Performance of a novel iron infused biochar developed from Raphanus sativus and Artocarpus heterophyllus refuse for trivalent and pentavalent arsenic adsorption from an aqueous solution: mechanism, isotherm and kinetics study.

Fabrication of magnetic biochar was done by pyrolysis of waste leaves of Raphanus sativus (MRB) and Artocarpus heterophyllus (MJB) peel pretreated with FeCl3 was examined for As(III and V) adsorption from an aqueous solution. The synthesized bioadsorbents were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), particle size analysis (PSA), scanning electron microscope (SEM), energy dispersive x-ray (EDX), zeta potential, Vibrating sample magnetometer (VSM) and point of zero charge (pHZPC). MRB-800 exhibits greater efficiency toward the removal of both As species with qmax value 2.08 mg/g for As(III) and 2.03 mg/g for As(V). Whereas, the qmax value was 1.13 mg/g for As (III) and 1.26 mg g-1 for As (V) adsorption using MJB-800. Temkin and Freundlich isotherm were best fitted to the adsorption of As(III) and As(V) by MRB-800, respectively. Langmuir isotherm was best followed to the adsorption of As (III and V) by MJB-800. Pseudo-second-order kinetics was well simulated by the experimental data of As adsorption using both the bioadsorbents. Surface complexation and electrostatic attraction was dominant mechanism for As (III) and As (V) adsorption. Thermodynamic study shows that removal of As (III) was exothermic while the As (V) adsorption was endothermic for MRB-800 and MJB-800.

Based on the available literature, it was revealed that no work has been reported yet for the utilization of Raphanus sativus (Radish leaves) and Artocarpus heterophyllus (Jackfruit peel) waste for the preparation of magnetic biochar and its application for As(III) and As(V) removal for aqueous solution.

Adsorption of As(III) and As(V) from aqueous solution by magnetic biosorbents derived from chemical carbonization of pea peel waste biomass: Isotherm, kinetic, thermodynamic and breakthrough curve modeling studies.

The purpose of this research was to investigate the adsorption of arsenic (As) from aqueous solutions using MPAC-500 and MPAC-600 (magnetic-activated carbons synthesized from the peel of Pisum sativum (pea) pyrolyzed at 500 °C and 600 °C temperatures, respectively). The potential of both biosorbents for As adsorption was determined in batch and column mode. The characterization of both biosorbents was performed by energy dispersive spectroscopy, scanning electron microscope, pHZPC, particle size distribution, X-ray diffraction, zeta potential and Fourier-transform infrared spectroscopy. It was found that the efficiency of MPAC-600 was better than MPAC-500 for the adsorption of As(III) and As(V) ions. The adsorption capacities of MPAC-500 and MPAC-600 in removing As(III) were 0.7297 mg/g and 1.3335 mg/g, respectively, while the values of Qmax for As(V) on MPAC-500 and MPAC-600 were 0.4930 mg/g and 0.9451 mg/g, respectively. The Langmuir isotherm model was found to be the best fit for adsorption of As(III) by MPAC-500 and MPAC-600, as well as adsorption of As(V) by MPAC-500. The Freundlich isotherm model, on the other hand, was optimal for As(V) removal with MPAC-600. With R2 values close to unity, the pseudo-second-order kinetics were best fitted to the adsorption process of both As species. The Thomas model was used to estimate the breakthrough curves. The effects of coexisting oxyanions and regeneration studies were also carried out to examine the influence of oxyanions on As adsorption and reusability of biosorbents.

Synthesis of novel biochar from waste plant litter biomass for the removal of Arsenic (III and V) from aqueous solution: A mechanism characterization, kinetics and thermodynamics.

The present study is focusing on utilization of a new feedstock material for the preparation of biochar. The dry waste leaves litter of Tectona and Lagerstroemia speciosa was used for synthesizing the biochar at 800 °C for 1 h in muffle furnace represents as TB 800 and LB 800 and then used for the removal of As(III) and As(V) from aqueous solution. The prepared biochar materials had a crystalline structure and was characterized by using Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), Brunaur emmit teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Zeta potential, particle size and X-ray photoelectron spectroscopy (XPS). In regeneration study it was observed that prepared biochar material could be used up to four times with good removal percentage of Arsenic (III and V). The experimental data fitted well by Langmuir model for As(V) removal using TB 800 and LB 800, Freundlich model for As(III) removal by LB 800 and Temkin model for As(III) removal by TB 800. Pseudo-second-order kinetics was followed and best fitted with the obtained data of As(III) and (V) removal. Thermodynamics study revealed that the process of adsorption was endothermic for the removal of As(III) and exothermic for the adsorption of As(V) using TB 800 and LB 800. The adsorption capacity obtained for the removal of As(III) was 666.7 µg/g and 454.54 µg/g for TB 800 and LB 800, respectively and adsorption capacity for As(V) was 1250 µg/g for TB 800 and 714.28 µg/g was attained by LB 800.

As(III) and As(V) removal by using iron impregnated biosorbents derived from waste biomass of Citrus limmeta (peel and pulp) from the aqueous solution and ground water.

Now a day's biosorbents with magnetic properties have been applied for water and wastewater treatment process, because of its magnetic nature it can be easily separated and can be reused more than one time. In the present study, two magnetic biosorbents were synthesized from waste biomass of Citrus limetta (peel and pulp) at 500 °C temperature represented as PAC-500 and PPAC-500. These biosorbents were effectively used for the removal of As(III) and As(V) from an aqueous solution and groundwater samples. The prepared biosorbents were characterized by using Brunauer Emmett Teller (BET), Zeta potential, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Disperssive X-ray (EDS), X-ray Diffraction (XRD) and Particle Size Analyzer (PSA). Isotherms, kinetics and thermodynamics were also applied to the obtained experimental data. The regeneration study revealed that the biosorbent can be recycled up to four cycles. The adsorbent capacity of PAC-500 and PPAC-500 for the sorption of As(III) was 714.28 µg/g and 526.31 µg/g, respectively, whereas the qmax value for As(V) sorption was 2000 µg/g for both the biosorbents (PAC-500 and PPAC-500). The effect of competitive ions was also studied that shows that the presence of H2PO4- and CO32 have negative effects on the sorption of As(III) and As(V). Arsenic is very toxic and it is a more important subject for consideration, therefore it is necessary to develop a low cost material that is very efficient in removing As from ground water contaminated with As water.

Adsorptive Removal of Fluoride from Aqueous Solution by Biogenic Iron Permeated Activated Carbon Derived from Sweet Lime Waste.

In this study, biogenic activated carbon were successfully synthesized from Citrus limetta pulp residue, and applied to remove fluoride from an aqueous solution. For the synthesis activated carbon of biosorbents, raw materials were heated in muffle furnace at two different temperatures i.e. (250 °C and 500 °C) and were noted as ACP-250 and ACP-500. The prepared biosorbents were characterized through scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). Batch adsorption studies were performed with varying temperature, dosage, pH, and various initial concentrations. Adsorption isotherms and the reaction kinetics were also analyzed in order to understand the adsorption mechanism. The results of this study shows that the maximum removal achieved was approximately (86 and 82) % of ACP-500 and ACP-250, respectively. The isotherm results show that the Langmuir isotherm model fitted better, with monolayer adsorption capacity of 12.6 mg/g of fluoride. However, for kinetic study, the pseudo-second-order kinetics fitted well. The synthesized materials at different temperature were highly effective for the removal of fluoride from water, with reusability of three to four times.

Biochemical and structural characterization of a novel halotolerant cellulase from soil metagenome.

Cellulase catalyzes the hydrolysis of ß-1,4-linkages of cellulose to produce industrially relevant monomeric subunits. Cellulases find their applications in pulp and paper, laundry, food and feed, textile, brewing industry and in biofuel production. These industries always have great demand for cellulases that can work efficiently even in harsh conditions such as high salt, heat, and acidic environments. While, cellulases with high thermal and acidic stability are already in use, existence of a high halotolerant cellulase is still elusive. Here, we report a novel cellulase Cel5R, obtained from soil metagenome that shows high halotolerance and thermal stability. The biochemical and functional characterization of Cel5R revealed its endoglucanase activity and high halostability. In addition, the crystal structure of Cel5R determined at 2.2 Å resolution reveals a large number of acidic residues on the surface of the protein that contribute to the halophilic nature of this enzyme. Moreover, we demonstrate that the four free and non-conserved cysteine residues (C65, C90, C231 and C273) contributes to the thermal stability of Cel5R by alanine scanning experiments. Thus, the newly identified endoglucanase Cel5R is a promising candidate for various industrial applications.

Purification and characterization of a novel enantioselective hydrolase from Bacillus subtilis.

Screening of the micro-organisms from an in-house microbial culture repository, identified a bacterial strain bearing membrane-bound, inducible ester hydrolase activity. The strain designated as RRL-BB1 has been identified as Bacillus subtilis by 16 S rRNA typing. Its application in the kinetic resolution of several racemates, including drug intermediates, showed moderate to high enantioselectivity. The enzyme, designated as BBL, exhibited high enantioselectivity (ee approximately 99%) with acyl derivatives of unsubstituted and substituted 1-(phenyl)ethanols and 1-(6-methoxy-2-naphthyl)ethanols. With acyl derivatives of 2-(6-methoxy-2-naphthyl)propan-1-ol, moderate enantioselectivity was observed. The enzyme also showed moderate enantioselectivity with alkyl esters of carboxylic acids i.e. 2-bromopropanoic acid and 2-hydroxy-4-phenylbutanoic acid. The enzyme was purified to >90% purity from cell-free extract of RRL-BB1 with 26% overall yield. The purified enzyme exhibited hydrolase activity without any noticeable decrease in the rate of hydrolysis or the enantioselectivity profile. A specific activity of 450 units/mg protein resulted after at least a 200-fold purification of the crude cell-free extract. The key purification step was the irreversible adsorption of the salt-precipitated crude enzyme on hydrophobic resin, in the presence of a low salt concentration, and desorption of the enzyme with a linear gradient of 1% sodium cholate. The purified enzyme was a 45 kD monomer as shown by SDS/PAGE. The N-terminal amino acid sequence of the purified enzyme was determined as Thr-Lys-Leu-Thr-Val-Gln-Thr-Arg-Asp-Gly-Ala-Leu-Arg-Gly-Thr. The N-terminal sequence did not bear any homology with other known bacterial lipases. BBL is maximally active at 37 degrees C, pH 8.0 and fairly stable up to 40 degrees C, pH 6-10. The enzyme is insensitive to EDTA but inhibited by serine protease inhibitor PMSF. Its activity (72%) was retained in the presence of the anionic detergent SDS at a concentration of 0.2% (w/v).