Natural Inorganic Mineral Research Articles

A note on the use of crystal engineering to increase the opacity of terra verde inpainting pigment: Adulteration of green earths

Abstract Micallef et al. recently described in this Journal [38 (2019) 1–7] the use of crystal engineering methods to increase the opacity of terra verde (green earth) pigment for conservation inpainting purposes. In contrast to their chemical characterization of the pigment as comprising only natural inorganic minerals, this research shows that the commercial Verona green earth pigment used in their experiments contains a significant quantity of the synthetic organic pigment adulterant, copper phthalocyanine green (PG7 form). This bright green additive provides most of the color of their source pigment and is shown to be a common additive to so-called “green earth” colorants sold to artists and conservators. Their results must be reassessed in light of this oversight.

Halloysite nanotubes in analytical sciences and in drug delivery: A review

Halloysite (HNT) is a natural inorganic mineral that has many applications in manufacturing. This review (with 192 references) covers (a)the chemical properties of halloysites, (b)the effects of alkali and acid etching on the loading capacity and the release behavior of halloysites, (c)the use of halloysite nanotubes in analytical sciences and drug delivery, and (d)recent trends in the preparation of magnetic HNTs. Synthetic methods such as co-precipitation, thermal decomposition, and solvothermal method are discussed, with emphasis on optimal magnetization. In the analytical field, recent advancements are summarized in terms of applications of HNT-nanocomposites for extraction and detection of heavy metal ions, dyes, organic pollutants, and biomolecules. The review also covers methods for synthesizing molecularly imprinted polymer-modified HNTs and magnetic HNTs. With respect to drug delivery, the toxicity, techniques for drug loading and the various classes of drug-halloysite nanocomposites are discussed. This review gives a general insight on the utilization of HNT in analytical determination and drug delivery systems which may be useful for researchers to generate new ideas. Graphical abstract Schematic presentation of the structure of halloysite nanotubes, selected examples of modifications and functionalization, and represetative field of applications.

Oil absorbency of diatomite-embedded polypropylene meltblown composite structures

In this study, optimized conditions were established for diatomite grinding, which is a natural inorganic mineral with inherently high oil absorption capacity. Diatomite surface was modified with a fluorocarbon chemical and stearic acid via facile methods for enhancing compatibility between polypropylene and diatomite. Polypropylene/diatomite composites were generated in a twin screw extruder with/without using compatibilizer, and nonwoven structures were produced via meltblown technique. Pore size and void content analyses showed that addition of diatomite led to thicker fibers (1–17 µm (the neat polypropylene) vs. 1–32 µm (2 wt.% diatomite containing polypropylene)). Diatomite incorporation into polypropylene resulted in a rigid and brittle structure and a worsened oil absorption property (rust inhibitor oil absorption capacity: 1184% ± 105% (the neat polypropylene) vs. 718% ± 78% and 1089% ± 136% (2 wt.% diatomite containing polypropylene)). Increasing oil viscosity resulted in increased discrepancy among the oil absorption capacities of the neat polypropylene and diatomite containing polypropylene. Analysis of variance tests showed no changes or statistically insignificant differences in oil absorbency.

Risk mitigation by waste-based permeable reactive barriers for groundwater pollution control at e-waste recycling sites

Permeable reactive barriers (PRBs) have proved to be a promising passive treatment to control groundwater contamination and associated human health risks. This study explored the potential use of low-cost adsorbents as PRBs media and assessed their longevity and risk mitigation against leaching of acidic rainfall through an e-waste recycling site, of which Cu, Zn, and Pb were the major contaminants. Batch adsorption experiments suggested a higher adsorption capacity of inorganic industrial by-products [acid mine drainage sludge (AMDS) and coal fly ash (CFA)] and carbonaceous recycled products [food waste compost (FWC) and wood-derived biochar] compared to natural inorganic minerals (limestone and apatite). Continuous leaching tests of sand columns with 10wt% low-cost adsorbents were then conducted to mimic the field situation of acidic rainfall infiltration through e-waste-contaminated soils (collected from Qingyuan, China) by using synthetic precipitation leaching procedure (SPLP) solution. In general, Zn leached out first, followed by Cu, and finally delayed breakthrough of Pb. In the worst-case scenario (e.g., at initial concentrations equal to 50-fold of average SPLP result), the columns with limestone, apatite, AMDS, or biochar were effective for a relatively short period of about 20-40 pore volumes of leaching, after which Cu breakthrough caused non-cancer risk concern and later-stage Pb leaching considerably increased both non-cancer and lifetime cancer risk associated with portable use of contaminated water. In contrast, the columns with CFA or FWC successfully mitigated overall risks to an acceptable level for a prolonged period of 100-200 pore volumes. Therefore, with proper selection of low-cost adsorbents (or their mixture), waste-based PRBs is a technically feasible and economically viable solution to mitigate human health risk due to contaminated groundwater at e-waste recycling sites.

Nutrients Release from a Novel Gel-Based Slow/Controlled Release Fertilizer

A novel gel-based slow/controlled release fertilizer (G-CRF) was developed, which was produced by combining various natural, seminatural, and/or synthetic organic macromolecule materials and natural inorganic mineral with conventional NPK fertilizers. Its nutrient release characteristics were studied to compare with conventional fertilizers through the soil column leaching method. The influences of soil factors, including temperature, pH, water, and nutrient contents in the G-CRF on nutrient release, were also investigated through soil-water incubation method. These results indicated that the G-CRF had better effect on controlling release of N, P, and K nutrients, and the effect was more efficient when soil-water content was lower than 45% (w/w), temperature was below 35°C, and soil pH was in the range from weak acid to neutral. In addition, considering the effect of controlling nutrient release and cost of the materials in the G-CRF, it is recommended that the most feasible NPK nutrient contents in the G-CRF ranged from 30 to 35%.

Manipulating surface wettability and oil absorbency of diatomite depending on processing and ambient conditions

In this study, a diatomite sample, which is a natural inorganic mineral with inherently high water and oil absorption capacity, was subjected to grinding before surface modification. Afterwards, the diatomite surface was modified via facile methods using a fluorocarbon (FC) chemical and stearic acid (SA) in addition to the sol–gel fluorosilanization (FS) process. The water and oil wettability, and oil absorbency properties of the unmodified and modified diatomites were investigated in addition to diatomite characterizations such as chemical content, surface area, particle size distribution, morphology, and modification efficiency. It was revealed that the wettability was changed completely depending on the surface modification agent and the media used, while the oil absorbency property surprisingly did not change. On the other hand, the oil absorbency was worsened by the grinding process, whereas the wettability was not affected.

Histological reaction of the subcutaneous tissue of rats following implantation of bone morphogenetic protein (rhBMP-2) in inorganic bone scaffold and stimulation using low-power laser light

Objective: The aim of this study was to assess the histological reaction of the subcutaneous tissue of rats after the implantation of natural inorganic mineral scaffold from a calf femur containing recombinant human bone morphogenetic protein (rhBMP-2) and irradiated with low-power laser light. Material and methods: Sixteen Wistar rats were incised in the torso in a medial-longitudinal orientation, and the subcutaneous tissue of the left and right sides of the incision was pulled apart for implantation of the inorganic bone scaffold containing rhBMP-2. Diode laser light was applied to the right side implant at a dose of 8 J/cm2 for 3 minutes, forming two groups: G1 (control) and G2 (irradiated with laser). Implants and surrounding tissue were removed from four animals on days 7, 21, 40 and 112 for microscopic study. The histological results were assessed by means of grading (0 = absence, 1 = slight presence, 2 = representative and 3 = very representative), considering the following events: formation of osteoid structure, acute inflammation, chronic inflammation, fibrin deposition, neovascularization, foreign body granuloma and fibrosis. Results: The results showed no statistically significant differences in each of the four periods when the two groups were compared (p>0.05 – Mann-Whitney’s test). Conclusion: The natural inorganic scaffold from a calf femur with rhBMP-2 was a biocompatible combination. Under these conditions, the inductive capacity of rhBMP-2 for cell differentiation was inhibited. A slight hastening of tissue healing was shown in the group that was irradiated with low-power laser light.

Corrosion inhibition of steel in concrete with natural inorganic minerals in corrosive environments due to chloride attack

The purpose of this study is to assess the corrosion resistance of a reinforcing concrete bar from chloride attack when the concrete is blended with a natural inorganic mineral admixture.To this end, specimens with chloride ion contents resembling the chloride attack environment were prepared, and an autoclave accelerated corrosion test was conducted. The electrochemical values of the steel bars (i.e., half-cell potential and polarization resistance) were measured, and the measured polarization resistances were used to derive equations to determine the corrosion rate of the reinforcing bar. After curing for accelerated corrosion, the steel bars in concrete were analyzed with respect to corrosion shape, corrosion area rate, and corrosion weight loss rate.The results of the analysis showed that the concrete blended with a natural inorganic mineral admixture could control chloride-induced damage more thoroughly than the non-blended concrete under the same corrosive environments, regardless of the coating thickness. The improved corrosion resistance is attributed to the fact that the concrete blended with a natural inorganic mineral admixture could bind chloride ions and inhibit bleeding, thus prohibiting the formation of pores in the lower part of the reinforcing bar.

A study on improvement of durability of reinforced concrete structures mixed with Natural Inorganic Minerals

As a fundamental study on the corrosion resistance of reinforced concrete structures using Natural Inorganic Minerals exposed to carbonation environment. The test specimens were concrete(W/C = 60%) with Natural Inorganic Minerals content of 0% and 10%. Accelerated arbonation and autoclave corrosion accelerated curing were then conducted with them. The corrosion resistance of steel in concrete with Natural Inorganic Minerals content of 0% and 10% was examined by corrosion form, half-cell potential, polarization resistance, corrosion area and weight loss after 24 h of autoclave corrosion accelerated curing. The results of the study showed that as for steel in concrete with Natural Inorganic Minerals content of 10%, the corrosion resistance was more excellent than steel in concrete with Natural Inorganic Minerals content of 0%.