Highly efficient simultaneous biosorption of Hg 2+ , Pb 2+ and Cu 2+ by Live yeast Yarrowia lipolytica 70562 following response surface methodology optimization: Kinetic and isotherm study

Adsorption characteristics and applications of andesite in removing some pollutants from wastewater

Andesite was employed to effectively extract mercury(II) in an aqueous solution. After evaluating its characteristics, andesite was characterized by applying modern techniques such as BET and TGA methods. The study employed SEM and TEM measurements to analyze the variation in the surface shape and crystallinity of the metal due to adsorption. Using the EDX process, the chemical composition, weight, and atomic percentage of each element of andesite were determined. FTIR techniques were also used to confirm the TEM-EDX findings. Zeta potential was estimated. Cycles of regeneration and desorption have been examined. 99.03% was the highest uptake percentage. Adsorbent quantity (0.0025-0.05) g/L, contact time (5-60) min, pH (2-10), temperature (25-60) °C, and dose (0.0027, 0.0044, 0.0125, 0.0155, and 0.0399) mg/L all affect the amount of removal that increases with the increase in contact time, pH, dose, and temperature but drops as the metal ion concentration rises. The ideal values for contact time, pH, metal ion concentration, dose, and temperature were found to be, respectively, 30 min, 0.0155 mg/l, 0.02 g/l, and 40 °C. The calculation of thermodynamic parameters, including ΔH, ΔG, and ΔS, was imperative in establishing that the mechanism of heavy metal adsorption on andesite was endothermic, exhibiting a physical nature that escalated with temperature rise. The Freundlich adsorption equation's linear form is matched by the adsorption of mercury(II) on andesite; constant n was 1.85, 1.06, 1.1, and 1.1, whereas the Langmuir constant qm was found to be 1.85, 2.41, 3.54, and 2.28 mg/g at 25-60 °C. Furthermore, adsorption follows a pseudo-second-order rate constant of (3.08, 3.24, 3.24, and 13) g/mg/min under identical temperature conditions, as opposed to a first-order rate constant of 4, 3, 2.6, and 2. Hg2+, NH4+, Cl-, Br-, NO3-, SO42-, Na+, K+, H2S, and CH3SH were all extracted from wastewater by this application.

Biofabricated yeast: super-soldier for detoxification of heavy metals

The advances in nanotechnology have shown enormous impacts in environmental technology as a potent weapon for degradation of toxic organic pollutants and detoxification of heavy metals. It is either by in-situ or ex-situ adaptive strategies. Mycoremediation of environmental pollutants has been a success story of the past decade, by employing the wide arsenal of biological capabilities of fungi. Recently, the proficiency and uniqueness of yeast cell surface alterations have encouraged the generation of engineered yeast cells as dye degraders, heavy metal reduction and its recovery, and also as detoxifiers of various hazardous xenobiotic compounds. As a step forward, recent trends in research are towards developing biologically engineered living materials as potent, biocompatible and reusable hybrid nanomaterials. They include chitosan-yeast nanofibers, nanomats, nanopaper, biosilica hybrids, and TiO₂-yeast nanocomposites. The nano-hybrid materials contribute significantly as supportive stabilizer, and entrappers, which enhances the biofabricated yeast cells' functionality. This field serves as an eco-friendly cutting-edge cocktail research area. In this review, we highlight recent research on biofabricated yeast cells and yeast-based biofabricated molecules, as potent heavy metals, toxic chemical detoxifiers, and their probable mechanistic properties with future application perspectives.

Optimization of Methyl Anthranilate Synthesis Process by Response Surface Methodology and Its Reaction Mechanism

In this paper, a unique process for the production of methyl anthranilate (MA) was investigated. The factors of the phthalimide/sodium hypochlorite/methanol molar ratio, reaction temperature, hydrolysis temperature, and water consumption on the yield and purity of MA were analyzed. Response surface methodology (RSM) was used to optimize conditions for the semi-batch synthesis process of MA. The best synthetic conditions for the formation of MA were reaction temperature 0.5 °C, hydrolysis temperature 70 °C and n(phthalimide)/n(sodium hypochlorite)/n(methanol) = 1:2.03:5.87, and water consumption m(H2O)/m(phthalimide) = 7.16:1. The yield of MA could reach 90% under the optimal conditions, which is more than 10% higher than that of the previous semi-batch process. Furthermore, the reaction mechanism was investigated by infrared spectroscopy analysis, and the mechanism of ester group formation and the structure of intermediate products are proposed. The byproduct of the reaction was studied by GC-MS analysis, a byproduct called 2-cyanobenzoic acid has been discovered. Therefore, an unprecedented reaction mechanism of the whole synthesis process is proposed.

A comprehensive assessment of Yarrowia lipolytica and its interactions with metals: Current updates and future prospective

The non-conventional yeast Yarrowia lipolytica has been popular as a model system for understanding biological processes such as dimorphism and lipid accumulation. The organism can efficiently utilize hydrophobic substrates (hydrocarbons and triglycerides) thereby rendering it relevant in bioremediation of oil polluted environments. The current review focuses on the interactions of this fungus with metal pollutants and its potential application in bioremediation of metal contaminated locales. This fungus is intrinsically equipped with a variety of physiological and biochemical features that enable it to tide over stress conditions induced by the presence of metals. Production of enzymes such as phosphatases, reductases and superoxide dismutases are worth a special mention. In the presence of metals, levels of inherently produced metal binding proteins (metallothioneins) and the pigment melanin are seen to be elevated. Morphological alterations with respect to biofilm formation and dimorphic transition from yeast to mycelial form are also induced by certain metals. The biomass of Y. lipolytica is inherently important as a biosorbent and cell surface modification, process optimization or whole cell immobilization techniques have aided in improving this capability. In the presence of metals such as mercury, cadmium, copper and uranium, the culture forms nanoparticulate deposits. In addition, on account of its intrinsic reductive ability, Y. lipolytica is being exploited for synthesizing nanoparticles of gold, silver, cadmium and selenium with applications as antimicrobial compounds, location agents for bioimaging and as feed supplements. This versatile organism thus has great potential in interacting with various metals and addressing problems related to their pollutant status.

Biosorption of hazardous waste from the municipal wastewater by marine algal biomass

Lead is one of the highly toxic heavy metals causes various diseases even at very lower concentrations to human and affects eco-system. It is mainly released into the water through industrial activities. Phytoremediation is useful to degrade, reduce, metabolize and assimilate lead from wastewater. In this study, Turbinaria ornata was collected from the sea and dried biomass was used for biosorption of heavy metals. Adsorption of heavy metal was maximum after 100 min incubation with alga powder at acidic pH (4.5). The interactive effects of lead concentration, contact times, pH, biomass concentration and agitation speed was evaluated by a two-level full factorial design. Initial lead concentration, agitation speed and biomass concentration were the most important variables affecting lead removal (p < 0.001) were selected for optimization using central composite rotatable design. Lead removal was found to be maximum (99.8%) in optimized conditions: initial lead 99.8 mg/L, 250 rpm agitation speed and 16.2 g/L biomass concentrations. Municipal wastewater was collected and lead concentration (0.013 mg/L) and physiochemical factors were analyzed. Algal biomass removed >98.5% lead form the wastewater within 10 min in an optimized condition. The present study confirmed the potential application of T. ornata for the removal of lead from contaminated environment.

Biosorption as a method of biowaste valorization to feed additives: RSM optimization

The aim of this work was to prepare an innovative microelemental feed additive for laying hens, based on waste biomass from the agricultural sector (alfalfa and goldenrod after CO₂ extraction in supercritical state). The process was optimized by Response Surface Methodology (RSM) and the most favourable enrichment conditions were selected for Cu(II), Mn(II) and Zn(II) ions: pH - 5, sorbate concentration of Cu(II), Mn(II), Zn(II) - 10.0 mg/L for alfalfa and 10.7 mg/L for goldenrod and biomass dose - 0.1 g/L. Physicochemical properties of biomass were studied and functional groups involved in the binding of Cu(II), Mn(II), Zn(II) ions were determined (mainly carboxylic and hydroxylic groups). An interesting and unique element of this work is the verification of the properties of prepared feed additives in conditions simulating the digestive tract of animals. The release of components in solutions simulating conditions in the intestine and stomach (pH 11 and pH 1) was tested (in vitro tests). The best desorption results were achieved at a strongly acidic pH which corresponds to the stomach environment: 9.80, 14.4% Cu(II), 69.0, 66.9% (Zn), 46.5, 31.9 Mn(II) for alfalfa and goldenrod, respectively. It was concluded that the biomass enriched with micronutrients in biosorption has the potential as a feed additive for sustainable agriculture.

Potentiality of living Bacillus pumilus SWU7-1 in biosorption of strontium radionuclide

Bacillus pumilus SWU7-1 was isolated from strontium ion (Sr(II))-uncontaminated soil, its biosorption potential was evaluated, and the effect of γ-ray radiation treatment on its biosorption was discussed. Domesticated under Sr(II) stress promoted the biosorption ability of B. pumilus to Sr(II), and the biosorption efficiency increased from 46.09% to 94.69%. At a lower initial concentration, the living bacteria had the ability to resist the biosorption of Sr(II). The optimal initial concentration range was 54-130 mg/L. The biosorption profile was better matched by Langmuir than Freundlich model, showing that the biosorption process of Sr(II) by the experimental strain was closer to the surface adsorption. According to Langmuir model, the maximum biosorption capacity of B. pumilus on Sr (II) was 299.4 mg/g. During the bacterial growth in the biosorption process, the changes in biosorption capacity and efficiency can be divided into two phases, and a pseudo-second-order model is followed in each phase. There was no significant difference in the biosorption efficiency of bacteria with different culture time after γ-ray radiation, and all of them were above 90%, which showed that B. pumilus had significant radiation resistance under experimental conditions. This study emphasized the potential application of B. pumilus in the treatment of radioactive Sr(II) pollution by biosorption.

Ultrasound wave assisted removal of Ceftriaxone sodium in aqueous media with novel nano composite g-C3N4/MWCNT/Bi2WO6 based on CCD-RSM model

The aim of this study was ultrasound assisted removal of Ceftriaxone sodium (CS) based on CCD model. Using sonochemical synthesized Bi₂WO₆ implanted on graphitic carbon nitride/Multiwall carbon nanotube (g-C₃N₄/MWCNT/Bi₂WO₆). For this purpose g-C₃N₄/MWCNT/Bi₂WO₆ was synthesized and characterized using diverse approaches including XRD, FE-SEM, XPS, EDS, HRTEM, FT-IR. Then, the contribution of conventional variables including pH, CS concentration, adsorbent dosage and ultrasound contact time were studied by central composite design (CCD) under response surface methodology (RSM). ANOVA was employed to the variable factors, and the most desirable operational conditions mass provided. Drug adsorption yield of 98.85% obtained under these defined conditions. Through conducting five experiments, the proper prediction of the optimum point were examined. The respective results showed that RSD% was lower than 5% while the t-test confirmed the high quality of fitting. Langmuir isotherm equation fits the experimental data best and the removal followed pseudo-second order kinetics. The estimation of the experimentally obtained maximum adsorption capacities was 19.57 mg.g^- of g-C₃N₄/MWCNT/Bi₂WO₆ for CS. Boundary layer diffusion explained the mechanism of removal via intraparticle diffusion.

MOFs for the treatment of arsenic, fluoride and iron contaminated drinking water: A review

Over the last few decades, the global pollution of surface and groundwater poses a serious threat not only to human beings but also towards aquatic lives due to the presence of emerging contaminants. Among the others, the presence of arsenic, fluoride, and iron are considered as the most common toxic pollutants in water bodies. The emergence of metal organic frameworks (MOFs) with high porosity and surface area is represented as significant inclusion into the era of entrapping contaminants present in drinking water. In the present review article, an in-depth insight is provided on the recent developments in the removal of arsenic, fluoride, and iron from drinking water using MOFs. Various aspects related to the synthesis, latest technologies adopted for the modifications in the synthesis process and advanced applications of MOFs for the removal of such contaminants are explicitly discussed. A detailed insight was provided to understand the mechanism of various interactions of MOFs with arsenic and fluoride. With respect to arsenic, fluoride, and iron removal the ultrastructural morphology of MOFs is assessed based on different molecular arrangements. Further, commercial aspects of various MOFs are presented in order to highlight the process feasibility. Finally, various perspectives and challenges involved in process scale up are comprehensively narrated with an aspiration of futuristic developments. The paper will be beneficial to the readers for acquiring a piece of in-depth knowledge on MOFs and its various synthesis approaches along with remarkable achievements for the removal of arsenic, fluoride, and iron from contaminated drinking water.

Simultaneous removal of Pb2+, Cu2+ and Cd2+ ions from wastewater using hierarchical porous polyacrylic acid grafted with lignin

In PAA-g-lignin, phase separation, caused by the difference in expansion properties between lignin and polyacrylic acid, is used to build a porous hydrogel. In this study, PAA-g-APL was produced by grafting polyacrylic acid with acid-pretreated alkali lignin. Acid-pretreated alkali lignin acts as a hierarchical pore-forming agent that enhances the simultaneous adsorption capacities for Pb²⁺, Cu²⁺ and Cd²⁺ ions from wastewater. Notably, PAA-g-APL acted as a selective adsorbent for Pb²⁺ ions has an excellent selective removal coefficient α (20.22) in contaminated wastewater contained Cu²⁺ ions. Its molar partition coefficient for Pb²⁺ ions (68 %) is higher than that for either Cu²⁺ ions (28.6 %) or Cd²⁺ ions (3.4 %). At equilibrium, the total adsorption capacities of PAA-g-APL for Pb²⁺, Cu²⁺ and Cd²⁺ were 1.076 mmol g^-1, 0.3233 mmol g^-1 and 0.059 mmol g^-1, respectively. The experimental kinetic data fitted well to a pseudo-second order model and to an intra-particle-diffusion model. The Freundlich isotherm model gave the best fit with the experimental equilibrium data. The ΔG° for PAA-g-APL is < 0, indicating that the adsorption of heavy metal ions is a spontaneous process. This study provides a highly promising candidate for the treatment of wastewater contaminated with a mixture of heavy metals.

Fabrication of ultrasound-mediated tunable graphene oxide nanoscrolls

In this work, a cost-effective and facile method was adopted for the fabrication of graphene oxide nanoscrolls (GONS) by low frequency (20 kHz) ultrasonication with tunable dimensions. The graphene oxide (GO) was synthesized by modified Hummer's method using synthetic graphite as a base material. Later, GO suspension (0.05 g L^-1) were made using methanol as solvent and subjected to different ultrasonication conditions. It was found that GO sheets curls themselves into nanoscrolls by overcoming the energy barrier for scrolling with the help of bubble cavitation energy provided by ultrasonication. Also, the effect of ultrasonication power (100-150 W) for irradiation time (0.5-3 h) over the GONS dimensions were investigated. The spiral wounded GONS structures were shown using electron microscopy. Raman Spectroscopy, Thin-film X-Ray Diffraction, Energy Dispersive X-Ray, FT Infrared Spectroscopic analysis were also done to endorse GONS formation. Factors affecting GONS formation such as sonication power and solvent selection were studied as scrolling of GO sheets are strongly dependent on sonication parameters and solvent characteristics. It was found that GONS length varies inversely with irradiation time for identical power density. Also, a solvent with relatively large Hansen solubility parameter, lower dipole movement and less negative value of zeta potential support GONS formation of longer length. Raman analysis overlays the rapid oxygen-defect site cleavage mechanism. The obtained GONS unlocks further developments in various engineering applications like adsorption, drug delivery and filtration membrane.

Electrostatically controlled plasmonic effects of gold nanoparticles with indigo-carmine functionation for rapid and straightforward colorimetric detection of Cu2+ ions

A colorimetric sensor is fabricated for effective on-site monitoring of Cu²⁺ ions content based on the distance-dependent optical properties of gold nanoparticles-polyvinyl alcohol-citrate (Au-NPs-PVA-Cy) which plasmonic effect electrostatically was controlled by PVA-Cy stabilizing indigo-carmine (IC) functionalizing. The surface-modified gold nanoparticles were extremely stable with a strong affinity toward Cu²⁺ ions. Citrate ion was employed as a cross-linking agent for pairs of Au-NPs-PVA-Cy and IC for stabilizing coordination between Cu²⁺ ion and IC. The active materials were characterized by UV-Vis, SEM, DLS, XRD, FT-IR, and EDS analyses. The sensor response toward Cu²⁺ ion was found to be linear in the range of 0.0974 to 3.27 μM with the limit of detection and quantification values of 0.021 and 0.07 μM, respectively. The sensor represents good sensitivity and stability, promisingly suggesting this device for the accurate and repeatable determination of Cu²⁺ in real water samples. The effect of different foreign ions on the selectivity of the sensor was checked. The sensor has a long shelf life in comparison to other similar colorimetric sensors. Also, it shows a repeatable response with RSD% of 2.02%. Thus, the sensing of Cu²⁺ ions based on the electrostatically control plasmonic of Au-NPs-PVA-Cy was developed with proper signaling based on the color change from dark blue to light blue as readily seen by the naked eye. Furthermore, the efficient environmental applicability of this simple and rapid determination of the Cu²⁺ sensor is proved.

Synthesis and application of hydrazono-imidazoline modified cellulose for selective separation of precious metals from geological samples

A new hydrazono-imidazoline modified cellulose (HIMC) was synthesized for selective recovery of Pt(IV), Pd(II) and Au(III) from geological samples. Cellulose was oxidized by periodate and was further functionalized with hydrazono-imidazoline moieties to afford N-donor chelating fibers. Scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), N₂ physisorption, elemental analysis, and energy-dispersive X-ray spectroscopy (EDX) were used for characterization. Introducing the hydrazono-imidazoline groups at the surface of cellulose fibers did not alert their ordered structure and crystallinity, as indicated by XRD and SEM results. Factors affecting the adsorption were systematically investigated. Under the optimized conditions, the HIMC sorbent exhibited high adsorption capacities of 105, 88 and 75 mg g^-1 for Pt(IV), Pd(II) and Au(III), respectively. Besides, the metal ion adsorption process fitted by pseudo-second-order kinetic model and Langmuir adsorption isotherm. These results highlight the applicability of this carbohydrate-based sorbent for the selective recovery of precious metals from various matrices.

Industrial waste materials as adsorbents for the removal of As and other toxic elements from an abandoned mine spoil heap leachate: a case study in Asturias

The purpose of this study is to determine the capacity of four industrial waste materials originate from steelmaking processes and from gas treatment at a thermal power plant to remove As and other contaminants from a leachate from the spoil heap of an abandoned mercury mine. Arsenic removal is faster in the first minutes, then increases only slightly over time reaching equilibrium in 8 hours. As removal efficiency increased with increasing adsorbent concentration. As removal efficiency was found to be 82.7%, 71%, 37.2% and 27.2% for EA, FA, HA and G, respectively, when employing 80 g/dm³ of adsorbent concentration. The main mechanism of As removal appears to be the results show that Hg and Pb are completely removed using low concentrations of adsorbents regardless of the waste material used in the treatment. FA removed more than 82% of other toxic elements such as Ni, Cu and Cd. EA is the most effective byproduct of the four employed in this study for removing pollutants, while G is the least effective. The present study shows it is possible to carry out an efficient and economical treatment of mine leachate using these byproducts.

Adsorption of low concentrations of bromide ions from water by cellulose-based beads modified with TEMPO-mediated oxidation and Fe(III) complexation

Due to strong activity, it is very difficult to remove low concentrations of bromide in medical wastewater by traditional method, thus highly effective and greener adsorbents should be utilized to design. In this work, the cellulose beads (CBs) were modified by the TEMPO-mediated oxidation and then bonded with Fe³⁺ to fabricate Fe(III)-complexed carboxylated cellulose beads (Fe-CCBs) adsorbents. Structure and properties of Fe-CCBs were analyzed using Energy dispersive spectrum (EDS), Scanning electron microscopy (SEM), Fourier transform infrared spectrum (FT-IR), total acidity and basicity groups, X-ray diffraction (XRD), N₂ adsorption-desorption and Thermogravimetric (TGA). Moreover, batch adsorption experiments showed that the adsorption of Br^- was better consistent with general-order kinetic model and Liu isotherm model, which could also further clarify the adsorption process mechanism. Meanwhile, the results revealed that removal of Br- was a spontaneous exothermic process and was more suitable to be carried out under neutral or acidic conditions. Furthermore, the mechanism of adsorption behavior of bromide ions on Fe-CCBs was based on a combination of electrostatic attraction and outer-sphere complexation. The results of this study can provide guidance for the design of novel material adsorbents and the removal of harmful anions from aqueous solutions.

Bioaccumulation and distribution of cadmium by Burkholderia cepacia GYP1 under oligotrophic condition and mechanism analysis at proteome level

Bacteria have been applied for the bioremediation of cadmium-contaminated environment. Less is known about the bioaccumulation of high concentration of Cd over time under the oligotrophic environment. Burkholderia cepacia GYP1, which was isolated from multiple heavy metal contaminated farmland, was studied for its bioaccumulation mechanism of Cd under oligotrophic condition. GYP1 possessed highly accumulation capacity for cadmium reaching 116 mg Cd/g biomass (dry weight). ATR-FTIR, electron microscopy, flow cytometry along with subcellular fraction demonstrated that the uptake and distribution of cadmium varied with the increased amount of cadmium of GYP1 cell during the 7-day treatment time: the accumulation of cadmium was mainly on the outer membrane at the beginning (within 1 day), and the intracellular cadmium kept increased and held stable after 2 days, after that, the increased amount of cadmium mainly located extracellularly, related to the secreted EPS. Further mechanism analysis of bioaccumulation of Cd by GYP1 based on iTRAQ-based proteomics showed that Cd(II) could trigger the up-regulation of the Cd²⁺/Zn²⁺-exporting ATPase, type VI protein secretion systems, and glutathione-S-transferase that are related to cadmium response, which may contribute to maintain the intracellular cadmium homeostasis. In summary, the immobilization of Cd(II) by B. cepacia GYP1 contains three steps:(1) fast immobilization of Cd(II) on the cell surface coordinated with functional groups, (2) transport of Cd(II) to cells and accumulation in cytoplasm, and (3) efflux of intracellular Cd(II) depended on energy and the entrapped or adsorbed of extracellular Cd(II) by EPS. Our study provided the understanding of the cadmium accumulation process of B. cepacia GYP1 under oligotrophic condition, which would be helpful in bioremediation of natural cadmium contaminated environment.

Preparation and characterization of poly aniline modified chitosan embedded with ZnO-Fe3O4 for Cu(II) removal from aqueous solution

Poly aniline modified chitosan embedded with ZnO/Fe₃O₄ nanocomposites were synthesized using a precipitation method and applied to the removal of Cu(II) from aqueous solution. The synthesized nanocomposite was characterized by FT-IR, XRD, FESEM, TEM, EDS, TGA, BET and zeta-potential analyses. The adsorption batch experiments were conducted as a function of five effective parameters including pH, contact time, initial concentration of copper, temperature, and adsorbent dosage using a central composite design (CCD) in response surface methodology (RSM). Contour and surface plots were used to determine the interaction effects of main factors and optimum conditions of process. The regression equation coefficients were calculated and the data confirmed the validity of second-order polynomial equation for the removal of Cu(II) with novel absorbent. Analysis of variance (ANOVA) showed a high coefficient of determination value (R²) for copper removal being 0.99. The optimum level of the pH, temperature, initial concentration of copper, adsorbent dosage and contact time for maximum Cu(II) removal (94.51%) were found to be 6.5, 31 °C, 82 mg L^-1, 0.81 g L^-1, and 51 min, respectively. It was confirmed from XPS and EDS analyses that heavy metal ions were present on the surface of nanocomposite after adsorption. The adsorption equilibrium data fitted well with the Langmuir isotherm model and the adsorption process followed the pseudo-second-order and intra-particle diffusion kinetic model. The saturated adsorption capacity is found to be 328.4 mg/g. Thermodynamics analysis suggests that the adsorption process is endothermic, with increasing entropy and spontaneous in nature. Further recycling experiments show that nanocomposite still retains 95% of the original adsorption following the 5th adsorption-desorption cycle. The effects of coexist cation ions on the adsorption of Cu(II) was also investigated under optimal condition. All the results demonstrate that nanocomposite is a potential recyclable adsorbent for hazardous metal ions in wastewater.

Optimization of heavy metal biosorption onto freshwater algae (Chlorella coloniales) using response surface methodology (RSM)

In this study, the interaction of the initial metal concentration, time of reaction and Chlorella coloniales algae dose were taken for the biosorption of Cr, Cd, Co, Fe and As from aqueous solutions using the Box-Behnken design. The regression equation coefficients were calculated and the data confirmed the validity of second-order polynomial equation for the removal of Cr, Cd, Co, Fe and As with Chlorella coloniales algae. Analysis of variance (ANOVA) showed a high coefficient of determination value (R²) for Cr, Cd, Co, Fe, and As, being respectively 0.998, 0.998, 0.995, 0.998 and 0.994. Heavy metal biosorption increased with the increase in time of reaction from 30 h to 100 h then smoothly steadily decreased. The biosorption capacity of Chlorella coloniales increased when initial Cd concentration was increased from 5 to 12 mg/L, and then no change was seen with further increasing in initial Cd concentration. At low concentrations of heavy metal, Chlorella coloniales showed its effectiveness for Cr, Co, Fe and As bioaccumulation, but at high concentrations of heavy metal bioaccumulation efficiency decreased Under optimal value of process parameters, maximum efficiencies for the removal of Cr, Cd, Co, Fe, and As were 97.8, 97.05, 95.15, 98.6 and 96.5% respectively. The results of the present study suggest that use of C. Coloniales algae can be a good alternative to the current expensive methods of removing heavy metals from aqueous solution.

Ultrasound wave assisted adsorption of congo red using gold-magnetic nanocomposite loaded on activated carbon: Optimization of process parameters

In this study, gold-magnetic nanocomposite in the presence of ultrasound wave assisted was synthesized and loaded on activated carbon (Au-Fe₃O₄-NCs-AC) by simple, fast and low-cost process. This novel material was applied for ultrasound assisted adsorption of congo red (CR) as model of toxic and even carcinogenic substance from aqueous solution. The detail of morphology and identity of Au-Fe₃O₄-AC was characterized by SEM and TEM techniques and correlation among response to variables such as pH (2-10), adsorbent mass (0.005-0.025 g), initial CR concentration (10-30 mg L^-1) and ultrasound time (2-6 min) was investigated by response surface methodology (RSM) under central composite design (CCD). Analysis of variance (ANOVA) exhibit a high R² value of 0.999 and confirm suitability of constructed second-order regression model for excellent evaluation and prediction of the experimental data. The interaction and main factor and optimum conditions of the under study process were determined from response surface plots based on desirability function. The maximum CR adsorption were achieved at pH of 4, 15 mg L^-1 of CR, 0.017 g of Au-Fe₃O₄-AC and 5 min sonication which owing to 99.49% removal efficiency is highly recommended for future CR removal from different matrixes. Adsorption kinetic follow second-order rate expression in combination to inter particle diffusion and equilibrium adsorption data best represented by the Langmuir isotherm with maximum mono-layer adsorption capacity of 43.88 mg g^-1.

Progress and prospect of adsorptive removal of heavy metal ions from aqueous solution using metal-organic frameworks: A review of studies from the last decade

The efficient removal of heavy metals (HMs) from the environment has become an important issue from both biological and environmental perspectives. Recently, porous metal-organic frameworks (MOFs), combining central metals and organic ligands, have been proposed as promising materials in the capture of various toxic substances, including HMs, due to their unique characteristics. Here we review recent progress in the field of water remediation from the perspective of primary HMs (including divalent metals and variable-valent metals) in water pollution and the corresponding MOFs (including virgin and modified MOFs, magnetic MOFs composites and so on) that can remove these metals from water. The reported values of various MOFs for adsorption of heavy metal ions were 8.40-313 mg Pb(II) g^-1, 0.65-2173 mg Hg(II) g^-1, 3.63-145 mg Cd(II) g^-1, 14.0-127 mg Cr(III) g^-1, 15.4-145 mg Cr(VI) g^-1, 49.5-123 mg As(III) g^-1, and 12.3-303 mg As(V) g^-1. The main adsorption mechanisms associated with these processes are chemical (including coordination interaction, chemical bonding and acid-base interactions) and physical (including electrostatic interaction, diffusion and van der Waals force) adsorption, which were discussed in detailed. Further efforts should be made towards expanding the repertoire of MOFs that effectively remove multiple targeted HMs, as well as exploring possible applications of MOFs in the removal of HMs from non-aqueous environments.

Photoinduced reduction of high concentration Hg(II) to Hg2Cl2 from acid wastewater with the presence of fulvic acid under anaerobic conditions

In order to recover mercury from high concentration Hg(II) acid wastewater, UV irradiation was used to reduce Hg(II) to Hg₂Cl₂ with the presence of fulvic acid and chloride ion. When simulated wastewater with Hg(II) concentration of 1000 mg L^-1 was treated, > 90% of Hg(II) removal efficiency was achieved under the condition of extra Cl^- dosage of 5 g L^-1, FA dosage of 2 g L^-1, pH of 3.0 and 120 min of UV irradiation. Kinetics study showed that the photoreduction process could be well described by pseudo-first order kinetic mode, and the Hg(II) reduction rate was tested to be 0.0422 min^-1. Characterization results indicated that FA-Hg(II) complexes were firstly formed and then broken down into smaller molecules after the UV treatment, in which process highly reductive species (i.e. COO, COOH) were produced. These reductive species mediated the reduction of Hg(II). With the presence of Cl^-, Hg₂Cl₂ was practically the only detected Hg-based product in the photoreduction process. This technique was also employed to treat COD_Cr analysis wastewater (initial Hg(II) concentration > 1000 mg L^-1). With 90 min of reaction, most of the Hg(II) was removed from the system leaving less than 30% that could be further treated by chemical participation or adsorption method.

Recent advances in conventional and contemporary methods for remediation of heavy metal-contaminated soils

Remediation of heavy metal-contaminated soils has been drawing our attention toward it for quite some time now and a need for developing new methods toward reclamation has come up as the need of the hour. Conventional methods of heavy metal-contaminated soil remediation have been in use for decades and have shown great results, but they have their own setbacks. The chemical and physical techniques when used singularly generally generate by-products (toxic sludge or pollutants) and are not cost-effective, while the biological process is very slow and time-consuming. Hence to overcome them, an amalgamation of two or more techniques is being used. In view of the facts, new methods of biosorption, nanoremediation as well as microbial fuel cell techniques have been developed, which utilize the metabolic activities of microorganisms for bioremediation purpose. These are cost-effective and efficient methods of remediation, which are now becoming an integral part of all environmental and bioresource technology. In this contribution, we have highlighted various augmentations in physical, chemical, and biological methods for the remediation of heavy metal-contaminated soils, weighing up their pros and cons. Further, we have discussed the amalgamation of the above techniques such as physiochemical and physiobiological methods with recent literature for the removal of heavy metals from the contaminated soils. These combinations have showed synergetic effects with a many fold increase in removal efficiency of heavy metals along with economic feasibility.

Mild synthesis of a Zn(II) metal organic polymer and its hybrid with activated carbon: Application as antibacterial agent and in water treatment by using sonochemistry: Optimization, kinetic and isotherm study

In this work, a room temperature and short method (30min) for synthesis of nanosized rod-like metal organic polymer (MOP) has been described. Reaction of 1,4-phenylenedioxy diacetic acid with zinc salt leads to the formation of [Zn(C₁₀H₈O₆)(H₂O)₄]_n and subsequently was loaded on activated carbon following sonication and structurally characterized by FTIR, SEM, EDX and XRD analysis. The combination of this new composite with sonication was applied for rapid and efficient adsorption of Bromocresol Purple (BCP). Effects of initial BCP concentration, mass of adsorbent and sonication time on response were investigated and optimized by central composite design (CCD). Analysis of variation (ANOVA) was adapted to experimental data to find best optimum conditions which was set at 15.22mgL^-1, 2.41min, 0.02g and 0.009mg for initial BCP concentration, sonication time and adsorbent mass, respectively. Conduction of similar experiments at specified condition permit achievement of 98.69% removal percentage. 1,4-phenylenedioxy diacetic acid and Zn(NO3)₂.4H₂O which have applied for preparation of MOP are interesting antibacterial properties and accordingly MOP was screened in vitro for their antibacterial actively against Proteus vulgaris bacteria and experimental results reveal this MOP was able to inhibit growth of the tested bacteria. The experimental data were best fitted by pseudo-second order and Langmuir for kinetic model and the adsorption equilibrium isotherm, respectively.

Isotherms and kinetic study of ultrasound-assisted adsorption of malachite green and Pb2+ ions from aqueous samples by copper sulfide nanorods loaded on activated carbon: Experimental design optimization

Copper sulfide nanorods loaded on activated carbon (CuS-NRs-AC) was synthesized and used for simultaneous ultrasound-assisted adsorption of malachite green (MG) and Pb²⁺ ions from aqueous solution. Following characterization of CuS-NRs-AC were investigated by SEM, EDX, TEM and XRD, the effects of pH (2.0-10), amount of adsorbent (0.003-0.011g), MG concentration (5-25mgL^-1), Pb²⁺ concentration (3-15mgL^-1) and sonication time (1.5-7.5min) and their interactions on responses were investigated by central composite design (CCD) and response surface methodology. According to desirability function on the Design Expert optimum removal (99.4%±1.0 for MG and 68.3±1.8 for Pb²⁺ions) was obtained at pH 6.0, 0.009g CuS-NRs-AC, 6.0min mixing by sonication and 15 and 6mgL^-1 for MG and Pb²⁺ ions, respectively. High determination coefficient (R²>0.995), Pred-R²-value (>0.920) and Adju-R²-value (>0.985) all are good indication of best agreement between the experimental and design modelling. The adsorption kinetics follows the pseudo-second order model and adsorption isotherm follows the Langmuir model with maximum adsorption capacity of 145.98 and 47.892mgg^-1 for MG and Pb²⁺ ions, respectively. This adsorbent over short contact time is good choice for simultaneous removal of large content of both MG and Pb²⁺ ions from wastewater sample.

Multistage optimizations of slow pyrolysis synthesis of biochar from palm oil sludge for adsorption of lead

This research investigated the removal of lead (Pb²⁺) by a novel biochar derived from palm oil sludge (POS-char) by slow pyrolysis. Multistage optimizations with central composite design were carried out to firstly optimize pyrolysis parameters to produce the best POS-char for Pb²⁺ removal and secondly to optimize adsorption conditions for the highest removal of Pb²⁺. The optimum pyrolysis parameters were nitrogen flowrateof30mLmin^-1, heating rateof10°Cmin^-1, temperatureof500°C and timeof30min. The optimum Pb²⁺ adsorption conditions were concentrationof200mgL^-1, timeof60min, dosageof0.3g and pH of 3.02. The various functional groups within POS-char played a vital role in Pb²⁺ uptake. Regeneration was demonstrated to be feasible using hydrochloric acid. Adsorption equilibrium was best described by Freundlich model. At low concentration range, adsorption kinetic obeyed pseudo-first-order model, but at high concentration range, it followed pseudo-second-order model. Overall, the results highlighted that POS-char is an effective adsorbent for Pb²⁺ removal.

Co-immobilization of glucose oxidase and catalase in silica inverse opals for glucose removal from commercial isomaltooligosaccharide

In this work, glucose oxidase (GOD) and catalase (CAT) were co-immobilized on novel silica inverse opals (IO-SiO₂) through sol-gel process. The immobilized bi-enzyme system named GOD/CAT@IO-SiO₂ was successfully fabricated and characterized. Morphology characterization indicated that GOD/CAT@IO-SiO₂ had hierarchical porous structure, and the pore diameter of macroporous and mesoporous were 500±50nm and 6.8nm, respectively. The macrospores were connected through windows of 100±30nm. The results of stability tests indicated that both acid (or base) resistance and thermal tolerance of GOD/CAT@IO-SiO₂ were improved. When GOD/CAT@IO-SiO₂ was used to remove glucose from commercial isomaltooligosaccharide (IMO), the immobilized bi-enzyme system exhibited the good performance. The removal efficiency of glucose reached up to 98.97% under the conditions of GOD/CAT activity ratio of 1:30, the amount of enzyme of 68.8mg, reaction time of 9.39h, reaction temperature of 35.2°C and pH of 7.05. After reused 6 times, 79.19% of removal efficiency could be still retained. The present work demonstrates that the immobilized bi-enzyme (GOD/CAT@IO-SiO₂) is not only a very promising system for glucose removal but also has great potential for applications in production of gluconic acid, preparation of biosensors, enzyme bioreactors, etc.