Bedabrata Saha

A mechanistic insight into enhanced and selective phosphate adsorption on a coated carboxylated surface

Trimesic acid (benzene-1,3,5-tricarboxylic acid, TMA) coated on basic alumina surface showed a significant and selective adsorption of phosphate from aqueous solution. Focus has been given on the selective adsorption and recovery of phosphate from a wide pH range solution which is the major drawback of phosphate removal in the known literature methods. TMA coated alumina exhibited high adsorption efficiency even with low phosphate concentration (approximately 1.0 mg/L) as well as low pH (approximately 1.0). Moreover, probable mechanism of high and consistent phosphate immobilizing capacity throughout a broad pH range (pH approximately 1.0-8.0) is discussed in detail. Adsorbed phosphate could be desorbed completely from adsorbent surface by treating with high alkaline solution. Discussion of adsorption process with two kinetic models revealed a fast kinetic rate and preference of second order model. A competitive study with other anions (chloride, nitrate and bromide) exhibited a high selective removal of phosphate over other anions. Influence of pH and temperature were also studied. Adsorption followed Langmuir isotherm model mostly and was thermodynamically favorable at even higher temperature (50 degrees C).

Efficient removal of chromate and arsenate from individual and mixed system by malachite nanoparticles

Malachite nanoparticles of 100-150 nm have been efficiently and for the first time used as an adsorbent for the removal of toxic arsenate and chromate. We report a high adsorption capacity for chromate and arsenate on malachite nanoparticle from both individual and mixed solution in pH ∼4-5. However, the adsorption efficiency decreases with the increase of solution pH. Batch studies revealed that initial pH, temperature, malachite nanoparticles dose and initial concentration of chromate and arsenate were important parameters for the adsorption process. Thermodynamic analysis showed that adsorption of chromate and arsenate on malachite nanoparticles is endothermic and spontaneous. The adsorption of these anions has also been investigated quantitatively with the help of adsorption kinetics, isotherm, and selectivity coefficient (K) analysis. The adsorption data for both chromate and arsenate were fitted well in Langmuir isotherm and preferentially followed the second order kinetics. The binding affinity of chromate is found to be slightly higher than arsenate in a competitive adsorption process which leads to the comparatively higher adsorption of chromate on malachite nanoparticles surface.

Trimesic acid coated alumina: an efficient multi-cyclic adsorbent for toxic Cu(II).

Biodegradable and eco-friendly organic acid, benzene-1,3,5-tri-carboxylic acid (trimesic acid), coated on commercial basic alumina, was used as adsorbent to remove toxic Cu(II) ion from aqueous solution. Adsorbent preparation was optimized and was characterized by SEM, EDX, FT-IR, and powder XRD pattern. Effect of various regulating parameters like reaction pH, adsorbent dose and initial Cu(II) concentration was studied in detail. Adsorption isotherms followed the Langmuir isotherm model and adsorption was thermodynamically favourable. Maximum adsorption capacity (Qm) for Cu(II) ion has been achieved as 10.80 mg/g. Detail kinetic study revealed that it followed second-order rate. Desorption of Cu(II) ion and re-usability of the adsorbent was also studied.

A comparative metal ion adsorption study by trimesic acid coated alumina: A potent adsorbent

Benzene-1,3,5-tri-carboxylic acid (trimesic acid, TMA) coated on basic alumina has been shown to be an effective adsorbent for Fe(III) and Fe(II) from aqueous solution. A comparative study on the adsorption of Fe(III) and Fe(II) revealed that TMA coated alumina is more selective towards Fe(III) than Fe(II). The maximum adsorptions of Fe(III) and Fe(II) were 26.6 mg/g and 8.4 mg/g, respectively. Fe(III)/Fe(II) adsorption was also compared in some cases with adsorption of Co(II) and Ni(II). Maximum uptakes (Qm) for Co(II) and Ni(II) were found much lower (approximately 1 mg/g) than Fe(III)/Fe(II). pH dependent studies have revealed that Fe(III) was adsorbed efficiently at high acidic condition (pH approximately 1.5) compared to Fe(II), Co(II) and Ni(II), while temperature did not have significant effect on the adsorption processes. Adsorption of Fe(III) and Fe(II) was quite rapid and thermodynamically favourable. Adsorption processes fitted well in Langmuir isotherm model and followed second order rate kinetics in all cases.

Surface-modification-directed controlled adsorption of serum albumin onto magnetite nanocuboids synthesized in a gel-diffusion technique

Magnetite nanocuboids have been synthesized via gel-diffusion technique in agarose gel. Here, the agarose gel matrix has been used as an organic template for formation and growth modification of magnetite. Gel mineralization mimics the membrane-based biomineralization, controls the diffusion process and gives the micro/nano environment for the crystal growth. We also attempt to understand the influence of different surface modifications of synthesized magnetite nanocuboids on protein interaction. For this purpose, magnetite particles were coated with trimesic acid (benzene-1,3,5-tricarboxylic acid) and stearic acid, which generates a hydrophilic and a hydrophobic modified surface, respectively. We report controlled adsorption behavior of bovine serum albumin (BSA) by surface modification of magnetite nanocuboids with different functional groups. The adsorption capacity of BSA increases on trimesic acid-coated surfaces compared to bare magnetite surfaces, while it decreases on stearic acid-coated surfaces. In situ fluorescence spectroscopy has been used to analyze the tertiary protein structure in the adsorbed state on these three surfaces. Partial unfolding in the tertiary structure of BSA was observed upon adsorption onto bare magnetite surfaces. On trimesic acid-coated surfaces, tertiary unfolding of BSA was greater than on bare magnetite surfaces, while BSA undergoes minor tertiary structural change on stearic acid-coated surfaces.

Tuning the selective interaction of lysozyme and serum albumin on a carboxylate modified surface

We have demonstrated an efficacious approach for tuning the selective adsorption of hen egg white lysozyme (HEWL) and bovine serum albumin (BSA) on the same carboxylate modified surface at different pH values. A basic alumina surface has been modified with trimesic acid to generate a carboxylated surface, and it has been used for the first time in differential protein interaction studies. We have found that very simple surface chemistry can be utilized for the controlled and selective adsorption of both proteins as a function of pH, which leads to the preferential binding of lysozyme over BSA at physiological pH ∼ 7.4. Significantly, we achieve a high retention of the enzymatic activity of the adsorbed lysozyme (∼98% of that of the native enzyme) at lower surface coverage, which also persists in different harsh conditions. In-depth conformational analysis revealed that selectively adsorbed lysozyme was partially unfolded but mostly retained its secondary structural content. In addition, we have also proposed an explanation of the possible interaction behaviour of the carboxylated surface with BSA and lysozyme molecules with the help of surface potential analysis, which provides an in-depth understanding of differential protein interaction.

Morphosynthesis of framboidal stable vaterite using a salicylic acid-aniline dye as an additive

Morphosynthesis and stabilization of pure framboidal vaterite microspheres using a salicylic acid–aniline dye as an additive has been reported in this paper. Formation and stabilization of vaterite crystals could be regulated by changing the dye concentration. Calcite rhombohedra were predominant species when no additive was added. As the concentration of dye was increased vaterite was more pronounced in the solution leading to the formation of pure framboidal vaterite (∼98% at 10 mM dye concentration). The size of these microspheres varied from 0.5 to 4.0 μm. Various instrumental analysis has been incorporated to study the dynamics of phase transformation throughout the process. Detailed analysis of TEM images reveals that vaterite microspheres were in turn aggregates of small vaterite nanospheres. The vaterite microspheres were stable up to a week in solution. The dissolution of the vaterite crystals to calcite was arrested by the presence of the dye at the nucleation process. The stability of the vaterite may be attributed to the strong electrostatic interaction of the Ca ions present on the surface of the crystal with the –COOH group of the dye. This finding opens up a new domain of organic additives to explore.

Morpho-physiological analysis of tolerance to aluminum toxicity in rice varieties of North East India

Aluminum (Al) is the third most abundant metal in earth crust, whose chemical form is mainly dependent on soil pH. The most toxic form of Al with respect to plants is Al3+, which exists in soil pH <5. Acidic soil significantly limits crop production mainly due to Al3+ toxicity worldwide, impacting approximately 50% of the world’s arable land (in North-Eastern India 80% soil are acidic). Al3+ toxicity in plants ensues root growth inhibition leading to less nutrient and water uptake impacting crop productivity as a whole. Rice is one of the chief grains which constitutes the staple food of two-third of the world population including India and is not untouched by Al3+ toxicity. Al contamination is a critical constraint to plant production in agricultural soils of North East India. 24 indigenous Indica rice varieties (including Badshahbhog as tolerant check and Mashuri as sensitive check) were screened for Al stress tolerance in hydroponic plant growth system. Results show marked difference in growth parameters (relative growth rate, Root tolerance index, fresh and dry weight of root) of rice seedlings due to Al (100 μM) toxicity. Al3+ uptake and lipid peroxidation level also increased concomitantly under Al treatment. Histochemical assay were also performed to elucidate uptake of aluminum, loss of membrane integrity and lipid peroxidation, which were found to be more in sensitive genotypes at higher Al concentration. This study revealed that aluminum toxicity is a serious harmful problem for rice crop productivity in acid soil. Based on various parameters studied it’s concluded that Disang is a comparatively tolerant variety whereas Joymati a sensitive variety. Western blot hybridization further strengthened the claim, as it demonstrated more accumulation of Glutathione reductase (GR) protein in Disang rice variety than Joymati under stressed condition. This study also observed that the emergence of lethal toxic symptoms occurs only after 48h irrespective of the dose used in the study.

Cowpea [Vigna unguiculata (L.) Walp].

Agrobacterium tumefaciens-mediated transformation is an efficient method for incorporating genes and recovering stable transgenic plants in cowpea because this method offers several advantages such as the defined integration of transgenes, potentially low copy number, and preferential integration into transcriptional active regions of the chromosome. Cotyledonary node explants of cowpea present an attractive target for T-DNA delivery followed by regeneration of shoots via axillary proliferation without involvement of a de novo regeneration pathway. In this chapter, we describe a detailed protocol for Agrobacterium-mediated transformation of the cowpea variety Pusa Komal. The seedling cotyledonary node explants are used for cocultivation with an Agrobacterium strain EHA105 harboring standard binary vector, pCAMBIA2301 or pNOV2819, and putative transformed plants are selected using aminoglycoside antibiotic or mannose as sole carbon source, respectively. The entire process includes explant infection to transgenic seed generation in greenhouse.