Continuous Synthesis of Zn2Al-CO3 Layered Double Hydroxides for the Adsorption of Reactive Dyes from Water

A novel pilot scale approach to continuous synthesis of layered double hydroxides (LDHs) was used to produce Zn2Al-CO3. The Zn2Al-CO3 was calcined and used in the adsorption of Reactive Black 5 (RB5) and Reactive Orange 16 (RO16) from water. The specific surface area of the LDH was 50.1 m2 g-1, while the surface area of the calcined LDH (MMO) was 57.8 m2 g-1. X-ray diffraction indicated complete breakdown of the LDH at 500 °C for 4 hours, with amorphous Al2O3 or AlOOH alongside ZnO. Reaction variables in the adsorption system; temperature, adsorbent dose, pH, initial concentration and the effect of competing anions were investigated across four temperatures from 10 °C to 40 °C. Maximum adsorption capacity calculated from the Langmuir isotherm was 895 mg g-1 and 589 mg g-1 at 20 °C, for RB5 and RO16, respectively. Intercalation of dye molecules was the main mode of adsorption, as indicated by shifts in (003) reflection from 11.5° to 4.5° and 3.2° for RB5 and RO16 respectively. Adsorption was best modelled by the pseudo 2nd order kinetic model. The intra-particle diffusion model indicated multiple stages of adsorption; surface adsorption occurs initially, followed by, intra-particle diffusion of dye molecules into the interlayer region. Regeneration through calcination resulted in an adsorption equal to 99 ± 2%

Natural fluorapatite dissolution kinetics and Mn2+ and Cr3+ metal removal from sulfate fluids at 35 °C

In light of the consequences of global warming and population growth, access to safe drinking water becomes an ever greater challenge, in particular in low to middle income countries in arid regions. Moreover, mining which may cause acid mine drainage and heavy metal contamination puts further pressure on management of limited water resources. Hence, the development of cost effective water treatment methods is critical. Here, using batch reactor experiments we investigate the kinetics and mechanisms behind divalent Mn and trivalent Cr removal from sulfate fluids using natural fluorapatite at 35 °C. The results show that the fluorapatite dissolution rate depends on fluid pH, and that dissolution is the dominant mechanism in fluids with pH below 4. Apatite can thus serve as remediation to neutralize acidic fluids. Fluid pH of 4–6 triggers a dissolution-precipitation mechanism, in some cases following upon a dissolution-only period, with the formation of a metal phosphate. In these experiments, Cr removal is two to ten times faster than Mn removal given similar solution pH. The results demonstrate that natural apatite represents a promising, cost effective material for use in passive remediation of mining-induced contamination of soils and groundwater in arid regions

Analysis of conjugated steroid androgens: Deconjugation, derivatisation and associated issues

AbstractGas chromatography/mass spectrometry (GC/MS) is the preferred technique for the detection of urinary steroid androgens for drug testing in athletics. Excreted in either the glucuronide or sulfated conjugated form, steroids must first undergo deconjugation followed by derivatisation to render them suitable for GC analysis. Discussed herein are the deconjugation and the derivatisation preparative options. The analytical challenges surrounding these preparatory approaches, in particular the inability to cleave the sulfate moiety have led to a focus on testing protocols that reply on glucuronide conjugates. Other approaches which alleviate the need for deconjugation and derivatisation are also highlighted

Freshwater and airborne textile fibre populations are dominated by ‘natural’, not microplastic, fibres

The potential role of natural textile fibres as environmental pollutants has been speculated upon by some environmental scientists, however, there is a general consensus that their biodegradability reduces their environmental threat. Whilst the risks that they pose remain poorly understood, their environmental prevalence has been noted in several recent microplastic pollution manuscripts. Here we highlight the extent to which natural textile fibres dominate fibre populations of upstream reaches of the River Trent, UK, as well as the atmospheric deposition within its catchment, over a twelve month microplastic sampling campaign. Across 223 samples, natural textile fibres represented 93.8% of the textile fibre population quantified. Moreover, though microplastic particles including synthetic fibres are known to be pervasive environmental pollutants, extruded textile fibres were absent from 82.8% of samples. Natural textile fibres were absent from just 9.7% of samples

Rational design of thermostable carbonic anhydrase mutants using molecular dynamics simulations

The stability of enzymes is critical for their application in industrial processes, which generally require different conditions from the natural enzyme environment. Both rational and random protein engineering approaches have been used to increase stability, with the latter requiring extensive experimental effort for the screening of variants. Moreover, some general rules addressing the molecular origin of protein thermostability have been established. Herein, we demonstrate the use of molecular dynamics simulations to gain molecular level understanding of protein thermostability and to engineer stabilizing mutations. Carbonic anhydrase (CA) is an enzyme with a high potential for biotechnological carbon capture applications, provided it can be engineered to withstand the high temperature process environments, inevitable in most gas treatment units. In this study, we used molecular dynamics simulations at 343, 353, and 363 K to study the relationship between structure flexibility and thermostability in bacterial α-CAs and applied this knowledge to the design of mutants with increased stability. The most thermostable α-CA known, TaCA from Thermovibrio ammonificans, had the most rigid structure during molecular dynamics simulations, but also showed regions with high flexibility. The most flexible amino acids in these regions were identified from root mean square fluctuation (RMSF) studies, and stabilizing point mutations were predicted based on their capacity to improve the calculated free energy of unfolding. Disulfide bonds were also designed at sites with suitable geometries and selected based on their location at flexible sites, assessed by B-factor calculation. Molecular dynamics simulations allowed the identification of five mutants with lower RMSF of the overall structure at 400 K, compared to wild-type TaCA. Comparison of free-energy landscapes between wild-type TaCA and the most promising mutants, Pro165Cys–Gln170Cys and Asn140Gly, showed an increased conformational stability of the mutants at 400 K

Intelligent Resource Use to Deliver Waste Valorisation and Process Resilience in Manufacturing Environments

© 2020 Johnson Matthey Circular economy (CE) thinking has emerged as a route to sustainable manufacture, with related cradle-to-cradle implications requiring implementation from the design stage. The challenge lies in moving manufacturing environments away from the traditional linear economy paradigm, where materials, energy and water have often been designed to move out of the system and into receivership of waste management bodies after use. Recent applications of industrial digital technologies (IDTs: for example internet of things, data-driven modelling, cyber-physical systems, cloud manufacturing, cognitive computing) to manufacturing may be instrumental in transforming manufacturing from linear to circular. However, although IDTs and CE have been the focus of intensive research, there is currently limited research exploring the relationship between IDTs and the CE and how the former may drive the implementation of CE. This article aims to close the knowledge gap by exploring how an IDT (data-driven modelling) may facilitate and advance CE principles within process manufacturing systems, specifically waste valorisation and process resilience. These applications are then demonstrated through two real-world manufacturing case studies: (a) minimising resource consumption of industrial cleaning processes and (b) transforming wastewater treatment plants (WWTPs) into manufacturing centres

Translating wastewater reuse for irrigation from OECD Guidelines: Tramadol sorption and desorption in soil-water matrices.

Treated and untreated wastewater is often used for agricultural irrigation and, despite the many benefits of this practice, it poses the risk of biologically active chemical pollutants (such as pharmaceuticals, like tramadol) entering the environment. The partitioning of tramadol between soil/water at environmentally relevant concentrations is important to understand its environmental toxicity. Kinetics and isotherm sorption studies based on the Organisation for Economic Cooperation and Development (OECD) 106 Guideline were undertaken, ensuring comparability to previous studies. Studies were undertaken in three soils of different characteristics using aqueous concentrations of tramadol from 500 ng L−1 (environmentally relevant) to 100 μg L−1 (comparable to previous studies). Two of the soils presented a significantly (p < 0.05) higher sorption at a lower initial tramadol concentration (5000 ng L−1), compared to 20,000 ng L−1. Hysteresis was observed in all studied soils, indicating the accumulation of tramadol. Higher sorption to soils correlated with higher clay content, with soil/water partitioning coefficients (Kd) of 5.5 ± 13.3, 2.5 ± 3.8 and 0.9 ± 3.0 L kg1 for soils with clay contents of 41.9%, 24.5% and 7.4%, respectively. Cation exchange was proposed as the main sorption mechanism for tramadol to soils when the pH was below tramadol's pKa values (9.41 and 13.08). A comparative kinetics study between tramadol in soil/calcium chloride buffer and soil/wastewater effluent demonstrated significantly higher (p < 0.05) tramadol sorption to soil from wastewater effluent. This has the environmental implication that clay soils will be able to retain tramadol from irrigation water, despite the organic content of the irrigation water. Therefore, our studies show that tramadol soil sorption is likely to be higher in agricultural environments reusing wastewater than that predicted from experiments using the OECD 106 Guideline calcium chloride buffer

Modelling Emerging Pollutants in Wastewater Treatment: A Case Study using the Pharmaceutical 17??ethinylestradiol

Mathematical modelling can play a key role in understanding as well as quantifying uncertainties surrounding the presence and fate of emerging pollutants in wastewater treatment processes (WWTPs). This paper presents for the first time a simplified emerging pollutant pathway in the WWTP that incorporates two potential pathways to sequestration. It develops de-terministic and stochastic ordinary differential equations to gain insight into the fate and behaviour of a case study pharmaceutical, with particular focus on sorption to the solid phase, as well as the nature of the experimentally measured solid parent compound. Statistical estimation and inferential procedures are developed and via a proof-of-concept examination, the study explores the transformation pathways of the bioactive chemicals (BACs) in the bioreactor, which is the heart of the WWTP. With a focus on the case study pharmaceutical 17??ethinlyestradiol (EE2), the simulation results show good agreement with the EE2 data. In addition, the results suggest that the experimentally measured solid EE2-parent concentration is very similar to the model-based sequestered EE2-parent concentration

Ultrasound Biomicroscopy Comparison of Ab Interno

Purpose. To compare ab interno and ab externo scleral fixation of posterior chamber intraocular lenses (PCIOL) using ultrasound biomicroscopy (UBM). Methods. Randomized patients underwent ab externo or ab interno scleral fixation of a PCIOL. Ultrasound biomicroscopy was performed 3 to 6 months postoperatively, to determine PCIOL centration, IOL distance to the iris at 12, 3, 6, and 9 hours, and haptics placement in relation to the ciliary sulcus. Results. Fifteen patients were enrolled in the study. The ab externo technique was used in 7 eyes (46.6%) and the ab interno in 8 eyes (53.3%). In the ab externo technique, 14 haptics were located: 4 (28.57%) in the ciliary sulcus; 2 (14.28%) anterior to the sulcus; and 8 (57.14%) posterior to the sulcus, 6 in the ciliary body and 2 posterior to the ciliary body. In the ab interno group, 4 haptics (25.0%) were in the ciliary sulcus, 2 (12.50%) anterior to the sulcus, and 10 (75.0%) posterior to the sulcus, 4 in the ciliary body and 6 posterior to the ciliary body. Conclusions. Ab externo and ab interno scleral fixation techniques presented similar results in haptic placement. Ab externo technique presented higher vertical tilt when compared to the ab interno

Evaluation of photoanode materials used in biophotovoltaic systems for renewable energy generation

Biological photovoltaic (BPV) cells are living solar panels capable of producing clean energy by extracting electrons from sunlight (in daytime) and stored carbon in microbial cells (during the night or on cloudy days), irrespective of the organic substrate supply. The physicochemical properties of anode surfaces harbouring microbial communities in BPV systems influence the electrochemical charge transfer rate at the electrode. Hence, these properties play a significant role in regulating the kinetics of metabolic reactions in the biotic compartment while providing an electron transfer path. Various electrically conductive materials have been explored as solid-state anodes to improve the power output and economic viability of BPV systems. However, the current systems still suffer from low power density due to electrodes' electrochemical limitations and a lack of systematic optimization of the device. This review provides a comprehensive insight into the recent developments in different anode materials, their dimensional structure, and their impact on the performance of BPV systems in the last two decades. Moreover, the existing limitations of electrode materials in BPV systems are summarized, and outlooks for future anode advancements are foreseen