An overview on the key advantages and limitations of batch and dynamic modes of biosorption of metal ions.

Water purification using adsorption is a crucial process for maintaining human life and preserving the environment. Batch and dynamic adsorption modes are two types of water purification processes that are commonly used in various countries due to their simplicity and feasibility on an industrial scale. However, it is important to understand the advantages and limitations of these two adsorption modes in industrial applications. Also, the possibility of using batch mode in industrial scale was scrutinized, along with the necessity of using dynamic mode in such applications. In addition, the reasons for the necessity of performing batch adsorption studies before starting the treatment on an industrial scale were mentioned and discussed. In fact, this review article attempts to throw light on these subjects by comparing the biosorption efficiency of some metals on utilized biosorbents, using both batch and fixed-bed (column) adsorption modes. The comparison is based on the effectiveness of the two processes and the mechanisms involved in the treatment. Parameters such as biosorption capacity, percentage removal, and isotherm models for both batch and column (fixed bed) studies are compared. The article also explains thermodynamic and kinetic models for batch adsorption and discusses breakthrough evaluations in adsorptive column systems. The review highlights the benefits of using convenient batch-wise biosorption in lab-scale studies and the key advantages of column biosorption in industrial applications.

Analytical electron microscopy of black carbon and microaggregated mineral matter in Amazonian dark Earth.

Black carbon (BC) is one of the most stable forms of soil organic matter. Its surface functional groups and structure have been well characterized by a range of analytical methods. However, little is known about the mechanisms of interactions between the BC particles and the surrounding mineral matter. In this paper a range of microscopy techniques, such as transmission electron microscopy and scanning transmission electron microscopy, were used to investigate the possible reactions of BC particles within microaggregates (<2 mm) found in Amazonian dark Earth. Attention is given to the interactions that occur at the interfacial regions between the organic and inorganic phases. Examination of Amazonian dark Earth showed that the carbon-rich phase detected within the BC particles has a significant calcium concentration and a high density of micropores was found at the BC-mineral interface. These observations provide evidence to support suggested mechanisms of interaction between these phases.

Fabrication and characterization of graphene hydrogel via hydrothermal approach as a scaffold for preliminary study of cell growth.

BACKGROUND: Three-dimensional assembly of graphene hydrogel is rapidly attracting the interest of researchers because of its wide range of applications in energy storage, electronics, electrochemistry, and waste water treatment. Information on the use of graphene hydrogel for biological purposes is lacking, so we conducted a preliminary study to determine the suitability of graphene hydrogel as a substrate for cell growth, which could potentially be used as building blocks for biomolecules and tissue engineering applications. METHODS: A three-dimensional structure of graphene hydrogel was prepared via a simple hydrothermal method using two-dimensional large-area graphene oxide nanosheets as a precursor. RESULTS: The concentration and lateral size of the graphene oxide nanosheets influenced the structure of the hydrogel. With larger-area graphene oxide nanosheets, the graphene hydrogel could be formed at a lower concentration. X-ray diffraction patterns revealed that the oxide functional groups on the graphene oxide nanosheets were reduced after hydrothermal treatment. The three-dimensional graphene hydrogel matrix was used as a scaffold for proliferation of a MG63 cell line. CONCLUSION: Guided filopodia protrusions of MG63 on the hydrogel were observed on the third day of cell culture, demonstrating compatibility of the graphene hydrogel structure for bioapplications.

Simple room-temperature preparation of high-yield large-area graphene oxide.

Graphene has attracted much attention from researchers due to its interesting mechanical, electrochemical, and electronic properties. It has many potential applications such as polymer filler, sensor, energy conversion, and energy storage devices. Graphene-based nanocomposites are under an intense spotlight amongst researchers. A large amount of graphene is required for preparation of such samples. Lately, graphene-based materials have been the target for fundamental life science investigations. Despite graphene being a much sought-after raw material, the drawbacks in the preparation of graphene are that it is a challenge amongst researchers to produce this material in a scalable quantity and that there is a concern about its safety. Thus, a simple and efficient method for the preparation of graphene oxide (GO) is greatly desired to address these problems. In this work, one-pot chemical oxidation of graphite was carried out at room temperature for the preparation of large-area GO with ~100% conversion. This high-conversion preparation of large-area GO was achieved using a simplified Hummer's method from large graphite flakes (an average flake size of 500 µm). It was found that a high degree of oxidation of graphite could be realized by stirring graphite in a mixture of acids and potassium permanganate, resulting in GO with large lateral dimension and area, which could reach up to 120 µm and ~8000 µm(2), respectively. The simplified Hummer's method provides a facile approach for the preparation of large-area GO.

Thermodynamic aspects of sorption of Fe2+ onto unbleached Kraft fibres.

The sorption of Fe(2+) onto unbleached kraft fibre was investigated at different conditions such as pH, temperature, and concentrations. The sorption, which increased with concentration and temperature, followed the Langmuir isotherm. Thermodynamically, the process was spontaneous and endothermic. It was found that the precipitation of Fe(2+) was highly dependent on pH and reached 100% when pH exceeded approximately 8.

Chest pain in the early postoperative period after laparoscopic adjustable gastric banding: four case reports.

Laparoscopic adjustable gastric banding (LAGB) is gaining popularity as a technique for achieving effective weight loss in the severely obese population. It is a minimally invasive procedure and the reported early morbidity is low. However, we have observed at our institution that occasional patients complain of central chest pain, mimicking angina (verbal pain score of > 7 out of 10), within 2 h after the procedure. This is a worrying symptom because obesity is known to be a major risk factor for developing cardiovascular complications. We have now performed 250 LAGB operations at our hospital. The following four case reports document our patients who presented with early chest pain postoperatively. Common characteristics of male gender, morbid obesity and some degree of obstructive sleep apnoea were identified among the cases. The aetiology of the chest pain is uncertain; nevertheless, close monitoring is vital to exclude pathological events such as acute coronary syndrome.