in renal function (Rapid Progression, RP). We developed an operational definition of RP in HIV-positive persons with baseline estimated glomerular filtration rate (eGFR) >90 ml/min/1.73 m2 (using Cockcroft Gault) in the Data Collection on Adverse Events of Anti-HIV Drugs (D:A:D) study from 2004 to 2011. Methods Two definitions were evaluated; RP definition A: An average eGFR decline (slope) ≥5 ml/min/1.73 m2/year over four years of follow-up with ≥3 eGFR measurements/year, last eGFR <90 ml/min/1.73 m2 and an absolute decline ≥5 ml/min/1.73 m2/year in two consecutive years. RP definition B: An absolute annual decline ≥5 ml/min/1.73 m2/year in each year and last eGFR <90 ml/min/1.73 m2. Sensitivity analyses were performed considering two and three years' follow-up. The percentage with and without RP who went on to subsequently develop incident chronic kidney disease (CKD; 2 consecutive eGFRs <60 ml/min/1.73 m2 and 3 months apart) was calculated. Results 22,603 individuals had baseline eGFR ≥90 ml/min/1.73 m2. 108/3655 (3.0%) individuals with ≥4 years' follow-up and ≥3 measurements/year experienced RP under definition A; similar proportions were observed when considering follow-up periods of three (n=195/6375; 3.1%) and two years (n=355/10756; 3.3%). In contrast under RP definition B, greater proportions experienced RP when considering two years (n=476/10756; 4.4%) instead of three (n=48/6375; 0.8%) or four (n=15/3655; 0.4%) years' follow-up. For RP definition A, 13 (12%) individuals who experienced RP progressed to CKD, and only (21) 0.6% of those without RP progressed to CKD (sensitivity 38.2% and specificity 97.4%); whereas for RP definition B, fewer RP individuals progressed to CKD. Conclusions Our results suggest using three years' follow-up and at least two eGFR measurements per year is most appropriate for a RP definition, as it allows inclusion of a reasonable number of individuals and is associated with the known risk factors. The definition does not necessarily identify all those that progress to incident CKD, however, it can be used alongside other renal measurements to early identify and assess those at risk of developing CKD. Future analyses will use this definition to identify other risk factors for RP, including the role of antiretrovirals