Preparation of Graphene Oxide/Cellulose Composites with Microcrystalline Cellulose Acid Hydrolysis Using the Waste Acids Generated by the Hummers Method of Graphene Oxide Synthesis

The Hummers method is the most commonly used method to prepare graphene oxide (GO). However, many waste acids remain in the raw reaction mixture after the completion of this reaction. The aim of this study was to reuse these waste acids efficiently. In this study, microcrystalline cellulose (MCC) was directly dissolved in the mixture after the high-temperature reaction of the Hummers method. The residual acid was used to hydrolyze MCC, and the graphene oxide/microcrystalline cellulose (GO/MCC) composites were prepared, while the acid was reused. The effects of MCC addition (0.5 g, 1.0 g, and 1.5 g in 20 mL) on the properties of the composites were discussed. The structure, composition, thermal stability, and hydrophobicity of GO/MCC composites were characterized and tested by SEM, XRD, FTIR, TG, and contact angle tests. The results showed that MCC could be acid hydrolyzed into micron and nano-scale cellulose by using the strong acidity of waste liquid after GO preparation, and it interacted with the prepared GO to form GO/MCC composites. When the addition amount of MCC was 1 g, the thermal stability of the composite was the highest due to the interaction between acid-hydrolyzed MCC and GO sheets. At the same time, the hydrophobic property of the GO/MCC composite is better than that of the GO film. The freeze-dried GO/MCC composites are more easily dispersed in water and have stronger stability.

Spatial prediction of soil acidity and nutrients for site-specific soil management in Bedele district, Southwestern Ethiopia

Background Understanding the spatial variability of soil properties is useful to tailor site-specific agricultural inputs to enhance crop production on a sustainable basis. This study was aimed to assess and map the spatial patterns of soil acidity and nutrients using geostatistical methods and support site-specific lime and fertilizer recommendations in Bedele district, Southwestern Ethiopia. Methods Soil samples were collected from agricultural land at a depth of 20 cm using grid sampling technique. The semivariogram analysis was performed for accurate spatial prediction and the kriging technique was used for interpolation of soil parameters. Results Soil pH varied between 4.5 and 6.8. Soil organic carbon (OC) content ranged from 0.3 to 5.6% and the mean soil OC density was 0.81 kg m−2. Available phosphorus (AvP) ranged from 0.8 to 38.6 mg kg−1 and nearly 80.23% of the soils exhibited very low to low AvP that could be due to fixation by strong acidity. Soils of the study area exhibited very high exchangeable potassium (K), but very low exchangeable calcium (Ca) and magnesium (Mg). The potassium to magnesium ratio (K:Mg) ranged from 0.2:1 to 10.9:1, while the values of calcium to magnesium ratio (Ca:Mg) varied between 0.3 and 3.4. Among the soil parameters, exchangeable Ca (CV = 54%) and K:Mg ratio (CV = 57.62%) were more variable than other soil parameters. Spatial variability was lowest for soil pH (CV = 10%). Conclusions Major portions of the study site were affected by strong acidity (pH ≤ 5.5). Accordingly, about 89% of the soils require lime that varied between 0.09 and 3.6 tons ha−1. In addition to soil acidity, deficiency of available P, Ca, and Mg were the major liming factors affecting crop production in the study area. Digital soil mapping was used to show the spatial variability of soil acidity and nutrients across agricultural land and applied for efficient lime and nutrients advisory works.

Bacterial communities in the polluted area of pyrite tailings: From the upstream, pollutant source, and to the downstream

Pyrite tailings can cause serious pollution to the surface water as the strong acidity, high iron and sulfate concentration in the leachate. The bacterial communities of pyrite tailings polluted area were still unclear which could restrict the recognition of the pyrite tailings pollution effect and further impede the development of microbial or ecology treatment technologies. In this study, the bacterial communities in the polluted area of pyrite tailings, from the upstream, pollutant source, and to the downstream, were analyzed with Illumina HiSeq sequencing. Results showed that Acinetobacter and Flavobacterium were abundant in the water and sediment of upstream and downstream while Bacteroides, Lactobacillus, and Akkermansia were abundant in the pollutant source. Sulfur-metabolizing or iron-metabolizing bacteria extensively existed in the polluted area in which Acidiferrobacter, Ferrithrix, and Desulfovibrio played crucial roles on the whole communities. Sulfur-metabolizing bacteria (e.g. Thiomonas, Sulfurospirillum, and Desulfobulbus) and iron-metabolizing bacteria (e.g. Ferrimicrobium, Ferrithrix, and Ferrovum) were introduced to the river polluted by pyrite tailings. Pyrite tailings can remarkably change the physicochemical characteristics and bacterial communities of river water and sediment.

Relationship between Acidity and Activity on Propane Conversion over Metal-Modified HZSM-5 Catalysts

A systematic study of the comparative performances of different metal-impregnated HZSM-5 catalysts (Zn, Ga, Mo, Co, and Zr) for propane conversion is presented. The physicochemical properties of catalysts were characterized by means of XRD, BET, SEM, TEM, FTIR, XPS, 27Al MAS NMR, NH3-TPD and Py-FTIR. It was found that the acidities of the catalysts were significantly influenced by loading metal. More specifically, Mo-, Co- or Zr-modified catalysts showed a large metal size and low acidic density, resulting high olefin selectivity, while Zn- or Ga-modified catalysts maintained their small metal size and acidic density, and mainly reduced B/L due to the Lewis acid sites created by Zn or Ga species, resulting in high aromatics selectivity. Experimental results also showed that there is a balance between metals size and medium and strong acidity on propane conversion. Moreover, based on the different acidity of metal-modified HZSM-5 catalysts, the mechanism of propane conversion was also discussed.

Kraft Lignin Ethanolysis over Zeolites with Different Acidity and Pore Structures for Aromatics Production

To utilize its rich aromatics, lignin, a high-volume waste and environmental hazard, was depolymerized in supercritical ethanol over various zeolites types with different acidity and pore structures. Targeting at high yield/selectivity of aromatics such as phenols, microporous Beta, Y, and ZSM-5 zeolites were first examined in lignin ethanolysis, followed by zeolites with similar micropore size but different acidity. Further comparisons were made between zeolites with fin-like and worm-like mesoporous structures and their microporous counterparts. Despite depolymerization complexity and diversified ethanolysis products, strong acidity was found effective to cleave both C–O–C and C–C linkages of lignin while mild acidity works mainly in ether bond breakdown. However, when diffusion of gigantic molecules is severe, pore size, particularly mesopores, becomes more decisive on phenol selectivity. These findings provide important guidelines on future selection and design of zeolites with appropriate acidity and pore structure to promote lignin ethanolysis or other hydrocarbon cracking processes.

Construction of a Keggin heteropolyacid/Ni-MOF catalyst for esterification of fatty acids

The developed heteropolyacids immobilized on Ni-MOF catalysts have strong acidity and perform well in esterification.

Physiological Responses of Earthworm Under Acid Rain Stress

Acid rain has become one of the major global environmental problems, and some researches reported that acid rain may have a certain inhibition on soil biodiversity. Besides this, it is well known that earthworm (Eisenia fetida) plays an important role in the functioning of soil ecosystems. For this point, we conducted a series of experiments to investigate whether acid rain would take effects on earthworms. In the present study, the earthworms were incubated on filter paper and in soil under acid rain stress. The mortality and behavior of earthworms were recorded, and epidermal damage and the activity of the CYP3A4 enzyme were measured for the tested earthworms. Our experimental results showed that the earthworms could not survive in the acid rain stress of pH below 2.5, and acid rain with weak acidity (i.e., 4.0 ≤ pH ≤ 5.5) promoted the activity of the CYP3A4 enzyme in the earthworms, while acid rain with strong acidity (i.e., 3.0 ≤ pH ≤ 3.5) inhibited it. Moreover, the degree of damage in sensitive parts of the earthworms increased with the decrease of pH value. This study suggests that acid rain can cause discomfort response and the direct epidermal damage of earthworms, and even kill them.

The Effect of Dental Enamel Pre-Etching for Self-Etching Adhesives According to their Primer pH: An In Vitro Bond Strength, Etching Pattern and Adhesive Failure Evaluation

Dental enamel pre-etching before the application of a self-etching adhesive (SEA) has different effects depending on the pH of the adhesive acidic monomer, being not always beneficial. This study aimed to evaluate the shear bond strength (SBS), etching pattern, and fracture type of different acidity SEAs, with and without previous phosphoric acid etching. One-hundred-sixty bovine incisors were subjected to SBS testing with the following adhesive systems: Adper-Prompt-L-Pop (APLP) (strong acidity), Futurabond NR (FB), AdheSE One F (AD) (intermediary acidity) and Clearfil SE (CSE) (mild acidity), with and without previous phosphoric acid etching. Results were evaluated applying both ANOVA and Tukey’s test. Besides, forty bovine incisors were used to assess etching patterns using scanning-electron-microscopy (SEM). Adhesive failure was evaluated, classifying bond failure as one of five types. SBS averages were (MPa): without pre-etching: APLP (20.61±11.84), CSE (17.29±10.16), FB (11.44±6.99), AD (7.88±4.85) and with pre-etching: APLP (16.17±9.68), CSE (25.96±11.75), FB (20.12±9.39), AD (14,28±9.42). Different enamel etching patterns were observed depending on each SEA’s pH and whether the surface was pre-etched. Most fracture failures were adhesive type. Less than 10 % were cohesive type. SBS improves when mild and intermediary strength SEAs are pre-etched. However, it decreases when strong SEAs are pre-etched.