Devlina Das

Recovery of rare earth metals through biosorption: An overview

Abstract Rare earth metals (REMs) are a series of 17 elements that have widespread and unique applications in high technology, power generation, communications, and defense industries. These resources are also pivotal to emergent sustainable energy and carbon alternative technologies. Recovery of REMs is interesting due to its high market prices along with various industrial applications. Conventional technologies, viz. precipitation, filtration, liquid-liquid extraction, solid-liquid extraction, ion exchange, super critical extraction, electrowinning, electrorefining, electroslag refining, etc., which have been developed for the recovery of REMs, are not economically attractive. Biosorption represents a biotechnological innovation as well as a cost effective excellent tool for the recovery of rare earth metals from aqueous solutions. A variety of biomaterials such as algae, fungi, bacteria, resin, activated carbon, etc., have been reported to serve as potential adsorbents for the recovery of REMs. The metal binding mechanisms, as well as the parameters influencing the uptake of rare earth metals and isotherm modeling are presented here. This article provides an overview of past achievements and current scenario of the biosorption studies carried out using some promising biosorbents which could serve as an economical means for recovering REMs. The experimental findings reported by different workers will provide insights into this research frontier.

Kinetics, equilibrium and thermodynamic studies on biosorption of Ag(I) from aqueous solution by macrofungus Pleurotus platypus

Reports are available on silver binding capacity of some microorganisms. However, reports on the equilibrium studies on biosorption of silver by macrofungi are seldom known. The present study was carried out in a batch system using dead biomass of macrofungus Pleurotus platypus for the sorption of Ag(I). P. platypus exhibited the highest silver uptake of 46.7 mg g(-1) of biomass at pH 6.0 in the presence of 200 mg L(-1) Ag(I) at 20°C. Kinetic studies based on fractional power, zero order, first order, pseudo-first order, Elovich, second order and pseudo-second order rate expressions have been carried out. The results showed a very good compliance with the pseudo-first order model. The experimental data were analyzed using two parameter isotherms (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Halsey), three parameter isotherms (Redlich-Peterson, Sips, Khan, Koble-Corrigan, Hill, Toth, Radke-Prausmitz, Jossens, Langmuir-Freundlich), four parameter isotherms (Weber-van Vliet, Fritz-Schlunder, Baudu) and five parameter isotherm (Fritz-Schlunder). Thermodynamic parameters of the biosorption (ΔG, ΔH and ΔS) were also determined. The present study confirmed that macrofungus P. platypus may be used as a cost effective efficient biosorbent for the removal of Ag(I) ions from aqueous solution.

Combined effects of sugarcane bagasse extract and synthetic dyes on the growth and bioaccumulation properties of Pichia fermentans MTCC 189.

Bioaccumulation of synthetic dyes viz. Acid Blue 93, Direct Red 28 and Basic Violet 3 by growing cells of yeast, Pichia fermentans MTCC 189 was investigated in growth media prepared from sugarcane bagasse extract. The maximum dye bioaccumulation was determined at pH 5.0 for all the dyes tested. Two kinetic models viz. Noncompetitive and Uncompetitive models were tested in order to determine the toxic effects of dyes on the specific growth rate of P. fermentans MTCC 189. Basic Violet 3 was found to be more toxic than the other two dyes. The combined effects of sugarcane bagasse extract and initial Basic Violet 3 dye concentrations on the specific growth rate and dye bioaccumulation efficiency of P. fermentans MTCC 189 was investigated and optimized using Response Surface Methodology (RSM). A 2(2) full factorial central composite design was successfully used for analysis of results. The optimum combination predicted via RSM confirmed that P. fermentans MTCC 189 was capable of bioaccumulating Basic Violet 3 dye upto 69.8% in the medium containing 10 mg/L of dye and 24 g/L sugar extracted from sugarcane bagasse.

Optimization of parameters for cerium(III) biosorption onto biowaste materials of animal and plant origin using 5-level Box-Behnken design: Equilibrium, kinetic, thermodynamic and regeneration studies

Abstract Response surface methodology (RSM) employing 5-level Box-Behnken design was used to optimize the biosorption of cerium(III) onto biowaste materials of animal and plant origin viz. prawn carapace (PC) and corn style (CS). Various process parameters viz. pH (A: 3.0–9.0), biomass dosage (B: 0.05–0.35 g/L), initial metal concentration (C: 50–350 mg/L), contact time (D: 2–6 h) and temperature (E: 20–60 °C) were chosen for optimization. A log transformation was suggested by the Box-Cox plot in the present case. A low p-value of

Sunlight mediated diesel degradation under saline conditions using ionic silver coated sand via nanoreduction: use of impregnated form of thiourea modified chitosan membranes for ex situ application.

The present research investigates the use of ionic silver coated sand dust (ISSD) for the sunlight mediated degradation of diesel under saline conditions. Sand dust was used as a template for reduction of silver ions by effective removal of chloride ions. Diesel degradation was estimated in terms of degradation (%), chloride removal, volume reduction and nanoparticle synthesis, respectively. The process was optimized using a 7-level Box-Behnken design. Among several factors, time (B), Tween 80 (C), ISSD dosage (D) and silver(I) concentration (F) were found to be most significant. Maximum diesel degradation 99.8% was obtained in a period of 14 h which was analyzed by gas chromatography. XPS analysis confirmed silver reduction as the underlying phenomena. TEM analysis and albeit first approximation method confirmed that enhanced degradation occurred due to physical contact between diesel components and ISSD. First order kinetic model exhibited the best fit. Light microscopy results showed the various stages in diesel degradation by a reduction in bubble size. Ex situ application was carried out using ISSD impregnated thiourea modified chitosan/PVA membranes by surface floatation technique for the remediation of diesel contaminated sea water. Complete diesel degradation was noted after 48 h of sunlight exposure.

Enhanced Zn(II) uptake using zinc imprinted form of novel nanobiosorbent and its application as an antimicrobial agent

We investigated the use of zinc imprinted of novel nanobiosorbent prepared from Candida rugosa to remove Zn(II) from aqueous solution. The nanobiosorbent was characterized by SEM, FTIR and XRD. Effects of various parameters including pH of the solution, adsorbent dosage, initial Zn(II) ion concentration and contact time on Zn(II) removal by the nanobiosorbents were investigated through batch process. Equilibrium data for Zn(II) removal was fitted to Langmuir isotherm model with an enhanced adsorption capacity of 275.48mg/g for zinc imprinted C. rugosa nanobiosorbent, compared to nonimprinted nanobiosorbent of 172.41 mg/g. Pseudo-second-order kinetic model was best fitted to predict the sorption kinetics for both the nanobiosorbents. AFM study revealed monolayer adsorption with thin film diffusion for Zn(II) removal. The antimicrobial activity of zinc imprinted nanobiosorbent was investigated against pathogenic yeasts viz. Candida albicans and Cryptococcus neoformans using agar well diffusion method.

Application of novel nanobiocomposites for removal of nickel(II) from aqueous environments: Equilibrium, kinetics, thermodynamics and ex-situ studies

The current study presents a novel approach for the removal of Ni(II) from aqueous environments using plant gum-based (PG) and clay-based (CL) nanobiocomposite (NBC) composed of ZnO nanoparticles and chitosan. Parameters like pH, contact time, temperature, initial metal concentration and adsorbent dosage were optimized. Under optimized conditions, maximum removal of Ni(II) was noted as 90.1% and 95.5% in the case of PG-NBC and CL-NBC, respectively. Equilibrium studies suggested a homogeneous mode of adsorption. Good linearity was observed for the pseudo-first order kinetic model, suggesting a physical mode of adsorption. Thermodynamic studies showed an endothermic and spontaneous nature of adsorption. The mechanism was further elucidated using SEM, EDX, AFM and FT-IR analysis. Ex-situ studies showed a maximum Ni(II) removal of 87.34% from electroplating wastewater using CL-NBC in column mode. Regeneration studies suggested that CL-NBC could be consistently reused up to 4 cycles.

Potentiality of yeast Candida sp. SMN04 for degradation of cefdinir, a cephalosporin antibiotic: kinetics, enzyme analysis and biodegradation pathway

A new yeast strain isolated from the pharmaceutical wastewater was capable of utilizing cefdinir as a sole carbon source for their growth in mineral medium. The yeast was identified and named as Candida sp. SMN04 based on morphology and 18S-ITS-D1/D2/D3 rRNA sequence analysis. The interaction between factors pH (3.0–9.0), inoculum dosage (1–7%), time (1–11 day) and cefdinir concentration (50–450 mg/L) was studied using a Box-Behnken design. The factors were studied as a result of their effect on cell dry weight (R1; g/L), extended spectrum β-lactamase (ESBL) assay (R2; mm), P450 activity (R3; U/mL) and degradation (R4; %). Maximum values of R1, R2, R3 and R4 were obtained at central values of all the parameters. The isolated yeast strain efficiently degraded 84% of 250 mg L−1 of cefdinir within 6 days with a half-life of 2.97 days and degradation rate constant of 0.2335 per day. Pseudo-first-order model efficiently described the process. Among the various enzymes tested, the order of activity at the end of Day 4 was noted to be: cytochrome P450 (1.76 ± 0.03) > NADPH reductase (1.51 ± 0.20) > manganese peroxidase and amylase (0.66 ± 0.15; 0.66 ± 0.70). Intermediates were successfully characterized by liquid chromatography–mass spectrometry. The opening of the β-lactam ring involving ESBL activity was considered as one of the major steps in the cefdinir degradation process. Fourier transform-infrared spectroscopy analysis showed the absence of spectral vibrations between 1766 and 1519 cm−1 confirming the complete removal of lactam ring during cefdinir degradation. The results of the present study are promising for the use of isolated yeast Candida sp. SMN04 as a potential bioremediation agent.

Adsorptive removal of nickel(II) ions from aqueous environments using gum based and clay based polyaniline/chitosan nanobiocomposite beads and microspheres: Equilibrium, kinetic, thermodynamics and ex-situ studies

The present study was carried out using gum (Ga) based and clay (MMT) based nanobiocomposite beads and microspheres composed of polyaniline NPs (PANI) and chitosan (Ch) as adsorbent for the removal of Ni(II) ions from aqueous environments. Under optimized conditions maximum Ni(II) removal 98.12% was exhibited by clay based nanobiocomposite (PANI-Ch-MMT) beads followed by gum based nanobiocomposite (PANI-Ch-Ga) beads (95.02%), PANI-Ch-MMT microspheres (85.12%) and PANI-Ch-Ga microspheres (75.23%). Equilibrium studies suggested a homogeneous mode of Ni(II) adsorption. Better applicability of pseudo-first order kinetic model suggested physisorption as the underlying phenomenon. Thermodynamic studies showed that adsorption was endothermic and spontaneous. The mechanism of adsorption by PANI-Ch-MMT and PANI-Ch-Ga beads was elucidated using SEM, EDX and FT-IR analyses. Ex-situ studies showed a maximum Ni(II) removal of 80.55% from mining wastewater using PANI-Ch-MMT beads in column mode. Regeneration studies suggested that PANI-Ch-MMT beads could be consistently reused up to five cycles.

Caffeine removal using pretreated dead yeast Trichosporon sp. VITLN01 as novel adsorbent

Dead biomass of yeast Trichosporon sp. VITLN01 pretreated with Tween 80, sodium dodecylsulfate (SDS) and NaOH were used as adsorbents for caffeine removal from aqueous solution. In batch system, maximum caffeine uptake was noted using Tween 80 treated adsorbent at pH 7.5 and adsorption equilibrium time was 3 h. The Langmuir, Freundlich and Temkin adsorption models were applied for mathematical description of adsorption equilibrium. Langmuir model was able to describe the adsorption equilibrium of caffeine on native and pretreated adsorbents. Thermodynamics studies indicated that caffeine adsorption process was spontaneous and exothermic in nature. FTIR analysis provided a detailed description of possible binding groups present in the adsorbents. SEM analysis revealed interesting changes in the surface texture of pretreated adsorbents before and after caffeine adsorption. Tween 80 treated adsorbent immobilized in PVA-alginate matrix was used to remove caffeine from coffee processing industrial wastewater in batch mode. The present study, also confirmed that immobilized Tween 80 treated dead biomass of yeast Trichosporon sp. VITLN01 may serve as efficient adsorbent for removal of caffeine from industrial wastewater.