Arsenic removal from water/wastewater using adsorbents—A critical review

Green synthesis of metal nanoparticles using plants

A review on plants extract mediated synthesis of silver nanoparticles for antimicrobial applications: A green expertise.

The effects of solution pH and temperature on the adsorption of fluoride onto bone char made from cattle bones were investigated in this work. It was found that the maximum adsorption took place at pH 3 and the adsorption capacity decreased nearly 20 times augmenting the pH from 3 to 12. This behavior was attributed to the electrostatic interactions between the surface of bone char and the fluoride ions in solution. The adsorption capacity was not influenced by temperature in the range from 15 to 35 °C. A comparison of fluoride adsorption capacities among several adsorbents revealed that the adsorption capacity of the bone char was 2.8 and 36 times greater than those of a commercial activated alumina (F-1) and a commercial activated carbon (F-400). The adsorption capacity is considerably dependent upon the physicochemical properties of the bone char surface and the solution pH.

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Adsorption of Fluoride from Water Solution on Bone Char

Synthesis of metallic nanoparticles using plant extracts.

Purpose
The aim of this study was to prepare a highly active immobilized titania/silica photocatalyst and to test its performance in situ toward degradation of toluene as one of the major toxic indoor contaminants.

Photocatalytic degradation of gaseous toluene by using immobilized titania/silica on aluminum sheets.

Bioflocculation of high-ash Indian coals using Paenibacillus polymyxa

A simple colorimetric detection of melamine was studied using 15 nm (AuNPs-I), 30 nm (AuNPs-II), and 40 nm (AuNPs-III) citrate-capped gold nanoparticles (AuNPs). The AuNPs aggregated in aqueous solution in the presence of melamine, showing a visual color change from red to blue. This color change led to a shift in the absorption peak from 527 nm, 526 nm, and 525 nm to 638 nm, 626 nm, and 680 nm for AuNPs-I, AuNPs-II, and AuNPs-III, respectively. For all the three AuNPs, linearity was observed between the melamine concentration in aqueous solution and the absorbance ratios, A638/527, A626/525, and A680/526, respectively. The limit of detection (LOD) for melamine for the AuNPs-II was found to be 2.37 × 10−8 M (correlation coefficient R2 = 0.9745), which showed better sensitivity as compared to the LOD of the AuNPs-I and AuNPs-III, which were 3.3 × 10−8 M and 8.9 × 10−8 M, respectively. The synthesis of AuNPs-II also involved a lower HAuCl4 concentration compared with the other two types of AuNPs, which may reduce the process cost. The AuNPs-II was selected to analyze melamine in pre-treated milk samples, and the recovery percentage was in the range of 91–106%. Thus, the efficient detection of melamine was possible using AuNPs-II for the on-site detection without the aid of expensive instruments.

Colorimetric detection of melamine based on the size effect of AuNPs

In this paper, the effect of rhamnolipid biosurfactant on the electrokinetic and rheological behavior of nanozirconia particles is reported. The effect of pH, concentration of biosurfactant, and solids loading on ζ-potential and rheological behavior was investigated. ζ-potential measurements showed that adsorption of biosurfactant shifted the iso-electric point of zirconia with increasing biosurfactant concentration. The surface of zirconia became more electronegative in the presence of biosurfactant indicating a strong interaction. Maximum charge was obtained in the presence of about 230 ppm of biosurfactant. Rheological tests at pH 7 revealed that the zirconia suspension is viscous at high solids loading and addition of biosurfactant decreased the viscosity substantially especially at high solids loading (>50 wt%). Sedimentation tests confirmed that the biosurfactant is a good dispersant for zirconia particles at pH values of 7 and above.

Electrokinetic and Rheological Properties of Nano Zirconia in the Presence of Rhamnolipid Biosurfactant

High-performance epoxy composites find application in the aerospace industry. Although epoxy is a high-performance polymer, its fracture toughness is compromised due to its highly cross-linked nature. Nanomaterials such as carbon nanotubes (CNTs), graphene derivatives, and inorganic 2-dimensional (2D) nanomaterials are being explored to improve epoxy composites' mechanical properties. Graphene is one of the most popular 2D nano-reinforcing agents for epoxy composites. Following graphene discovery, the research community's attention was brought to various other few-atom thick 2D nanomaterials. Hence, apart from graphene, inorganic nanosheets such as transition metal dichalcogenides (TMDs), hexagonal boron nitride (hBN), etc., are also being studied as modifiers for enhancing the mechanical performance of epoxy composites. Graphene, TMDs and hBN are known to possess a high aspect ratio, high specific surface area and inherently high mechanical strength and stiffness, contributing to a stronger and tougher composite. Despite that, the challenges associated with these nanomaterials, such as dispersion issues, lack of standardization, underlying health hazards, etc., have hampered their commercialization. It has been long past a decade since the discovery of graphene, yet there are concerns regarding the lab to industry scale-up, and health and environmental hazards associated with nanomaterials for the fabrication of aerospace composites. This review offers a comprehensive literature survey and a perspective into the possible ways of bridging the gaps between the laboratory research and industrialization of 2D nanosheet-filled epoxy composites.

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Ashok M. Raichur

Papers

Photocatalytic degradation of gaseous toluene by using immobilized titania/silica on aluminum sheets.

Bioflocculation of high-ash Indian coals using Paenibacillus polymyxa

Colorimetric detection of melamine based on the size effect of AuNPs

Electrokinetic and Rheological Properties of Nano Zirconia in the Presence of Rhamnolipid Biosurfactant

Mechanical properties of aerospace epoxy composites reinforced with 2D nano-fillers: current status and road to industrialization