Novel adsorbents for the removal of toxic cadmium ions from polluted water.

Cadmium is one of the most toxic heavy metal ions found in wastewaters and its remedial methods are globally investigated. Removal methods based on biomaterials as adsorbents are proving to be simple, effective and eco-friendly. In the present investigation, bio-adsorbents derived from Cochlospermum regium plant stems (CRSP) and its active carbon (CRAC) are observed to have good adsorption for toxic cadmium ions. Hence, extraction conditions are optimized for maximum Cd-extraction: 55.0% with 'CRSP' and 70.0% with 'CRAC', from Cd2+ solutions of concentration: 25.0 mg/L. The adsorption capacities are 6.9 mg/g with CRSP and 12.6 mg/g with 'CRAC'. When 'CRAC' is impregnated with nano-CeO2 (CRAC.nCeO2) and is used as adsorbent, the percentage of Cd-extraction is increased to 90.0% and adsorption capacity to 22.5 mg/g at the optimized extraction conditions. To overcome the agglomeration of nanoparticles, the 'CRAC.nCeO2' is immobilized in Zr-alginate beads and thus obtained beads are investigated as adsorbent. With beads (CRAC.nCeO2-Zr.alg), the percentage of Cd-adsorption is enhanced to 95.0% and adsorption capacity to 24.6 mg/g. The adsorbents are characterized by adopting XRD and FTIR techniques. The adsorption mechanism is assessed by evaluating thermodynamic parameters, isotherm and kinetic models. The thermodynamic parameters and FTIR spectral characteristics indicate the formation of 'surface complex' between Cd2+ and adsorbent's functional groups. The adsorption follows Freundlich isotherm and pseudo-second order model. Many co-ions have not effected the percentage of extraction and interestingly, the presence of some cations (Al3+ and Fe3+) have synergistically enhanced the Cd-extraction. Spent sorbents can be regenerated and reused with marginal loss of adsorption capacity. The adsorbents developed are successfully used to treat real Cd-polluted wastewater. The novelty of the present investigation is that the effective, eco-friendly, renewable and robust sorbents with high sorption capacities are developed for Cd-remediation of water.

The merit of the present investigation is that adsorbents with high sorption capacities, are developed based on bio materials of Cochlospermum regium and nano-CeO₂. Zirconium alginate beads doped with nano-CeO₂ and active carbon of Cochlospermum regium stems, are found to be highly effective for Cd-removal and spent adsorbent can be regenerated and re-used for five cycles.

Stem powder and its active carbon of Arachis hypogaea plant for lead (II) removal: application to treat battery-based industrial effluents.

Stem powder and its active carbon of Arachis hypogaea plant are identified to have strong adsorptivity for lead ions. The bio-sorbents are characterized by conventional methods including XRD and FTIR analysis. These biomaterials are investigated for their maximum adsorption for lead ions by optimizing the extraction conditions. The maximum removal is observed in the pH range of 6-7 for both sorbents. With stem powders, the removal is 76.0% from a simulated lead solution of concentration: 20.0 mg/L with 1.5 g/L of the sorbent and at an equilibration time of 2.0 h. With the active carbon, the maximum extraction of: 86.0% is observed at pH: 6.5 with 1.0 g/L of the sorbent after an equilibration time of 1.5 h. The sorption capacities are 32.0 mg/g for stem powders, and 40.5 mg/g for active carbon. Many co-ions have marginal interference. Spent adsorbents can be recycled after regeneration. Thermodynamic investigations reveal the spontaneity and endothermic nature of adsorption. High ΔH values viz., 26.45 kJ/mole for AHSP and 46.40 kJ/mole for AHSAC, confirm the bonding of Pb2+ ions with the sorbents is either "ion-exchange" and/or a sort of "complex formation." The disorder at the solid and liquid boundary is indicated by high positive ΔS values and it is a favorable condition for good Pb2+ adsorption. On analysis of different kinetic and isotherm models, the sorption of Pb2+ ions follows Pseudo-2nd order and Langmuir models. This confirms the mono-layer adsorption of Pb2+ ions on the humongous surface of the sorbent. The adsorbents are successfully applied to treat industrial effluent samples.

In the present investigation, stem powder and its active carbon of Arachis hypogaea plant are identified to have strong adsorptivity for highly toxic lead ions. Successful methodologies are developed for the maximum extraction of lead ions from industrial wastewater at a convenient nearly neutral pH. The adsorption capacities are as high as: 32.0 mg/g for stem powders and 40.5 mg/g for active carbon. The sorbents are characterized and the sorption mechanism is investigated. The novelty of the present investigation is that highly toxic lead ions can be easily removed from polluted water by using simple bio-adsorbents by adopting convenient procedures.

Synthesis and characterization of two known and one new impurities of dolutegravir: In silico evaluation of certain intermediates against SARS CoV-2 O-ribose methyltransferase (OMTase).

Besides its use against HIV infection the marketed anti-retroviral drug dolutegravir attracted attention as a potential agent against COVID-19 in multiple AI (artificial intelligence) based studies. Due to our interest in accessing the impurities of this drug we report the synthesis and characterization of three impurities of dolutegravir one of which is new. The synthesis of O-methyl ent-dolutegravir was accomplished in three-steps the first one involved the construction of fused 1,3-oxazinane ring. The cleavage of -OEt ether moiety followed by methylation afforded the target compound. The second impurity i.e. N-(2,4-difluorobenzyl)-4-methoxy-3-oxobutanamide was synthesized via a multi-step method involving sequentially the keto group protection, ester hydrolysis, acid chloride formation followed by the reaction with amine and finally keto group deprotection. The synthesis of new or dimer impurity was carried out via another multi-step method similar to the previous one starting from ethyl 4-chloro acetoacetate. The methodology involved preparation of ether derivative, keto group protection, ester hydrolysis, preparation of amide derivative via acid chloride formation in situ and then keto group deprotection for a longer duration. The last step afforded the target compound for which a plausible reaction mechanism has been proposed. All three impurities were prepared in gram scale (minimum 2 g and maximum 8 g). The in silico evaluation of three selected synthesized intermediates e.g. 7, 8 and 9 (structurally similar to dolutegravir) against SARS CoV-2 O-ribose methyltransferase (OMTase) (PDB: 3R24) indicated that compound 7 could be of interest as a possible inhibitor of this protein.

Simultaneous removal of lead and cadmium ions from simulant and industrial waste water: using Calophyllum Inophyllum plant materials as sorbents.

NOVELTY STATEMENT: The merit of this investigation is that simple and effective bio-sorbents based on Calophyllum inophyllum plant materials with high sorption capacities, are developed for the simultaneous removal of the toxic Pb2+ and Cd2+ at neutral or nearly neutral pHs. These sorbents are successful in water remediation of Pb2+ and Cd2+ ions from real effluents from industries. These findings have great significance as the identified bio-sorbents are simple, effective and renewable in extracting highly toxic lead and cadmium ions from the effluents from industries or polluted water.

High resolution and high throughput analytical methods for d-tagatose and process related impurities using capillary electrophoresis.

d-tagatose is a low calorie multifunctional rare ketohexose sugar with sweetness similar to that of sucrose and it has high potential benefits for food and pharmaceutical industries. It is found in traces in some fruits as a natural component. In view of its high demand as a substitute for sugar, mass production of d-tagatose through enzymatic conversion of Lactose to d-tagatose is adopted. The existing HPLC method has limitations with respect sensitivity and resolution in quantification and monitoring of d-tagatose in the presence of its process related impurities. In the present investigation a new robust, fast and green analytical technique has been developed based on capillary electrophoresis (CE) for the separation and quantification of d-tagatose in presence of other sugars: Lactose, d-glucose, d-galactose and d-talose. Optimum conditions are found to be: Back Ground Electrolyte (BGE): 36 mM of Na2HPO4 and 130 mM of NaOH; pH: 12.6; voltage: +18 kV for high resolution and -18 kV for high throughput methods with direct UV-Detector at 265 nm. At these optimum conditions, good separation between the sugars is achieved in less than 20 min for high resolution and less than 4 min for high throughput methods. The developed methodology is validated as per ICHQ2R1 guide lines and successfully applied for monitoring d-tagatose during the enzymatic conversion of Lactose/d-galactose to d-tagatose and also to determine the unknown amounts of d-tagatose in crystallized samples and further, it is used in identifying the d-tagatose in fruits.

Synthesis of nanoZrO2 via simple new green routes and its effective application as adsorbent in phosphate remediation of water with or without immobilization in Al-alginate beads.

Nano particles of ZrO2 of average size 10.91 nm are successfully synthesized via green routes from a solvent blend of water and ethylene glycol (4:1 v/v). Bio-extract of seeds of Sapindus plant is employed as stabilizing and/or capping agent and homogeneous method of precipitation is adopted to generate the precipitating agent. The nZrO2 particles are immobilized in aluminum alginate beads (nZrO2-Al- alig). Nano-ZrO2 and beads are investigated as adsorbents for the extraction of phosphate from water. The controlling physicochemical parameters are studied for the maximum phosphate removal using simulate water. The optimum conditions are: pH: 7; sorbent dosage: 0.1 g/100 mL for nZrO2 and 0.08 g/100 mL for beads; equilibration time: 30 min.for nZrO2 and 35 min for beads; initial phosphate concentration: 50 mg/L; temperature: 30 ± 1 °C; 300 rpm. The adsorption capacities are: 126.2 mg/g for nZrO2 and 173.0 mg/g for 'nZrO2-Al- alig' and they are higher than many reported in literature. The beads, besides facilitating the easy filtration, are exhibiting enhanced cumulative phosphate-adsorption nature of nanoZrO2 and Al-alginate. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) investigations are employed in characterizing the adsorbents. Of the various isotherm models analyzed to assess the nature of adsorption, Freundlich model provides the best correlation (R2 = 0.99 for nZrO2 and R2 = 0.99 for 'nZrO2-Al-alig'), indicating the heterogeneous and multi-layered adsorption process. Thermodynamic studies reveal the endothermic and spontaneous nature of sorption. Pseudo-second-order model of kinetics describes the adsorption well. Spent adsorbents can be regenerated with marginal loss of adsorption capacity until five cycles. The sorbents are successfully applied to remove phosphate from polluted lake water samples.

Sequential synergetic sorption analysis of Gracilaria Rhodophyta biochar toward aluminum and fluoride: A statistical optimization approach.

The present work proposes the synthesis of robust biochar from Gracilaria Rhodophyta red weeds for sequential removal of Al(III) and fluoride from wastewater. The sorption experiments have been modeled by preliminary optimization of operational parameters using 24 factorial statistical modeling. The model has estimated an optimum sequential synergetic removal of 44.5 mg/g of Al(III) and 2.1 mg/g of fluoride onto the biochar. FESEM, BET, XRD, EDX, and FTIR established the potentiality of biochar toward synergetic sorption of Al(III) and fluoride. The thermodynamic analysis projected that the adsorption is physisorption in nature. The adsorption of Al(III) and fluoride follows the Langmuir and Freundlich isotherm models, respectively, and the kinetic analysis established the pseudo-second-order deposition of Al(III) and fluoride ions. The synthesized adsorbent is regenerative enough and could achieve synergetic removal of Al(III) and fluoride ions from industrial- and groundwater-contaminated water bodies. PRACTITIONER POINTS: Biochar from seaweeds is explored in the sequential removal of Al(III) and F- ions. Statistical model is developed for % adsorption and tested for reliability by ANOVA. GRBC sorbed 44.5 and 2.1 mg/g of Al(III) and F- ions, respectively, at optimum levels. FESEM, EDX, XRD, and FTIR characterization confirm the potentiality of the GRBC. GRBC sorbed ⁓90% of Al(III) and F- ions from wastewater and is regenerative.

Extraction of Phosphate from Polluted Waters Using Calcium Alginate Beads Doped with Active Carbon Derived from A. aspera Plant as Adsorbent.

An adsorbent prepared by entrapping active carbon derived from the stems of Achyranthes aspera plant in the calcium alginate beads (CABAA) has been investigated for its adsorption nature towards the removal of phosphate by varying various physicochemical parameters. Surface morphological studies are made using FTIR, XRD, FESEM, and EDX. The sorption mechanism is analyzed using Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin adsorption isotherms. The adsorption kinetics is found to follow the pseudo-second-order model. Thermodynamic parameters are analyzed and found that the adsorption is endothermic and nonspontaneous in nature. The maximum amount of phosphate adsorbed onto CABAA is found to be 133.3 mg/g of active carbon and, furthermore, the adsorbent is highly selective. The methodology developed is successfully applied to polluted water samples.