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This work is financially supported by the National Metal and Materials Technology Center, Thailand. Hypercrosslinked polymers (HCPs) are typically synthesised over 24-hour batch reactions, limiting the ability to improve productivity rates during the scale up production of HCPs. Continuous flow synthesis can potentially overcome this limitation but the formation of insoluble HCP products, compounded by HCP expansion due to solvent adsorption during synthesis, clogged the flow reactors. In this study, we overcome clogging issues associated with both insoluble reagents and HCP products through reactor design and optimisation of synthesis time by an average of 99 %. Using this reactor, we synthesised HCPs via three known crosslinking strategies underpinned by Friedel-Crafts alkylation – internal, post-, and external crosslinking over various synthesis parameters – residence time, substrate concentration, reagent ratio, and temperature. The space-time-yield (STY) values, a key parameter for productivity rates, of flow synthesis were 32 – 117 folds higher than batch reactions. We observed that flow synthesis could create additional microporosity in internally crosslinked HCPs by limiting reaction rates. This consequently enhanced CO2/N2 selectivity 298 K by 10-folds when compared to HCPs produced in batch reactions. Outcomes from this work could potentially contribute towards high productivity scale up manufacturing of HCPs for post-carbon capture. Publisher PDF

Non-invasive Raman spectroscopy enables in situ monitoring of both solid and solution species in metal–organic framework synthesis. Kinetics derived by this comparably cheaper and accessible technique agree with reported synchrotron diffraction data.

AbstractNative Scottish wood samples were investigated as potential, locally sourced, raw materials for biochar production. Screening experiments identified pure softwood as the preferable feedstock. Influence of operational parameters, i.e. activating gas flow rate (CO2), heating ramp rate and contact time on final biochar characteristics, was investigated using design of experiments. Surface area and biochar yield were selected as response variables. Minitab was used to define experimental run conditions and suggested an optimal output at 60 min contact time and 15 °C/min ramp rate for maximum responses. The highest surface area (764 m2/g) was achieved at 850 °C from softwood, albeit with a low yield of 15%. Under optimised conditions, the observed surface area was 613 m2/g with ~ 18% yield. Pareto charts suggested no influence of gas flow rate on chosen responses, which correlated well with experimental data. Pore structure was a combination of micro- and mesopores with average pore widths of 3–5 nm and an average point of zero charge of 7.40 ± 0.02. Proximate analysis showed an increase in fixed carbon content from 20%, in the feedstock, to 80%, in the optimised biochar. Morphological analysis showed a layered carbon structure in the biochars. The results show the significance of the selected feedstock as a potential source of biochar material and the relevance of interplay of operational variables in biochar development and their final characteristics.

Biochar production from sustainable materials through pyrolysis remains a key area of research, where additional value can be gained by understanding the influence of initial operating parameters to create optimised carbon products with different characteristics. In this study, native Scottish wood samples were used to produce biochars. Softwood and hardwood samples were investigated to determine feedstock importance, with a focus on the influence of process conditions on the final characteristics of biochars. Screening experiments helped to determine that the softwood feedstock resulted in enhanced product characteristics and identified the optimal pyrolysis temperature. A design of experiments approach was used to scope process variables for softwood feedstock: contact time with activating agent, gas flowrate, and influence of ramp rate during pyrolysis were studied. The response variables were product yield and biochar surface area. As expected, product yield decreased with increasing pyrolysis temperature, and increased ramp rates decreased biochar yield. Pore structure was a combination of micro- and mesopores, and high gas flowrate and pyrolysis temperature produced biochars with the greatest surface areas, while morphological analysis suggests a layered carbon structure. Contact angle analysis suggested hydrophilicity, suggesting compatibility with aqueous media, while a neutral surface charge demonstrates easy application in drinking water treatment systems. The results show the potential of parameter optimisation and insight into the interplay of these variables in biochar development, with characteristics that can be tailored to a range of applications.

Recently, we presented a detailed and systematic molecular simulation study of the effect of point charges on adsorption of carbon dioxide and water in a series of typical MOF materials [1]. Unfortunately, we have since detected a mistake in one of the input files pertaining to water adsorption isotherm simulations—concretely, the structure of the water molecule was modelled as linear instead of obeying the correct H-O-H angle of 109.47o for the SPC/E model [2]. As we later found out, this led to a significant underestimation of the amount adsorbed in all water isotherms reported in our original paper, although the relative differences between isotherms obtained using different charge sets are qualitatively the same. We have repeated all the water adsorption simulations, and report the new results here in graphical format. With the exception of a few minor statements, which we also correct below, the conclusions of the original work remain unchanged.

A series of malonic acid treated camelthorn (MATC) sorbents were produced via the reaction of camelthorn biomass with malonic acid, and factors affecting the extent of modification were investigated, including malonic acid concentration, dehydration time and temperature. The optimum sorbent, by carboxylic acid content, was subsequently characterised for surface charge behaviour (pHPZC), surface chemical functionalities (FTIR), morphological structure (SEM), and available surface area. The sorbent was subsequently utilised for adsorption of Cd(II) ions from aqueous media, and parameters influencing adsorption at 30 °C, such as sorbent dose, initial solution pH, exposure time, metal concentration, were investigated. Isothermal analyses were performed using eight models, including two and three parameter equations, with appropriateness of fit assessed via non-linear regression analysis. The adsorption data indicated that the Langmuir model gives the most appropriate fit to experimental curves, with the models ordered as Langmuir > Hill > Toth > Sips > Jossens > Khan > Redlich-Peterson > Freundlich. The highest uptake (qmax) of 582.6 mg g−1was determined at pH 6. The Freundlich constants, KFand n, at 30 °C were found to be 24.94 mg g−1and 2.33, respectively. The value of n (2.33), being in the range 0–10, indicates that adsorption of Cd(II) ions onto malonic acid treated camelthorn biomass is favourable. Evaluation of a series of kinetic models, allowed elucidation of the adsorption mechanism, as a pseudo-second order model gave the most appropriate fit, indicating that chemisorption processes are involved. Cd(II) ions adsorption onto MATC is enhanced by a higher level of active surface sites but was show to be independent of surface area. The work presented here indicates that this sorbent offers effective adsorption potential for Cd(II) ions from water, with potential in wastewater processing.

Microcrystalline cellulose (MCC) has been utilized as an adsorbent material for the removal of Pb(II) ions from aqueous solution after treatment with 1,2,3,4-butanetetracarboxylic acid (BTCA) at elevated temperature to obtain MMCC. The resulting adsorbent was characterized for point of zero point charge (pHZPC), estimation of carboxyl content, Fourier transform infrared spectroscopy (FT-IR), scan electron microscopy (SEM), and textural properties, including surface area, and subsequently utilized for the removal of Pb(II) ions from aqueous solution. The adsorption process was probed by investigating the effect of adsorbent dose, pH of solution, temperature, agitation time, and Pb(II) ion concentration. The results showed successful functionalization of MCC using BTCA, significantly improved the binding properties of the adsorbent towards Pb(II) ions. Isothermal adsorption data was analyzed using Langmuir, Freundlich and Temkin models, evaluated via nonlinear regression analysis. The maximum adsorption capacity was found to be 1155 mg/g (at pH 5 and 30 °C) from Langmuir theory, and appears independent of surface area. The Freundlich model was found to provide the best fit and the constant n was determined to be 2.69, indicating that adsorption of Pb(II) ions onto MMCC is favorable. Kinetic modelling showed good agreement for the pseudo-second order kinetic model, supporting the theory that chemisorption is involved in the adsorption process, which is promoted by a high density of active sites. Thermodynamic analysis showed that the adsorption of Pb(II) ions onto MMCC was endothermic and nonspontaneous; hence, MMCC offers an effective method of Pb(II) ion removal from aqueous solutions, with potential for water remediation processes.

Mercury is a persistent, heavy metal present in watercourses, and this paper presents the synthesis of a new, low-cost sorbent, based on wood pulp, for the targeted removal of Hg (II) from aqueous solutions. Carbamoylethylated wood pulp sorbents were obtained from the reaction of wood pulp with acrylamide, in basic media, to produce a suite of materials with varying nitrogen concentration (0.251.51%). Batch sorption techniques were used to determine the sorption capacity of each sorbent for Hg (II), as a function of pH, contact time, as well as sorbate and sorbent concentrations. The samples were evaluated for bulk and surface chemistry (nitrogen concentration and FTIR) as well as surface morphology and textural properties (SEM and surface area measurements). Sorption analysis via Langmuir, Freundlich and Temkin models, showed that the data were best represented by the Temkin isotherm model suggesting influence from surface heterogeneity in the adsorption process. Langmuir analysis provides an indication of the maximum sorption uptake at 787.6 mg g−1, while Freundlich analysis shows the sorption process to be favourable but with some slight suppression at low concentrations. The results indicate the importance of nitrogen concentration and corresponding sorption capacity in Hg (II) sorption kinetics and are consistent with the recovery rates observed. Sorption tests demonstrate that these sorbents have remarkable potential, which is validated through 39% removal of Hg (II) from aqueous solution, and modelling of the kinetic data showed that the system closely flows a pseudo-second-order kinetic model.

Camelthorn, a desert plant, has been utilized as an adsorbent material for the extraction of Hg(II) ions from aqueous solution after grafting with acrylonitrile followed by amination with hydroxylamine hydrochloride in basic medium to obtain aminated hydroximoyl camelthorn (AHCT). AHCT were found to exhibit excellent adsorption capacity over a wide range of Hg(II) concentration. The surface functional groups and morphology of AHCT were determined. The influences of time (0–60 min), pH (2–6), and dose (0.3–8 g/L) were also evaluated. The adsorption data were analyzed using the Langmuit, Freundlich and Temkin tr models at 30 °C using nonlinear regression analysis. The maximum adsorption capacity (qmax) of Hg(II) onto AHCT was 272.9 mg/g at an initial pH of 6 and a temperature of 30 °C and the Freundlich constants, KF and n, at 30 °C were found to be 25.47 mg/g and 3.2, respectively. The value of n (3.2), which being in the range 0–10 indicate that adsorption of Hg(II) ions onto AHCT is favorable. Various kinetics models including the pseudo-first-order, pseudo-second-order and intraparticle diffusion models have been applied to the experimental data to predict the adsorption kinetics. Kinetic study was carried out by varying initial concentration of Hg(II) at constant temperature and it was found that pseudo-second-order rate equation was better obeyed than pseudo-first-order and intraparticle diffusion supporting that chemisorption process was involved. The examination of R2 values and error analysis method (ARE) showed that the Langmuir model provide the best fit to experimental data than other isotherms and follow the following order: Langmuir > Freundlich > Temkin. The results revealed that the AHCT-Hg(II) ions adsorption system was promoted by the high density of active sites and the adsorption process is independent of the adsorbent surface area. Consequently, AHCT residues can offer an effective method of Hg (II) ion removal from aqueous solutions, demonstrating its potential role in water remediation processes.

Sorptive selectivity of melamine–resorcinol–formaldehyde xerogels, towards CO2, CH4, N2 and H2, is reported, where all systems demonstrate potential for selective adsorption of CO2 from corresponding binary gas mixtures. Selected gas mixtures represent important gas separation applications found in industry, i.e. CO2 removal from power plant flue gases (CO2–N2), sour gas sweetening (CO2–CH4), and separation of species in the water–gas shift reaction (CO2–H2). All materials tested exhibit microporous character, enhancing adsorption of small molecules, however, it is the inclusion of a nitrogen-rich material into the gel matrix that results in enhanced selectivities for these systems. Despite the porous character of the gels, under the test conditions used to simulate industrial parameters, all three balance gases, i.e. H2, N2 and CH4, showed low affinities for the xerogels, while CO2 adsorption was notably higher and increased with the inclusion and increased concentration of melamine. Ideal adsorbed solution theory was used to demonstrate significant differences in adsorption uptake, especially for CO2–CH4, and high selectivities for CO2 over N2. In all cases, selected xerogels exhibited industrially relevant adsorption timescales for CO2 over competitor gases, demonstrating the potential of these materials for the selective adsorption of CO2 from process streams.

Marabu (Dichrostachys cinerea) from Cuba and aspen (Populus tremula) from Britain are two rosid angiosperms that grow easily, as a weed and as a phytoremediator, respectively. As part of scientific efforts to valorise these species, their barks and woods were pyrolysed at 350, 450, 550 and 650 °C, and the resulting biochars were characterised to determine the potential of the products for particular applications. Percentage carbon composition of the biochars generally increased with pyrolysis temperature, giving biochars with highest carbon contents at 650 °C. Biochars produced from the core marabu and aspen wood sections had higher carbon contents (up to 85%) and BET surface areas (up to 381 m2g−1) than those produced from the barks. The biochar porous structures were predominantly mesoporous, while micropores were developed in marabu biochars produced at 650 °C and aspen biochars produced above 550 °C. Chemical and thermal activation of marabu carbon greatly enhanced its adsorption capacity for metaldehyde, a molluscicide that has been detected frequently in UK natural waters above the recommended EU limit.

Microcrystalline cellulose (MCC) was modified with 1, 2, 3, 4-butanetetracarboxylic acid (BTCA) to obtain the adsorbent material named treated microcrystalline cellulose (TMCC), which was characterized for point of zero charge (pHZPC), estimation of carboxyl group content and surface group moieties, surface morphology and textural properties. Application of TMCC for the removal of Hg(II) ions from aqueous solution was studied with respect to carboxyl group content, and process parameters, including adsorbent dose, initial solution pH, temperature, contact time, and Hg(II) ion concentration, to provide information about the adsorption mechanism. Isothermal adsorption data were analysed using a range of two and three parameter adsorption models, with the level of fit determined using nonlinear regression analysis. The maximum adsorption capacity under optimised conditions was determined using Langmuir analysis and found to be 1140 mg/g, and Freundlich analysis showed that adsorption of Hg(II) ions onto TMCC is favourable. The kinetic results using a range of models, showed that a pseudo-second order kinetic model was most appropriate for the data obtained, which indicates that the process involves chemisorption. The results obtained show TMCC to have a high affinity for Hg(II) ions from aqueous media, which suggests that these materials may have potential for application in water treatment systems.

Resorcinol–formaldehyde (RF) gels are porous materials synthesized via a sol–gel reaction and subsequently dried, producing structures with high surface areas and low densities—properties that are highly attractive for use in various applications. The RF gel reaction takes place in the presence of a catalyst, either acidic or basic in nature, the concentration of which significantly impacts final gel properties. The full extent of the catalyst’s role, however, has been subject to debate, with the general consensus within the field being that it is simply a pH-adjuster. The work presented here explores this theory, in addition to other theories postulated in the literature, through the synthesis and analysis of RF gels catalysed by mixtures of relevant compounds with varying concentrations. The relationship between catalyst concentration and initial solution pH is decoupled, and the individual roles of both the cation and the anion within the catalyst are investigated. The results presented here point towards the significance of the metal cation within the RF gel reaction, with similar structural properties observed for gels synthesized at constant Na+ concentrations, regardless of the initial solution pH. Furthermore, through the use of alternative cations and anions within catalyst compounds, the potential effects of ions on the stabilization of macromolecules in solution are explored, the results of which suggest a ‘Hofmeister-like’ series could be applicable within the catalysis of RF gel reactions.

Despite their extensive and decade-long application in wastewater treatment, activated carbon remains one of the most viable adsorbents, with substantive practical application, due to their high pollutant binding capacity. In this study, commercially available activated charcoal was applied in the uptake of aqueous cadmium [Cd(II)] ion. The effect of some process variables on the Cd (II) uptake was investigated via batch mode. Furthermore, the adsorbents’ surface charge (pHPZC), surface morphology (using SEM) and available surface functional groups (using FTIR) were explained. The pH dependence of the present adsorption system was revealed, while the optimum pH was recorded at pH 5.0. Similarly, the Cd (II) uptake (mg/g) decreased with increasing adsorbent dosage due to possible active sites clogging, overcrowding and interference. Furthermore, the isothermal and kinetics analyses of the experimental data, which were aptly validated using the hybrid error model, respectively depicted the Langmuir isotherm and pseudo-second-order kinetic model as the best fit. A Langmuir adsorption capacity of 682.5 mg g−1 was also recorded in the study. Consequently, the present adsorption system was characterized by an equilibrium timeframe of industrial practicability; hence, the adsorbent was successfully applied for the aqueous Cd (II) uptake.

There has been significant research interest invested into the study of the formation and properties of porous organic materials, due to their widespread applications. However, present models in the literature do not fully explain the observations made for these systems, therefore, this work presents a model developed to fully capture growth from the monomeric species present in the initial stages of the gelation composition. In this work, we employ a two-dimensional lattice-based kinetic Monte Carlo model to investigate how growth processes impact the structural properties of model gels. Experimentally, gel growth is primarily controlled through catalyst concentration, which determines the density of species that are activated for rapid growth, and solids concentration; our model captures both of these dependencies. Increasing both solids content and percentage of activated monomers leads to a higher ratio of closed porosity, and higher values of accessible surface area with increasing level of activation. The generated structures are analysed for their fractal properties using a correlation dimension. Increasing both solids content and percentage of activated species leads to an increase in correlation dimension, which plateaus at a value of 2, independent of catalyst concentration, suggesting little structural change at high solid loadings, over 50%. The Hurst exponent of a random walker diffusing in the accessible pores shows the opposite trend, varying from 1/2 for unconstrained diffusion and reducing to 1/3; for diffusion through the pore network at the threshold of percolation. These characteristics support visual observations of increasing complexity and tortuosity of pore structures in the model cluster structures. The implications of these results, for the design of porous structures tailored to particular applications, are discussed.

Selected melamine–resorcinol–formaldehyde (MRF) xerogels have been synthesized and analyzed to determine the influence of nitrogen (N) incorporated into the gel structure and resorcinol-to-catalyst (sodium carbonate) and resorcinol-to-formaldehyde molar ratios. The aforementioned factors were varied, and their effect on gel properties was characterized, allowing for a better understanding of how gel characteristics can be tailored and their impact on gel performance. MRF gels, produced in this study, were characterized using volumetric and gravimetric analyses to determine porous structure and quantify CO2 capture capacities and kinetics, allowing determination of heats of adsorption and activation energies for CO2. MRF10_200_0.25 has exhibited the largest CO2 capacity (1.8 mmol/g at 0 °C) of the sample tested. Thermal stability was tested by proximate analysis, and MRF xerogels exhibited high thermal stability; however, it was found that volatile matter increases as [M] increases, particularly for [M] 20%w/w and higher. Working capacity was determined from a series of cycling studies, and capacities of 0.55, 0.58, and 0.56 mmol/g at 60 °C were observed for [M] of 10, 20, and 30%w/w, respectively. The measured heat of adsorption showed that incorporation of nitrogen functionalities results in a low energy penalty, demonstrating that the adsorption mechanism is still driven by physical forces. The results obtained indicate that the family of materials studied here offer potential routes for carbon capture materials, through a combination of micropore structure development and incorporation of favorable Lewis acid–base interactions.

Assessing the efficacy of specific porous materials for use in various applications has been a central focus for many experimental studies over the years, with a view to altering the material properties according to the desired characteristics. The application potential for one such class of nanoporous materials - organic resorcinol-formaldehyde (RF) gels - is of particular interest, due to their attractive and adjustable properties. In this work, we simulate adsorption analysis using lattice-based mean field theory, both in individual pores and within three-dimensional porous materials generated from a kinetic Monte Carlo cluster aggregation model. We investigate the impacts of varying pore size and geometry on the adsorptive behavior, with results agreeing with those previously postulated in the literature. The adsorption analysis is carried out for porous materials simulated with varying catalyst concentrations and solids contents, allowing their structural properties to be assessed from resulting isotherms and the adsorption and desorption processes visualized using density color maps. Isotherm analysis indicated that both low catalyst concentrations and low solids contents resulted in structures with open transport pores that were larger in width, while high catalyst concentrations and solids contents resulted in structures with bottleneck pores that were narrower. We present results from both the simulated isotherms and pore size analysis distributions, in addition to results from RF gels synthesized in the lab and analyzed experimentally, with significant similarities observed between the two. Not only do the results of this comparison validate the kinetic Monte Carlo model's ability to successfully capture the formation of RF gels under varying synthesis parameters, but they also show significant promise for the tailoring of material properties in an efficient and computationally inexpensive manner - something which would be pivotal in realizing their full application potential, and could be applied to other porous materials whose formation mechanism operates under similar principles.

The metal–organic framework (Me2NH2)2[Cd(NO2BDC)2] (SHF-81) comprises flattened tetrahedral Cd(O2CR)42- nodes, in which Cd(II) centres are linked via NO2BDC2- ligands (2-nitrobenzene-1,4-dicarboxylate) to give a doubly interpenetrated anionic network, with charge balanced by two Me2NH2+ cations per Cd centre resident in the pores. The study establishes that this is a twinned α-quartz-type structure (trigonal, space group P3x21, x = 1 or 2), although very close to the higher symmetry β-quartz arrangement (hexagonal, P6x22, x = 2 or 4) in its as-synthesised solvated form [Cd(NO2BDC)2]·2DMF·0.5H2O (SHF-81-DMF). The activated MOF exhibits very little N2 uptake at 77 K, but shows significant CO2 uptake at 273–298 K with an isosteric enthalpy of adsorption (ΔHads) at zero coverage of -27.4 kJ mol-1 determined for the MOF directly activated from SHF-81-DMF. A series of in situ diffraction experiments, both single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD), reveal that the MOF is flexible and exhibits breathing behaviour with observed changes as large as 12% in the a- and b-axes (|Δa|, |Δb| < 1.8 °A) and 5.5% in the c-axis (|Δc| < 0.7 °A). Both the solvated SHF-81-DMF and activated/desolvated SHF-81forms of the MOF exhibit linear negative thermal expansion (NTE), in which pores that run parallel to the c-axis expand in diameter (a- and b-axis) while contracting in length (c-axis) upon increasing temperature. Adsorption of CO2 gas at 298 K also results in linear negative expansion (Δa, Δb > 0; Δc < 0; ΔV > 0). The largest change in dimensions is observed during activation/desolvation from SHF-81-DMF to SHF-81 (Δa, Δb < 0; Δc > 0; ΔV < 0). Collectively the nine in situ diffraction experiments conducted suggest the breathing behaviour is continuous, although individual desolvation and adsorption experiments do not rule out the possibility of a gating or step at intermediate geometries that is coupled with continuous dynamic behaviour towards the extremities of the breathing amplitude.

Online teaching and learning opens up great opportunities, particularly in terms of widening access to education, but also poses important challenges related to delivery, student engagement, adapting contents, and ensuring reliability of assessment. Some of these challenges assume particular relevance in engineering degrees, due to their strong practical dimension, the connection to industrial practice, and the need for programme accreditation. This chapter focuses on the example of the Chemical Engineering Distance Learning degree at the University of Strathclyde, describing its decade-long transformation from a mainly correspondence-based course to a fully online programme. The main challenges faced by course directors and teaching staff are identified, and the response to those challenges is critically discussed. Finally, a reflection is presented on the future of distance learning programmes in the context of expected developments enabled by online technologies, artificial intelligence, and collection of rich datasets on learner engagement and development.

The metal-organic framework (Me

Calligonum crinitum, a desert plant, was used as a natural adsorbent for the removal of Pb(II) ions from aqueous solutions. The sorption capacity of the sorbent was investigated through batch adsorption, as a function of contact time, metal ion concentration, and pH. The surface chemistry of the sorbent was probed using Fourier transform infrared spectroscopy, allowing an understanding of the key functionalities involved in binding the Pb(II) ions to the sorbent. Textural characteristics, including surface area and pore volume, showed higher surface areas relative to other natural adsorbents previously reported. Surface morphological analysis, observed via Scanning Electron Microscopy images and Energy-Dispersive X-Ray analysis, confirmed adsorption of Pb(II) ions, up to 71% on the surface of calligonum crinitum. Isothermal analysis, using Langmuir, Freundlich and Temkin models with nonlinear regression, showedthe Langmuir model to best represent adsorption within this system, yielding a maximum adsorption capacity of 337 mg g−1 (pH 5.5, 30 °C). The optimum conditions of adsorption was pH, 5.5; adsorbent concentration, 0.3 g/l, contact time, 20 min at 30 °C. The Freundlich constant of

An aminated acrylic fiber waste has been utilized as an adsorbent material for the removal of Cd(II) ions from aqueous solution after treatment of acrylic fiber waste with hydroxylamine hydrochloride under basic conditions, and characterized for surface chemistry, surface morphology and textural properties. The ability of this sorbent to adsorb Cd(II) ions was examined via batch adsorption methods, studying the effect of pH, sorbent and sorbate concentrations, as well as contact time. Results obtained confirm that this sorbent was effective for Cd(II) ion adsorption, with uptakes promoted by high active site density, however, the adsorption process is independent of sorbent surface area. The values obtained exceed those previously reported within the literature. Isotherm analysis using arrange of two- and three- parameter models, evaluated using non-linear regression methods with error analysis, showed that the Langmuir isotherm model most appropriately described the experimental data obtained, indicating mono layer adsorption occurs. Kinetic analysis using arrange of models in their non-linear forms provided mechanistic information, showing that pseudo -second-order behavior is involved. The synthesized aminated acrylic fiber waste derived sorbents offer significant potential for the removal of Cd(II) ions from aqueous solution through a mechanism of chelation between the electron- donating oxygen-and nitrogen-containing groups in the sorbent and the electron-accepting Cd(II) ions.

Resorcinol (R) and formaldehyde (F) gel synthesis has been well-studied along with alternative reagents. We present the synthesis of formaldehyde-based xerogels using chemically similar s-triazine precursors, with comparison to traditional analogues. The substitution ranges from tri-hydroxyl to tri-amine, with an intermediate species, allowing changing chemistry to be investigated. Each molecule (X) offers different acid/base properties, known to influence gel formation, as well as differences in crosslinking potential. Varying X/F ratios were selected to recreate the stoichiometry used in RF systems, where one represented higher F to match the increased reaction sites of the additives. X/C ratios were selected to probe different catalyst (C) ratios, while working within the range likely to produce viable gels. Results obtained show little impact for ammeline as an additive due to its similarity to resorcinol (activation sites and pKa), while melamine and cyanuric acid show differing behavior depending on the level of addition. Low concentrations show melamine to have the most impact due to increased activation and competition for formaldehyde, while at high concentrations, cyanuric acid is shown to have the greatest impact as it creates a more acidic environment, which diminishes textural character, possibly attributable to larger clusters and/or weaker cross-linking of the system.

A metal organic framework Cu(tpt)BF4&middot, &frac34, H2O was synthesized as a potential carbon capture material, with the aim being to exploit the Lewis base interaction of the incorporated ligand functionalities with acidic gas. The material displays high thermal stability but an exceptionally low surface area, however, this contrasts starkly with its ability to capture carbon dioxide, demonstrating significant activated diffusion within the framework. The full characterization of the material shows a robust structure, where the CO2 sorption is 120% greater than current industrial methods using liquid amine solutions, the thermal energy required for sorbent regeneration is reduced by 65%, indicating the true industrial potential of the synthesized material.

The facile modification of pinewood sawdust, with maleic acid, to produce a sorbent aimed at metal ion adsorption, was tested via the batch adsorption of Cd(II) ions from aqueous solution. The sorbent was characterized for the pH of zero point charge (pHZPC), spectroscopic evaluation of the surface functionalization, structural and morphological features. Factors affecting adsorption behavior, such as adsorbent dose, pH of solution, contact time and Cd(II) ion concentration were investigated. Results obtained show the adsorption rate to be comparatively fast, with equilibrium achieved after ∼35 min. Subsequent analysis, showed Langmuirian behavior and a monolayer adsorption capacity of 180.4 mg g−1, at pH 6; while data derived from two-parameter and three-parameter isotherm models was evaluated using non-linear regression methods, with error analysis, to determine the most appropriate model and allow prediction of optimum parameters. The Sips isotherm model proved the most appropriate in describing the experimental data obtained in the study; with a low level of heterogeneity in the adsorption sites occupied suggesting the interaction of the metal ions is preferential with the added carboxylate moieties only. Additionally, the rate of adsorption was analysed using a range of kinetic models (pseudo-first-order, pseudo-second-order, Bangham and Elovich) in their non-linear forms to provide insight into the adsorption mechanism and showing pseudo-second order behavior is observed, indicating two processes are key in the adsorption process, likely diffusion to the surface and subsequent adsorption on the carboxylate moieties incorporated by chemical modification. In conclusion, the sorbent produced in this study offers high potential for the removal of Cd(II) ions from aqueous solution due to the carboxylic functionalities incorporated into the material, which is optimized by solution pH and adsorbent dose.

The interactions between metal–organic frameworks (MOFs) and adsorbates have been increasingly predicted and studied by computer simulations, particularly by Grand-Canonical Monte Carlo (GCMC), as this method enables comparing the results with experimental data and also provides a degree of molecular level detail that is difficult to obtain in experiments. The assignment of atomic point charges to each atom of the framework is essential for modelling Coulombic interactions between the MOF and the adsorbate. Such interactions are important in adsorption of polar gases like water or carbon dioxide, both of which are central in carbon capture processes. The aim of this work is to systematically investigate the effect of varying atomic point charges on adsorption isotherm predictions, identify the underlying trends, and based on this knowledge to improve existing models in order to increase the accuracy of gas adsorption prediction in MOFs. Adsorption isotherms for CO2 and water in several MOFs were generated with GCMC, using the same computational parameters for each material except framework point charge sets that were obtained through a wide range of computational approaches. We carried out this work for 6 widely studied MOFs; IRMOF-1, MIL-47, UiO-66, CuBTC, Co-MOF-74 and SIFSIX-2-Cu-I. We included both MOFs with and without open metal sites (OMS), specifically to investigate whether this property affects the predicted adsorption behaviour. Our results show that point charges obtained from quantum mechanical calculations on fully periodic structures are generally more consistent and reliable than those obtained from either cluster-based QM calculations or semi-empirical approaches. Furthermore, adsorption in MOFs that contain OMS is much more sensitive to the point charge values, with particularly large variability being observed for water adsorption in such MOFs. This suggests that particular care must be taken when simulating adsorption of polar molecules in MOFs with open metal sites to ensure that accurate results are obtained.

Formaldehyde forms a variety of hydrated and methoxylated species when reacted with water and methanol. Vibrational spectroscopy has been deployed for both remote and in situ sensing of formaldehyde species and it can be a useful tool for process development, monitoring and control at both laboratory and industrial scale, as well as for environmental, atmospheric and space monitoring. While IR and Raman spectroscopic studies of formaldehyde species in solid, liquid or gas phases have been reported, assignments of vibrational frequencies of relevant species in previous literature have been contradictory and incomplete. In this work we report IR and Raman spectra for formaldehyde-water-methanol solutions across a wide range of formaldehyde concentrations and solvent compositions. We present an analysis of vibrational spectra of formaldehyde-water-methanol systems using a combination of experimental measurements and gas phase quantum mechanical density functional theory simulations. For the first time, we explicitly consider spectra of oligomeric mixtures of formaldehyde species in relation to spectra of specific representative hydrated and methoxylated species and we resolve some previously reported contradictions in assignments of vibrational frequencies for formaldehyde systems.

Integrated learning makes use of group work to develop students’ professional competencies in tandem with their transferable skills. This paper looks at the skills required to undertake a fourth year chemical engineering “capstone design project” (Design) and the skills developed therein. Staff and students were surveyed about their perceived skills abilities, both before and after the project; the results of which showed agreement as to the skills necessary to undertake Design: these were grouped under personal effectiveness skills, communication skills or research skills. Students described a number of extra-curricular activities that contributed to skills development but sometimes failed to appreciate their transference to academic arenas. The surveyed students indicated that their confidence in all skills areas was increased by Design: but there were instances where some individual sub-set devaluing occurred. There is a link between experiential practice, predominantly as a result of producing assessed components, and high skills confidence; hence, it is recommended that students are encouraged to reflect on their project experience and that integrated learning be promoted to develop all skills effectively.

The herbicide terbuthylazine (TBA) has displaced atrazine in most of EU countries, becoming one of the most regularly used pesticides and, therefore, frequently detected in natural waters. The affinity of TBA for soil organic matter suggests prolonged contamination; degradation leads to the release of the metabolite desethylterbuthylazine (DET), which has higher water solubility and binds more weakly to organic matter compared to the parent compound, resulting in higher associated risk for contamination of groundwater resources. Additionally, TBA and DET are chemicals of emerging concern because of their persistence and toxicity towards aquatic organisms; moreover, they are known to have significant endocrine disruption capacity to wildlife and humans. Conventional treatments applied during drinking water production do not lead to the complete removal of these chemicals; activated carbon provides the greatest efficiency, whereas ozonation can generate by-products with comparable oestrogenic activity to atrazine. Hydrogen peroxide alone is ineffective to degrade TBA, while UV/H2O2 advanced oxidation and photocatalysis are the most effective processes for oxidation of TBA. It has been determined that direct photolysis gives the highest degradation efficiency of all UV/H2O2 treatments, while most of the photocatalytic degradation is attributed to OH radicals, and TiO2 solar-photocatalytic ozonation can lead to almost complete TBA removal in ∼30 min. Constructed wetlands provide a valuable buffer capacity, protecting downstream surface waters from contaminated runoff. TBA and DET occurrence are summarized and removal techniques are critically evaluated and compared, to provide the reader with a comprehensive guide to state-of-the-art TBA removal and potential future treatments.

Resorcinol-formaldehyde (RF) xerogels are organic materials have been widely studied due to their industrially relevant characteristics, through which, RF gels have significant potential to be tailored to specific applications. Xerogel properties have been tailored, within this study, by altering the synthesis procedure with a focus on monomer concentrations, catalyst to monomer ratio, and the introduction of a nitrogen-rich precursor, thereby incorporating nitrogen into the structure to additionally affect the chemical properties of the final gel. Melamine (M) is used as the source of nitrogen, partially replacing the resorcinol (R) typically used, and resulting in a melamine-resorcinol-formaldehyde (MRF) gel; synthesis was facilitated by a sodium carbonate catalyst (C), as often used in RF gel production. R/C and R/F molar ratios, and M concentration ([M]), were chosen as parameters to study in-depth, as they have previously been shown to markedly influence sol-gel formation. The MRF gels produced were subsequently characterized to determine porous structure and chemical functionality. The results indicate that, texturally, increasing [M] produces a similar effect as increasing R/C values: increasing pore size, while decreasing surface area. Pore volume tends to increase when R/C or M increase individually but pore volume and surface area decrease drastically when both variables increase concurrently. Microporosity also tends to increase as R/C decreases, and as the concentration of M is decreased. Altering the gel matrix, by replacing M for R, results in a weakening of the gel structure, as the bridges formed during curing are reduced in quantity, which indicates a maximum level of substitution that can occur within these materials. Combined, these results suggest that nitrogen can be successfully incorporated into organic gel structures but that the interplay between process variables is crucial in determining final gel characteristics for specific applications.

Resorcinol-formaldehyde gels offer a range of properties that can be exploited in a variety of applications, but better understanding of gel formation mechanisms is needed to enable rational control and optimisation of the physico-chemical characteristics of these materials. Our previous studies have focussed on investigating the formation pathways of these gels, using nuclear magnetic resonance and dynamic light-scattering techniques, as well as evaluating their final physical and chemical properties, via sorption and spectroscopic methods. Nuclear magnetic resonance has been used over the years to probe the chemical species formed during resorcinol-formaldehyde gel polymerisation, but the technique typically involves the prior addition of deuterium oxide to provide a deuterium lock for NMR measurements. However, the effect of deuterium oxide to resorcinol-formaldehyde systems is currently unknown, although the substitution of water by deuterium oxide has been previously reported to alter the chemical and physical properties of reacting systems. In this work we examine the effect of adding deuterium oxide to resorcinol-formaldehyde sol-gel synthesis at different dilution levels and the impact that this addition has on the final characteristics of the synthesised gels, in order to assess the validity of using NMR with a deuterium lock for the investigation of polymerisation mechanism in resorcinol-formaldehyde sol-gel processes.

In recent years, the presence of Endocrine Disrupting Chemicals (EDCs) in wastewater discharges from agricultural and industrial sources, [1] fresh- and estuarine-waters, as well as soils, has been reported in the literature. [2] Studies of adverse changes in wildlife, linked to environmental exposure to these substances, and the suggestion that humans could also be at similar risk of adverse health effects, [3-5] have raised concern for urgent action to understand and reduce such risks. 3,4-Dichloroaniline (3,4-DCA) has been recognized as an EDC, with regards to endocrine disruption data for both wildlife populations and human health. [5] 3,4-DCA is present in the environment as a product of the biodegradation of phenylurea and phenylcarbamate pesticides [6,7] ; furthermore, it can be introduced from industrial and municipal wastewater that is insufficiently purified, or via accidental spills. [8-10] Increasing concentrations of 3,4-DCA in soil and water are the result of its high persistence and accumulation, as well as its low biodegradability. [11,12] Hence, remediation techniques require in-depth study, especially when considering the low removal achieved by traditional activated sludge treatments, and the generation of carcinogenic trihalomethanes as a consequence of the chlorine oxidation methods frequently used in drinking water plants. [13] Fe0/H2O2 systems, photodegradation using doped TiO2, and the use of dielectric barrier discharge reactors, seem to be the most promising techniques for the removal of 3,4-DCA from water.

Very few studies have investigated the adsorption performance of hydrophobic and hydrophilic silicas with dissolved organics in water, which is a required final step during produced water treatment. The cost of functionalization also hinders the use of hydrophobic materials as sorbents. Novel hydrophilic silicas, prepared at low temperature and ambient pressure, were characterised by SEM, FTIR and BET analysis, and studied for the adsorption of aqueous phase organic compounds at concentrations below their solubility limits. Adsorption capacities were found to be up to 264 mg/g for benzene and 78.8 mg/g for toluene. Direct comparison is made with the analogous hydrophobic version of one of the silica materials, demonstrating comparable uptakes for benzene concentrations lower than 50 mg/L. This finding supports the hypothesis that, at very low aqueous phase organic concentrations, hydrophobicization has no discernible effect on access of the pollutants to the internal porosity of the material.

The adsorption capacities of a novel amorphous silica and silica xerogels for aromatic compounds were investigated using microcolumn rapid breakthrough tests coupled with sequential injection flow-based automated instrumentation in order to evaluate their operative feasibility under conditions typically used in water treatment facilities. Extraction columns were fabricated using stereolithographic 3D printing. Sorbent reusability was also investigated using automated flow-based techniques. Benzene was selected as the target dissolved organic compound usually present in produced waters from the oil and gas sector, continuously increasing. 3,4-Dichloroaniline (3,4-DCA) was selected as part of the endocrine disrupting chemicals, which are becoming a source of major concern for human and wildlife toxicity. Novel amorphous silicas were synthesized at low temperature and under ambient pressure from a sodium metasilicate precursor and were subjected to postsynthetic methylation. Silica xerogels were prepared via acid catalysis of a sodium metasilicate solution and functionalized with trimethylchlorosilane at low temperature and under ambient pressure. The removal efficiency of the silica xerogels tested was found to be equal to or greater than 22.62 mg/g for benzene at a flow rate of 0.6 mL/min, while the uptake of 3,4-DCA was found to be > 4.63 and > 7.17 mg/g, respectively, at flow rates of 1.8 and 0.6 mL/min.

Metal–organic frameworks (MOFs) are well suited as nanoporous materials for applications such as gas storage, catalysis and in medical devices. Literature predominantly covers information on the batch synthesis of MOF-5, however, for an industrially viable product to be formed, bridging the gap to scalable continuous processing is essential. Here, we show that crystals of MOF-5 can be formed in a scalable solvothermal continuous process with a maximum space time yield of nearly 1000 kg m−3 day−1. Analysis of the solid output as a function of time, in conjunction with variation of concentration of the feed supply, shows high purity MOF-5 is produced using a continuous system, with potentially high throughput on scale up. We also show that the output can be increased by increasing the concentration of reactants in the system, albeit resulting in a reduced surface area. The two most common solvents currently used for MOF-5 production are also compared to identify a more economically viable process.

A deeper understanding of the chemistry and physics of growth, aggregation and gelation processes involved in the formation of xerogels is key to providing greater control of the porous characteristics of such materials, increasing the range of applications for which they may be utilised. Time-resolved dynamic light scattering has been used to study the formation of resorcinol-formaldehyde gels in the presence of combinations of Group I (Na and Cs) and Group II (Ca and Ba) metal carbonates. It was found that the combined catalyst composition, including species and times of addition, is crucial in determining the end properties of the xerogels, via its effect on growth of clusters involved in formation of the gel network. Combination materials have textural characteristics within the full gamut offered by each catalyst alone; however, in addition, combination materials which retain the small pores associated with sodium carbonate catalysed xerogels exhibit a narrowing of the pore size distribution, providing an increased pore volume within an application-specific range of pore sizes. We also show evidence of pore size tunability while maintaining ionic strength, which significantly increases the potential of such systems for biological applications.

Tailoring the properties of porous organic materials, such as resorcinol&ndash, formaldehyde gels, for use in various applications has been a central focus for many studies in recent years. In order to achieve effective optimisation for each application, this work aims to assess the impact of the various synthesis parameters on the final textural properties of the gel. Here, the formation of porous organic gels is modelled using a three-dimensional lattice-based Monte Carlo simulation. We model growth from monomer species into the interconnected primary clusters of a gel, and account for varying catalyst concentration and solids content, two parameters proven to control gel properties in experimental work. In addition to analysing the textural properties of the simulated materials, we also explore their fractal properties through correlation dimension and Hurst exponent calculations. The correlation dimension shows that while fractal properties are not typically observed in scattering experiments, they are possible to achieve with sufficiently low solids content and catalyst concentration. Furthermore, fractal properties are also apparent from the analysis of the diffusion path of guest species through the gel&rsquo, s porous network. This model, therefore, provides insight into how porous organic gels can be manufactured with their textural and fractal properties computationally tailored according to the intended application.

This chapter explores the role of problem-based learning (PBL) in facilitating students’ engagement with design components of a chemical engineering degree at the University of Strathclyde (UoS), where students are required to plan and evaluate a manufacturing process. Teaching staff previously identified issues with students’ abilities to deal with open-ended problems in chemical engineering and to accept open-endedness itself, identifying open-endedness as a threshold concept in design. Work was subsequently undertaken to develop appropriate PBL content to address this threshold concept and associated drop-out rates. A longitudinal programme was engineered to support student learning via a dedicated PBL module, enhancing the students; experience. The benefits of such a programme go beyond the students’ academic career and provide significant impact in achieving success in the real world. The chapter presents findings from this work and builds on the use of threshold concepts in PBL, as introduced in the works of Land and Savin-Baden, relating them to the engineering discipline and reporting on the successful incorporation of PBL activities in early years to help students overcome the liminality that results from open-ended working.

Carbonate rock reservoirs comprise approximately 60% of the world’s oil and gas reserves. Complex flow mechanisms and strong adsorption of crude oil on carbonate formation surfaces can reduce hydrocarbon recovery of an oil-wet carbonate reservoir to as low as 10%. Low salinity waterflooding (LSW) has been confirmed as a promising technique to improve the oil recovery factor. However, the principal mechanism underpinning this recovery method is not fully understood, which poses a challenge toward designing the optimal salinity and ionic composition of any injection solution. In general, it is believed that there is more than one mechanism involved in LSW of carbonates; even though wettability alteration toward a more desirable state for oil to be recovered could be the main cause during LSW, how this alteration happens is still the subject of debate. This paper reviews different working conditions of LSW, previous studies, and field observations, alongside the proposed interfacial mechanisms which affect the colloidal interactions at oil–rock–brine interfaces. This paper provides a comprehensive review of studies on LSW in carbonate formation and further analyzes the latest achievements of LSW application in carbonates, which could help to better understand the challenges involved in these complicated multicomponent systems and would potentially benefit the oil production industry.

Flexible metal-organic frameworks (MOFs) are class of porous crystalline materials that show a structural change upon external stimulus. Understanding this behaviour underpins the design of new responsive porous materials that can target specific applications such as gas separation, molecular sensing, catalysis and drug delivery. Most flexible MOFs undergo well-defined crystallographic transitions between open and closed-pore forms known as “breathing”. By contrast, continuous flexible behaviour is rare and detailed characterisation is very limited. Here we report a continuous breathing mechanism that can be followed by single-crystal diffraction in a MOF with a diamondoid network, (Me2NH2)[In(ABDC)2] (ABDC = 2-aminobenzene-1,4-dicarboxylate) (1). The mechanism is highly solvent-dependent and desolvation from different pore-solvent content enables access to two polymorphic desolvated forms with very different pore openings. These two forms exhibit markedly different gas adsorption capacities and different CO2 vs CH4 selectivity. Partial desolvation introduces a gating pressure associated with CO2 adsorption, absent in the desolvated forms, leading to a combination of stepped and continuous breathing of the framework.

Sulfonic acid functionalized mesoporous silicas with various loadings of acid functionality were synthesized, characterized and applied as heterogeneous catalysts for the degradation of metaldehyde, a persistent organic pollutant in water supplies. Nuclear magnetic resonance spectroscopy showed that acetaldehyde was the only by-product of catalytic degradation, and a detailed mechanism is proposed. Kinetic studies revealed that catalyst performance is related to the accessibility of metaldehyde to active sites, such that high sulfonic acid content is undesirable since it reduces pore size, and decreases pore volume and surface area. Acetaldehyde produced via catalytic degradation, was successfully removed via chemisorption on a second mesoporous silica adsorbent modified with amine functionalities. However, limited by the surface condensation reaction mechanism, mesoporous adsorbents are less desirable than macroporous materials, with respect to acetaldehyde removal, hence, a macroporous ion-exchange resin was employed, which showed much superior performance than the amine modified silica, with a maximum capacity up to 441 mg/g. A dual-stage method is proposed to completely remove metaldehyde from drinking water by initial degradation of metaldehyde, using sulfonic acid functionalized mesoporous silica, into a single by-product, acetaldehyde, removed via chemisorption on amine bearing macroporous ion-exchange resin. The results present a promising system for removal of metaldehyde from drinking water supplies, with potential application to other contaminants.