Iron has been used previously in water decontamination, either unsupported or supported on clays, polymers, carbons or ceramics such as silica. However, the reported synthesis procedures are tedious, lengthy (involving various steps), and either utilise or produce toxic chemicals. Herein, the use of a simple, rapid, bio-inspired green synthesis method is reported to prepare, for the first time, a family of iron supported on green nanosilica materials (Fe@GN) to create new technological solutions for water remediation. In particular, Fe@GN were employed for the removal of arsenate ions as a model for potentially toxic elements in aqueous solution. Several characterization techniques were used to study the physical, structural and chemical properties of the new Fe@GN. When evaluated as an adsorption platform for the removal of arsenate ions, Fe@GN exhibited high adsorption capacity (69 mg of As per g of Fe@GN) with superior kinetics (reaching ∼35 mg As per g sorbent per hr) – threefold higher than the highest removal rates reported to date. Moreover, a method was developed to regenerate the Fe@GN allowing for a full recovery and reuse of the adsorbent in subsequent extractions; strongly highlighting the potential technological benefits of these new green materials.

Since being recognised as a potential emissive source, plastics in heritage collections are being investigated to understand the chemical compounds they release and how they might affect the stability of other heritage objects. There is a requirement for non-invasive methods of analyses to identify unknown plastics and the emitted volatiles they generate. Therefore, Tenax-TA sampling tubes were used to collect the emitted volatiles from 41 samples of 9 polymer types of varying formulation, provenance and age. Thermal desorption-gas chromatography coupled with mass spectrometry (TD-GC/MS) has been successfully used to separate and identify the emissions of the 41 samples at 23 °C, after heating to 70 °C and after accelerated degradation.

Adsorbents were synthesized to obtain novel silica nanoparticles with a broad pore-size distribution (herein referred to as USG-41). The material demonstrated fast adsorption rates with highest adsorption capacities following Langmuir adsorption. Kinetic data best fit the intraparticle diffusion model demonstrating a two-step, surface and pore, adsorption process with pore diffusion being the rate determining step. This data provides key evidence of internal pore chelation of dichromate ions by USG-41. In contrast silica adsorbents (SBA-15 and MCM-41) prepared with similar average pore sizes to USG-41, but with narrow pore-size distributions, had lower adsorption capacities and their kinetic date best fit pseudo-second order diffusion models indicating a one-step, surface only, adsorption process. This study clearly demonstrated that pores size distribution, not the surface area or the average pore size, was central to ensure optimum adsorbent performance for removal of Cr (VI) from contaminated water.Graphical abstractHighlights► A new broad pore size distribution mesoporous silicate (USG-41) used to extract Cr (VI) from water. ► The USG-41 demonstrated fast adsorption rates with high adsorption capacities. ► The pore diffusion of Cr (VI) being the rate determining step when USG-41 used. ► FTIR spectra suggested different adsorption behaviors onto silica nanoparticles with different pore size distributions.

This paper demonstrates the use of functionalized meso-silica materials (MCM-41 or SBA-15) as adsorbents for formaldehyde (H2CO) vapor from contaminated air. Additionally new green nanosilica (GNs) materials were prepared via a bioinspired synthesis route and were assessed for removal of H2CO from contaminated indoor air. These exciting new materials were prepared via rapid, 15 min, environmentally friendly synthesis routes avoiding any secondary pollution. They provided an excellent platform for functionalization and extraction of H2CO demonstrating similar performance to the conventional meso-silica materials. To the authors’ knowledge this is the first reported practical application of this material type. Prior to trapping, all materials were functionalized with amino-propyl groups which led to chemisorption of H2CO; removing it permanently from air. No retention of H2CO was achieved with nonfunctionalized material and it was observed that best extraction performance required a dynamic adsorption setup when compared to passive application. These results demonstrate the first application of GNs as potential adsorbents and functionalized meso-silica for use in remediation of air pollution in indoor air.

Speciation and separation of chromium (VI) and chromium (III) from aqueous solutions were investigated using amino-propyl functionalised mesoporous silica (AP-MCM-41) as an adsorbent. The as-synthesised adsorbent was produced following a simple synthesis method at room temperature prior to template removal using microwave digestion. The maximum adsorption capacity at 111.1 mg/g was calculated according to the Langmuir isotherm model, suggesting a 1:1 monolayer adsorption mechanism. Moreover, AP is a simple chelate, yet it can extract Cr (VI) exclusively from solutions containing other mixed metal ions simply by tuning the solution pH. Recovery of Cr (VI) from loaded sorbents is equally easy to perform with 100% extraction efficiencies allowing reuse of the sorbent and recovery of Cr (VI) from aqueous solutions containing a complex mixture of ions. The material would find use in environmental remediation applications, as a selective adsorbent of Cr (VI) or even as a solid-phase extraction stationary phase to remove and pre-concentrate Cr (VI) from aqueous solutions; this study demonstrates enrichment factors of 100 although higher levels are also possible.Graphical abstractHighlights► A new synthesis method has been used for adsorption of Cr (VI) from aqueous solution. ► Selective extraction of Cr (VI) is achieved by simple solution pre-treatment method. ► Ultra high adsorption capacity compared with conventional sorbents. ► The material is easy to regenerate and reuse. ► Very good performance for Cr (VI) preconcentration.

Indoor air can become polluted with VOCs, and understanding the factors which affect adsorption of VOCs from indoor air is important for: (i) the accurate measurement of VOCs, and (ii) to apply mitigation strategies when high analyte concentrations are measured. In this study four VOCs (toluene, ethylbenzene, cumene and dichlorobenzene) were generated as a constant and controlled polluted air stream of VOCs from a dynamic atmospheric chamber. The effects of relative humidity, and sampling flow rate, on adsorption onto Tenax TA and the relatively new silica adsorbents SBA-15 or MCM-41 were studied. Air samples were collected and analyzed by thermal desorption followed by GC/MS. All sorbents were shown to be affected by changing the RH conditions from 25 to 80% RH, and sampling flow rates from 25 to 200 cm3 min−1, even when pollutant concentrations and sampled air volumes remained consistent. Although further work is required to examine the effect of the full RH range on scavenging potential, in this study Tenax TA was shown to provide best performance in high RH conditions whereas silica sorbents were more effective at low RH. Moreover it was shown that to provide accurate measurements in the field (e.g., when humidity conditions are fixed) it is suggested that Tenax TA is the preferred sorbent of choice as the masses of VOCs collected were less affected by changing the sampling flow rates.

A trapping reagent for formaldehyde, based on the pararosaniline reaction, was evaluated as a method of determination of formaldehyde in the aqueous or vapour phase. Collection of formaldehyde vapour relied upon passive diffusion of formaldehyde into the trapping media and quantitative results were obtained without the need for liquid impingers, bubblers or active sampling pumps. Moreover, a novel, hand-held absorption spectrophotometric measurement device was designed to provide on-site, quantitative measurements. It is proposed that the full measurement system devised would be ideally suited to specific sampling applications such as those found in museum enclosures.

Indoor air can become polluted with VOCs, and understanding the factors which affect adsorption of VOCs from indoor air is important for: (i) the accurate measurement of VOCs, and (ii) to apply mitigation strategies when high analyte concentrations are measured. In this study four VOCs (toluene, ethylbenzene, cumene and dichlorobenzene) were generated as a constant and controlled polluted air stream of VOCs from a dynamic atmospheric chamber. The effects of relative humidity, and sampling flow rate, on adsorption onto Tenax TA and the relatively new silica adsorbents SBA-15 or MCM-41 were studied. Air samples were collected and analyzed by thermal desorption followed by GC/MS. All sorbents were shown to be affected by changing the RH conditions from 25 to 80% RH, and sampling flow rates from 25 to 200 cm3 min−1, even when pollutant concentrations and sampled air volumes remained consistent. Although further work is required to examine the effect of the full RH range on scavenging potential, in this study Tenax TA was shown to provide best performance in high RH conditions whereas silica sorbents were more effective at low RH. Moreover it was shown that to provide accurate measurements in the field (e.g., when humidity conditions are fixed) it is suggested that Tenax TA is the preferred sorbent of choice as the masses of VOCs collected were less affected by changing the sampling flow rates.

Iron has been used previously in water decontamination, either unsupported or supported on clays, polymers, carbons or ceramics such as silica. However, the reported synthesis procedures are tedious, lengthy (involving various steps), and either utilise or produce toxic chemicals. Herein, the use of a simple, rapid, bio-inspired green synthesis method is reported to prepare, for the first time, a family of iron supported on green nanosilica materials (Fe@GN) to create new technological solutions for water remediation. In particular, Fe@GN were employed for the removal of arsenate ions as a model for potentially toxic elements in aqueous solution. Several characterization techniques were used to study the physical, structural and chemical properties of the new Fe@GN. When evaluated as an adsorption platform for the removal of arsenate ions, Fe@GN exhibited high adsorption capacity (69 mg of As per g of Fe@GN) with superior kinetics (reaching ∼35 mg As per g sorbent per hr) – threefold higher than the highest removal rates reported to date. Moreover, a method was developed to regenerate the Fe@GN allowing for a full recovery and reuse of the adsorbent in subsequent extractions; strongly highlighting the potential technological benefits of these new green materials.