Search

This study aims to improve the pore volume and specific surface area of kaolinite (Kaol) and montmorillonite (Mt) through low-temperature acid treatment to address their limited adsorption capacity. Clay mineral samples underwent sulfuric acid activation at various concentrations and durations. SEM analysis indicated acid activation improved kaolinite pore structure, increasing specific surface area, while montmorillonite exhibited reduced grain size and higher porosity, resulting in greater pore volume and surface area. EDX analysis revealed changes in chemical composition, including a 10% increase in silica and a 13% reduction in aluminium in kaolinite, whereas montmorillonite exhibited a 13% aluminium increase and 9.5% higher silica content. Kaolinite's XRD pattern remained unchanged, resisting 2.5 M acid activation, while montmorillonite displayed modified patterns, indicating interlayer conversion with increased acid concentration. BET analysis confirmed higher sulfuric acid concentration increased pore volume and surface area, while FTIR analysis showed stable Si–O stretching peaks with changing intensity after 8 h. Montmorillonite exhibited Al–OH and Mg–OH bands, decreasing with higher acid concentration, and Si–O–Fe and Si–O–Al bonds disappeared with acid activation. Thus, the results indicate significantly enhanced pore volume and specific surface area after acid activation, accelerating CO2 adsorption rates. This activation demonstrates a direct relationship between acid concentration and reaction time with clay minerals' pore characteristics. These clay minerals can be used as adsorbents for CO2 in carbon capture technology, aiding the global goal of achieving 'net zero' emissions by 2050. [ABSTRACT FROM AUTHOR]

Both sludge biochar (BC) and activated coke (ACO) are hierarchical while their surface properties have a large disparity. We show that sludge biochar pyrolyzed at 600°C (BC600) outperforms biochar produced at other temperatures for a range of biomass feedstock. BC600 displays lower carbon content, lower surface area, and importantly more abundant surface oxygen-containing functional groups when compared with ACO. BC600 and ACO were used to activate peroxydisulfate (PDS) for tetracycline oxidation while the degradation mechanisms were comprehensively discussed. Interestingly, ACO demonstrated a particularly higher performance where activating PDS compared with BC600. The Kapp value for the synergetically combined ACO-PDS process was 2.15 times that of the sum of adsorption and PDS oxidation processes alone, while it was 1.72 times for the BC600-PDS process. Solution pH had a more dramatic influence on BC600 than on ACO. Quenching experiments proved that both OH• and SO4 •-contributed insignificantly while most of the degradation was attributed to superoxide radical (O2 •-), singlet oxygen (1O2), and active holes (h+). After reducing carbonyl groups on both carbons by KBH4 in absolute alcohol, quenching experiments did not indicate the key role of carbonyl groups for 1O2 generation. Nonradical pathway proved dominant in the carbon/PDS catalytic process. Excellent reusability and stability for ACO was observed in repeated use experiments. [ABSTRACT FROM AUTHOR]

A multiscale network integration approach introduced by Jiang et al. (2013) is used to generate a representative pore-network for a carbonate rock with a pore size distribution across several orders of magnitude. We predict the macroscopic flow parameters of the rock utilising (i) 3-D images captured by X-ray computed microtomography and (ii) pore-network flow simulations. To capture the multiscale pore size distribution of the rock, we imaged four different rock samples at different resolutions and integrated the data to produce a pore-network model that combines information at several length-scales that cannot be recovered from a single tomographic image. A workflow for selection of the number and length-scale of the required input networks for the network integration process, as well as fine tuning the model parameters is presented. Mercury injection capillary-pressure data were used to evaluate independently the multiscale networks. We explore single-scale, two-scale, and three-scale network models and discuss their representativeness by comparing simulated capillary-pressure versus saturation curves with laboratory measurements. We demonstrate that for carbonate rocks with wide pore size distributions, it may be required to integrate networks extracted from two or three discrete tomographic data sets in order to simulate macroscopic flow parameters. [ABSTRACT FROM AUTHOR]

Cyanotoxins pose a health threat when present in the drinking water supply since conventional water treatment processes are not effective in removing extracellular metabolites hence, advanced treatment techniques are usually applied. Powdered activated carbon (PAC) is an effective adsorbent for removing toxins. However, since a high volume is necessary, alternative adsorbents have been investigated. Biochar, especially from renewable sources, is a potential adsorbent material that could replace PAC for removing toxins. This paper aimed to investigate which PAC properties play key roles in cyanotoxin adsorption by a systematic review addressing the adsorption of toxins such as microcystins-LR (MC-LR), cylindrospermopsin (CYL), and saxitoxins (STXs). As a result, the review showed that some commonly adopted indices (i.e. total surface area) are not relevant to cyanotoxin adsorption, especially if appraised alone. Along with a multi-barrier approach, PAC has to be applied taking into account the complexity of the water system, which includes a better understanding of the characteristics of the adsorbent, the target toxin, and the aqueous medium. The biochar systematic review showed that no studies have yet been designed specifically for the removal of toxins. Since biochar has not yet been applied to water treatment processes, the knowledge gap is even greater than for PAC.

Charcoal production and utilisation are linked to various health issues and occupational hazards. However, to our knowledge, no systematic review has primarily focused on the health implications of charcoal production and its use while distinguishing charcoal from other solid fuels such as wood and coal., Objectives: This systematic review presents a synthesis of the evidence on the health risks associated with producing and using charcoal across the world., Design: Systematic review using a systematic narrative synthesis approach., Data Sources: MEDLINE (through Ovid interface), CINAHL, Embase, Web of Science, PsycINFO, Cochrane Library and SCOPUS, from inception to 26 February 2021., Eligibility Criteria for Selecting Studies: Peer-reviewed journal articles reporting empirical findings on the associations between charcoal usage/production and health parameters., Data Extraction and Synthesis: Two independent reviewers extracted data and assessed the quality of primary studies., Results: Our findings showed that charcoal production and usage are linked with specific adverse health outcomes, including respiratory diseases (n=21), cardiorespiratory and neurological diseases (n=1), cancer (n=3), DNA damage (n=3), carbon monoxide (CO) poisoning (n=2), physical injury (n=2), sick house syndrome (n=1), unintentional weight loss and body mass index (BMI) reduction (n=2), increase in blood pressure (n=1) and CO death (n=1). Among the included articles that reported respiratory diseases (n=21), there was one case of asthma and tuberculosis and two cases of chronic obstructive pulmonary disease., Conclusions: This review links charcoal production/usage and some associated human health risks. These include respiratory diseases and other non-respiratory illnesses such as sick-building syndrome, cardiovascular diseases, DNA damage, CO poisoning and death, unintentional weight loss and BMI reduction, and physical injuries., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Advances in computational and image acquisition capabilities have made direct simulation of multiphase fluid flow through porous media possible. An example is application of volume of fluid modeling on images produced using the X-ray computed micro-tomography technique. Analysis of such high-resolution (both temporal and spatial) data sets provides new insights into pore-scale dynamics of previously less well-known processes. We present the outcomes of a high-resolution direct-simulation two-phase fluid displacement study performed on a series of five two-dimensional images of sandy porous media produced using erosion and dilation algorithms. This has enabled us to study the pore-scale dynamics systematically in models that are similar in connectivity but different in the morphology (pore sizes and aspect ratio). Our results show that the drainage and imbibition processes result in very distinct fluid displacement patterns in these models at the pore scale. As a result of drainage, the more open (eroded grains) models accommodate large oil clusters, while the tighter (dilated grains) models trap smaller oil clusters. The imbibition process is dominated by oil trapping in two ways: (i) bypassing larger oil clusters in the eroded models and (ii) local trapping of smaller clusters in the dilated models. This behavior is shown to arise from the relatively larger average aspect ratios of the dilated models compared to those of the eroded models. This promotes snap-off at pore throats (in competition with piston-like displacement), resulting in local trapping of the non-wetting phase. Both of these pore-scale trapping regimes seen here allow trapping of oil in as much as 50% of the pore space. Through the use of erosion and dilation operations, we show that a power-law relationship exists between the average pore size and the average grain size for these sandy media. This relationship is useful in designing engineered porous materials where pore sizes need to be estimated based on grain sizes., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)