Biosorption Of Cr Research Articles

Biosorption of Cr(VI) Using Cellulose Nanocrystals Isolated from the Waterless Pulping of Waste Cotton Cloths with Supercritical CO2: Isothermal, Kinetics, and Thermodynamics Studies.

In the present study, supercritical carbon dioxide (scCO2) was utilized as a waterless pulping for the isolation of cellulose nanocrystals (CNCs) from waste cotton cloths (WCCs). The isolation of CNCs from the scCO2-treated WCCs’ fiber was carried out using sulphuric acid hydrolysis. The morphological and physicochemical properties analyses showed that the CNCs isolated from the WCCs had a rod-like structure, porous surface, were crystalline, and had a length of 100.03 ± 1.15 nm and a width of 7.92 ± 0.53 nm. Moreover, CNCs isolated from WCCs had a large specific surface area and a negative surface area with uniform nano-size particles. The CNCs isolated from WCCs were utilized as an adsorbent for the hexavalent chromium [Cr(VI)] removal from aqueous solution with varying parameters, such as treatment time, adsorbent doses, pH, and temperature. It was found that the CNCs isolated from the WCCs were a bio-sorbent for the Cr(VI) removal. The maximum Cr(VI) removal was determined to be 96.97% at pH 2, 1.5 g/L of adsorbent doses, the temperature of 60 °C, and the treatment time of 30 min. The adsorption behavior of CNCs for Cr(VI) removal was determined using isothermal, kinetics, and thermodynamics properties analyses. The findings of the present study revealed that CNCs isolated from the WCCs could be utilized as a bio-sorbent for Cr(VI) removal.

Effective kinetic modeling and phycoremediation of Cr(IV) ions from tannery effluent by using microalgae – Chlamydomonas moewusii, Auxenochlorella pyrenoidosa, Scenedesmus sp.

Chromium is a harmful heavy metal that is often found in tannery effluent. It is potentially toxic in nature and also acts as an anthropogenic source, so chromium ion is considered to be an environmental contaminant. The toxic effluents are generally treated in the process of remediation by using micro or macro-algae called “Phycoremediation” and it has shown effective cleanup approaches. The present study deals with the phycoremediation of chromium ion polluted effluent in Ambur tanneries. The isolated microalgae were collected from the estuary near the industrial site, which was observed for the preliminary metal tolerance activity then morphologically identified with the help of a compound microscope and they are named SMA1, SMA2, and SMA3. The taxonomical examination reveals that SMA1 is found to be 98.66% similar to Chlamydomonas moewusii, SMA2 was 99.24% similar to Scenedesmus sp., and SMA3 was 98.88% similar with Auxenochlorella pyrenoidosa. The identified microalgae were growing in the specific growth media BG11 and tannery effluent was supplemented along with the culture media to determine the growth rate, biomass production, and total protein content, which also regulates the potential bio-sorption and absorption rate of Cr(VI) ion. The activity of biosorption was seen to be 90% for C. moewusii (SMA1), 65% for Scenedesmus sp. (SMA2), and 80% for A. pyrenoidosa (SMA3), which showed the potential activity in phycoremediation process. Adsorption mechanism is studied by kinetic modeling of data experimentation which is bound with pseudo-first-order kinetics and pseudo-second-order kinetics; this mechanism exposed the adsorption capability of microalgae. The outcome of this study shows that the microalgae species are considered to be the most effective biosorbents for removing Cr(VI) ions from the tannery effluent.

Bioreduction and bioremoval of hexavalent chromium by genetically engineered strains (Escherichia coli MT2A and Escherichia coli MT3).

The number of studies on the removal of hazardous metals from water using genetic engineering technologies is growing. A high rate of metal ion removal from the environment is ensured, particularly through the expression of cysteine and thiol-rich proteins such as metallothioneins in bacterial cells. In this study, we used recombinant strains created by cloning the human metallothioneins MT2A and MT3 into Escherichia coli Jm109 to assess the removal and reduction of hexavalent chromium (Cr(VI)) from aqueous solutions. MT2A was the most effective strain in both Cr(VI) removal (89% in 25mg/L Cr(VI)) and Cr(VI) reduction (76% in 25mg/L Cr(VI)). The amount of Cr adsorbed per dry cell by the MT2A strain was 22mg/g. The biosorption of total Cr was consistent with the Langmuir isotherm model. Scanning electron microscope (SEM) images revealed that the morphological structures of Cr(VI)-treated cells were significantly damaged when compared to control cells. Scanning transmission electron microscope (STEM) images showed black spots in the cytoplasm of cells treated with Cr(VI). Shifts in the Fourier transform infrared spectroscopy analysis (FTIR) spectra of the cells treated with Cr(VI) showed that the groups interacting with Cr were hydroxyl, amine, amide I, amide II, phosphoryl and carbonyl. When all of the experimental data was combined, it was determined that both MT2A and MT3 were effective in removing Cr(VI) from aqueous solutions, but MT2A was more effective, indicating that MT2A may be employed as a biotechnological tool.

Biosorption and bioreduction of Cr (VI) by rice husk and toxicity analysis on zebrafish embryos

Biosorption and bioreduction of Cr (VI) by rice husk and toxicity analysis on zebrafish embryos

Chemical Modification of Teff Straw Biomass for Adsorptive Removal of Cr (VI) from Aqueous Solution: Characterization, Optimization, Kinetics, and Thermodynamic Aspects

Teff straw, a by-product of Teff, mainly available in Ethiopia, has not been studied much for biosorbent production. The present study has investigated the effects of modification and optimization of process parameters (viz., concentration of modifying agent (H3PO4 and KOH), modifying temperature, and modifying time) on the Cr (VI) removal efficiency of using chemically activated Teff straw biosorbent by RSM followed by BBD. The maximum Cr (VI) removal was obtained using an H3PO4-modified Teff straw biosorbent of 92.5% with 2 M concentration of the modifying agent, 110°C, and 4 h. Similarly, maximum Cr (VI) removal using KOH-modified Teff straw biosorbent of 95.2% was obtained with 1.5 M activating agent concentration, 105°C activation temperature, and 3.5 h activation time. In addition, the effects of adsorption parameters (viz., biosorbent dosage, temperature, initial concentration of Cr (VI), and contact time) were investigated. The maximum removal efficiency was attained at 2 g of biosorbent dosage, 4 h contact, 75 mg/L of initial Cr (VI) concentration, and 25°C sorption temperature. In addition, isotherm, kinetic, and thermodynamic studies for Cr (VI) biosorption were studied. The experimental adsorption data were well fitted with the Langmuir isotherm and pseudo-second-order kinetic model with higher correlation coefficient in both untreated and chemically modified Teff straw biosorbent. The investigated thermodynamic parameters ([Formula: see text], [Formula: see text], and [Formula: see text]) confirmed that Cr (VI) metal ions’ adsorption process onto Teff straw biosorbent was spontaneous and endothermic.

A Novel Biosorbent Functionalized Pillar[5]Arene: Synthesis, Characterization and Effective Biosorption of Cr(Vi)

A Novel Biosorbent Functionalized Pillar[5]Arene: Synthesis, Characterization and Effective Biosorption of Cr(Vi)

Sustainable removal of Cr(VI) from wastewater by Peltophorum pterocarpum leaf powder

Heavy metals discharged from various industrial activities instigate a significant risk to health risk and the environmental hazards. Numerous methods are available (namely electro-dialysis, ion exchange, membrane filtration, ultrafiltration and reverse osmosis) for removing heavy metals from industrial effluent. Chromium mainly hexavalent chromium i.e. Cr(VI) is considered to be one of the most toxic heavy metals amongst the list. The present work emphasizes on biosorption of Cr(VI) towards efficient removal. The current work highlights on optimization of process variable, which is influencing the removal through biosorption using Peltophorum pterocarpum leaf powder. The experimental design of Box-Behnken was applied to determine the optimum parametric conditions. Characterization of Peltophorum pterocarpum leaf powder (PPL) was carried out through FTIR and SEM analysis. The highest removal percentage was attained 90.94 through biosorption at pH- 4.15, initial concentration of 39.81 mg L−1 and biosorbent dosage of 0.3 g. The experimental sorption study obeyed the Langmuir isotherm and pseudo second-order kinetic models. Desorption studies were performed with 0.1 N NaOH solution for the regeneration of biosorbent. The entire experimental results concluded that Peltophorum pterocarpum leaf (PPL) powder could be a potential biosorbent for removal of hexavalent chromium from industrial wastewater.

Kinetic process of the biosorption of Cu(II), Ni(II) and Cr(VI) by waste Pichia pastoris cells

ABSTRACT Waste biomass of Pichia pastoris (P.pastoris) cells from the fermentation industry is an environmentally friendly biosorption material. The present study aimed to explore the biosorption behaviour of waste P.pastoris cells for Cu(II), Ni(II) and Cr(VI) in aqueous solution conditions. The results showed that the adsorption kinetics of three kinds of metals were well-fitted with lineared Elovich, pseudo-second-order kinetics models, non-linear kinetics and adsorption isotherms. The effective biosorption rates for Cu(II), Ni(II) and Cr(VI) removal were 71.3%, 59.7% and 16.25% respectively. The maximum Cu(II) adsorption capacity of waste P.pastoris was 40 mg/g at pH = 4 and 225 mg/L of solute concentration for 0.4 g biomass, better than that of the living yeasts. The pattern of Fourier transform infrared (FTIR) indicated that functional groups such as –NH, –OH, Si–O, P–O–C were involved in Cu(II) adsorption process. The analysis of SEM-EDS, XRD and TEM-EDS can be concluded that Cu(II) occupied Ca(II) binding sites by ion exchange mechanism to remove flocculation, and Cu(II) adsorbed onto the diatomite containing in the industrial waste P.pastoris. Thus the adsorption mechanism of the industrial waste P.pastoris was proposed taking Cu(II) as the example. And consecutive biosorption/desorption cycles were used for the evaluation of the regeneration efficiency, suggesting the good regeneration and reusability of waste P.pastoris.

Valorization of Biomass Residues by Biosorption of Microelements in a Closed-Loop Cycle

The concept of the research data presented assumes the valorization of goldenrod residues from supercritical CO2 extraction following the circular economy principles. The biomass was enriched with microelements (Cr, Zn, Cu) by biosorption from single and multielemental solutions in batch and packed bed reactors. Modeling of biosorption equilibrium supported by instrumental analysis (SEM and FTIR) of material properties was employed to explain the metal ions binding mechanism. The preferential biosorption of Cr(III) over the divalent ions, allows the possibility of valorization of goldenrod residue in a garden-scale biosorption tank acting as a fixed-bed reactor working in an open circulation run and fed with microelements diluted in rainwater. The use of fertigation solution in optimal doses of micronutrients did not show any phytotoxic effect. Using the post-sorptive solution as a source of micronutrients for plants showed significant effects on growth parameters (increased chlorophyll content by 54%) compared to groups fertilized with commercial formulation (13% higher sprout mass). Additionally, fertigation with the post-sorption solution leads to the biofortification of cucumber sprouts. The recycling process results in two products: enriched biomass as a potential feed additive (with Cr(III), Cu(II), and Zn(II)) and a post-sorption solution (with Zn(II) and Cu(II) only) used in the fertigation of plants.Graphical

Sherry wine industry by-product as potential biosorbent for the removal of Cr(VI) from aqueous medium

A low-cost biosorbent obtained from the Palomino Fino grape seed, a Sherry wine industry by-product, has been proposed as a way of valorising this material. The biomass was characterised obtaining values of 0.68 ± 0.05 g mL−1 for bulk density, 1.02 ± 0.09 g mL−1 for apparent density and 33.3% for porosity. The pHpzc was 5.2 and the surface negative charge value was 2.4 ± 0.2 mmol g−1. The analysis of surface morphology showed differences due to the sorption. The results showed a promising potential for chromium(VI) removal from aqueous solutions. The studies were carried out in batch scale and a 23 factorial design was applied for the optimisation of the process. A percentage of 91.7 ± 0.6% was achieved for the biosorption of Cr(VI) under optimal conditions using pH 5.5, 15 g/L of biosorbent and 8 h of contact time. The biosorption capacity showed a remarkable linearity from 0 to 2 mmol L−1 Cr(VI) and a precision of 0.64% for the removal of 1 mmol L−1 of metal. Langmuir, Freundlich and Temkin isotherm equations and the parameters of six kinetic models were used in the equilibrium modelling and identifying the mechanism of the biosorption. The combination of physical and chemical sorption mechanisms was proposed for the chromium removal with a high maximum sorption capacity (qmax = 208.3 mg g−1). Thermodynamic parameters indicated the spontaneous and endothermic nature of the chromium removal. The successful biosorption was based on the special grape seed components with a relevant content in antioxidant and lignocellulosic compounds.

Sustainable Chromium Recovery From Wastewater Using Mango and Jackfruit Seed Kernel Bio-Adsorbents.

Wastewater is a rich source of valuable chemicals of industrial importance. However, their economic recovery is crucial for sustainability. The objective of the present work is to recover hexavalent chromium (Cr VI) as a value-added transition metal from wastewater cost-effectively; the biosorbent derived from seed kernels of mango (M) and jackfruit (JF) were applied for removing the metal from simulated wastewater. The functional groups of the biomass were analysed with the help of Fourier transform infrared (FTIR) spectroscopy, micrographs were generated using a scanning electron microscope, and crystallinity was determined by an x-ray diffractometer (XRD). The concentration of Cr VI in wastewater was analysed by an inductively coupled plasma optical emission spectrometer (ICP-OES). Process parameters (pH, dose, contact time, temperature, and initial concentration) were optimized for efficient Cr VI adsorption using a response surface methodology-based Box–Behnken design (BBD) employing Design-software 6.0.8. The batch experiment at room temperature at pH 4.8 and Cr VI removal ∼94% (M) and ∼92% (JF) was achieved by using a 60-mg dose and an initial Cr (VI) concentration of 2 ppm in 120 min. The equilibrium Cr binding on the biosorbent was well explained using Freundlich isotherm (R2 = 0.97), which indicated the indirect interactions between Cr (VI) and the biosorbent. Biosorption of Cr (VI) followed the pseudo-order and intra-particle diffusion models. The maximum adsorption capacity of the M and JF bio-adsorbent is 517.24 and 207.6 g/mg, respectively. These efficient, cost-effective, and eco-friendly biosorbents could be potentially applied for removing toxic Cr (VI) from polluted water.

Synthesis of activated carbon from Borassus flabellifer empty fruit bunch waste and their application in chromium (VI) removal

ABSTRACT The present study emphasises that the synthesis of activated carbon (AC) from Borassus flabellifer empty fruit bunch waste (BFEFBW) and enhances the biosorption of chromium (Cr(VI)). The biosorption process was improved with four parameters: BFEFBWAC concentration, Cr(VI) dose, pH, and sorption time route utilising response surface methodology-Box-Behnken design (RSM-BBD). Fourier-transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FESEM), and X-ray diffraction (XRD) were used to characterise the BFEFBWAC before, and after-sorption of Cr(VI). The AC exhibits a porous structure with a variety of functional groups, according to the characterisation data. The ANOVA test was used to examine the experimental findings, which revealed that the regression model was acceptable. The maximum biosorption of Cr(VI) (89.35%) was achieved to be a BFEFBWAC of 8.0 g/L, Cr(VI) dose of 20 mg/L, pH 5.0, and a contact time of 120 min. The reusability of BFEFBWAC for Cr(VI) was examined for up to five cycles. It appears that BFEFBW-based AC has a substantial role in improving Cr(VI) removal from water.

Characterization of multi-metal-resistant Serratia sp. GP01 for treatment of effluent from fertilizer industries.

The effluent generated from fertilizer plants in Paradeep in the coast of the Bay of Bengal is the major pollutant causing health hazard in the vicinity of the area with respect to plants, animals and microbes. Samples of effluent were found to contain heavy metals (mg L-1): Cr (100), Ni (36.975), Mn (68.673), Pb (20.133), Cu (74.44), Zn (176.716), Hg (5.358) and As (24.287) as analyzed by XRF. Indigenous bacterial strains were screened for chromate and multi-metal resistance to remediate the toxic pollutants. The isolated strain G1 was identified as Serratia sp. through 16S-rDNA sequence homology. The potent strain Serratia sp. GP01 treated with 100mg L-1 of K2Cr2O7 has shown the efficacy of reducing 69.05mg L-1 of Cr over 48h of incubation. Further, presence of chromate reductase gene (ChR) in Serratia sp. confirmed the enzymatic reduction of Cr(VI). SEM-EDX and SEM mapping analysis revealed substantial biosorption of Cr and other heavy metals present in effluent by Serratia sp. GP01. Antioxidant enzymes such as catalase (72.15 U mL-1), SOD (57.14 U mL-1) and peroxidase (62.49 U mL-1) were found to be higher as compared to the control condition. FTIR study also revealed the role of N-H, O-H, C = C, C-H, C-O, C-N, and C = O functional groups of the cell surface of Serratia sp. treated with K2Cr2O7 and effluent from the fertilizer industry. Isolated strain Serratia sp. could be used for the detoxification of Cr(VI) and other heavy metals in fertilizer plant effluent.

Modelling and optimization of hexavalent chromium removal from aqueous solution by adsorption on low-cost agricultural waste biomass using response surface methodological approach.

In this study, a response surface methodology (RSM) approach using central composite design (CCD) was investigated to develop a mathematical model and to optimize the effects of pH, adsorbent amount and temperature related to the hexavalent chromium removal by biosorption on peanut shells (PSh). The highest removal percentage of 30.28% was found by the predicted model under the optimum conditions (pH of 2.11, 0.73 g of PSh and 37.2 °C) for a 100 mg/L initial Cr(VI) concentration, which was very near to the experimental value (29.92%). The PSh was characterized by SEM, EDX, FTIR, BET, XRD analyses. Moreover, a Langmuir isotherm fitted well (R2 = 0.992) with the experimental data, and the maximum adsorption capacity was discovered to be 2.48 and 3.49 mg/g respectively at 25 and 45 °C. Kinetic data were well foreseen by pseudo second order. Thermodynamic study depicted that biosorption of Cr(VI) onto PSh was spontaneous and endothermic. Regeneration of the PSh using NaOH showed a loss <5% in the Cr(VI) removal efficiency up to three recycle runs. In summary, the Cr(VI) removal onto economic, sensitive and selective biosorbent (PSh) was optimized using CCD to study biosorption behaviors.

Natural community of macroalgae from chromium-contaminated site for effective remediation of Cr(VI)-containing leachates

The natural macroalgal community, which developed in the unique and extremely Cr(VI)-polluted aquatic reservoir situated near a historical chromium-waste landfill, was studied in order to recognize the main mechanisms of Cr(VI) detoxification by the algal species. The conducted taxonomic analysis revealed mixed composition of the filamentous forms of algae and showed that three species of Tribonema, namely T. vulgare, T. microchloron and T. viride, which have not been studied before with regard to the mechanisms of Cr(VI) removal, are likely responsible for the effective bioremediation of this highly Cr(VI)-polluted habitat. The studied algal community, with the ability to grow in extremely high concentrations of Cr(VI), i.e. up to ca. 6150 times the upper limit for surface water, exhibited hyperaccumulative properties for chromium (max 16230 mg/kg dry weight) under the given environmental conditions. We found that the main mechanism of Cr(VI) detoxification was reduction followed by Cr(III) biosorption – feasibly by ion exchange and complexation mechanisms – and that the excellent efficiency of chromium reduction under the given, unfavorable weakly alkaline conditions indicates the biological origin of this process. It was concluded that the examined reservoir inhabited by the algal community can be used, after some modifications, as a simple cost-effective “bioreactor” allowing the reduction of chromium concentration to the desired level. Moreover, the conducted studies are also essential to obtain in-depth knowledge and should also be helpful in the relevance of the community for its further application as a potential biosorbent of Cr(VI) on a global scale.

An extensive review on chromium (vi) removal using natural and agricultural wastes materials as alternative biosorbents.

Several conventional techniques for heavy metals decontamination for instance ion exchange, evaporation, precipitation and electroplating have been utilized in preceding years. Though these techniques have some drawbacks, adsorption using low-cost biosorbents is environmentally friendly. In this study, the potential of several natural and agricultural wastes as economical biosorbents for the reduction of Cr(VI) ions from polluted water has been reviewed. The application of adsorption models, as well as the impact of adsorption factors on heavy metals eradication, has been considered in this review. The study revealed that efficient reduction of Cr(VI) from water and wastewaters is highly dependent on the pH of the solution, shaking time, adsorbent type, initial concentration and temperature. The review of the relevant literature indicates that the maximum removal efficiency of Cr(VI) using the various low-cost adsorbents ranged from 50.0-100.0% with optimum pH and contact time ranging from 2.0-6.0 and 30.0-180.0min, respectively at room temperature (25.0 °C). Furthermore, considering all the studies reviewed, the pseudo-second-kinetics and Langmuir isotherm are the dominant models that best described the Cr(VI) equilibrium data. The thermodynamic parameters suggested that the biosorption of Cr(VI) on the biosorbents was spontaneous, realistic and endothermic at the temperature range of 30.0-45.0 °C. It is found that the natural and agricultural wastes as cheap biosorbents are feasible replacements to commercial activated carbons for metal-contaminated water treatment. However, gaps have been identified to improve applicability, regeneration, reuse and safe discarding of the laden adsorbents, optimization and commercialization of suitable agricultural adsorbents.

Removal of Chromium(VI) from Contaminated Water Using Untreated Moringa Leaves as Biosorbent

Biosorption of chromium (Cr(VI)) is studied by using raw (chemically not modified) Moringa (Moringa Oleifera) leaf powder without any pretreatment. Cr(VI) is one of the potentially harmful heavy metals found in industrial wastewater. In the Moringa leaf powder, the presence of a significant amount of organic acids form the source for the biosorption of Cr(VI). The concentration of Cr(VI) in the feed solution is varied and different dosages of the proposed biosorbent are used to study its efficiency in the removal of Cr(VI). The concentration of Cr(VI) is varied from 1 ppm to 20 ppm while the amount of biosorbent is varied from 0.5 g to 2.5 g. The equilibrium time for adsorption of Cr(VI) is observed to vary between half an hour and 90 min. The metal removal efficiency varied from 30% to 90% which is a significant achievement compared to other conventional methods which are either energy-intensive or not cost effective. The experimental results are modeled using Langmuir, Freundlich and Redlich–Peterson isotherms. The metal removal efficiency is attributed to the chelating effect of carboxylate and hydroxyl groups present in the moringa leaves and is confirmed from the FTIR analysis. Further molecular docking simulations are performed to confirm the binding of the metal to the speculated sites within the different acids present in the moringa leaves. Untreated green moringa leaf powder used as a biosorbent in this study leads to a sustainable and cheaper option for treating wastewater containing Cr(VI).

Optimization of Hexavalent Chromium Biosorption by Shewanella putrefaciens Using the Box-Behnken Design

Cr(VI) is a ubiquitous pollutant that poses a serious threat to human health. Recently, the use of microorganisms to adsorb heavy metals has attracted research attention. However, there are few studies on the biosorption of Cr(VI) by Shewanella putrefaciens, which is a metal-reducing bacterium. In this paper, single-factor experiments were designed to investigate the effect of hexavalent chromium by Shewanella putrefaciens, and response surface methodology (RSM) based on the Box-Behnken design (BBD) was performed to study the Cr(VI) biosorption behavior of Shewanella putrefaciens. The coefficient of determination (R2 = 0.811 for Cr(VI)) and probability value (P < 0.05) demonstrated significance for the obtained regression model. The results showed that the model was suitable for experimental data, and the maximum Cr(VI) removal efficiency by Shewanella putrefaciens was 85.68% under the optimum conditions of a contact time of 16.57 h, pH value of 8, and biomass dosage of 0.42 g/L, which were verified by additional experiments. ANOVA and 3D response graph analysis showed that the variables with significant influences were pH and temperature. In addition, scanning electron microscopy (SEM) results demonstrated that after biosorption of Cr(VI) by Shewanella putrefaciens, granular complexes attached to rough cell surfaces were observed. Furthermore, Fourier transform infrared spectroscopy (FT-IR) analysis showed that the distribution of Cr(VI) on the cell surface was related to the carboxyl, ether, amide, hydroxyl, and phosphoric acid groups of Shewanella putrefaciens. This study is useful to explore the process and mechanism of heavy metal adsorption by Shewanella putrefaciens and provide new ideas for the microbial remediation of metal pollution in water.

Insight into Cr(VI) biosorption onto algal-bacterial granular sludge: Cr(VI) bioreduction and its intracellular accumulation in addition to the effects of environmental factors

Hexavalent chromium (Cr(VI)) is one of the typical heavy metals that pose a great threat to the environment. As a novel biotechnology, algal-bacterial aerobic granular sludge (AGS) possesses the merits of both bacterial AGS and algae. This study firstly evaluated Cr(VI) removal via biosorption by algal-bacterial AGS under different operation conditions and then some environmental factors. Results show that the highest Cr(VI) reduction (99.3%) and total Cr removal (89.1%) were achieved within 6 h at pH 2 and 6, respectively. The coexisting oxyanions exhibited slight effects, while both tested natural organic matters (humic acid and tannic acid) and carbon sources promoted Cr(VI) reduction at some appropriate concentrations. The coexistence of metal cations favored Cr(VI) reduction, achieving the highest enhancement of 8.1% by Cu2+ at 5 mg/L, while the total Cr removal was suppressed to some extent. Salinity > 5 g/L severely inhibited both Cr(VI) reduction and total Cr removal. Moreover, the loaded Cr in algal-bacterial AGS was found to be almost in the form of Cr(III), with 66.8% being contributed by intracellular accumulation. This work suggests that Cr(VI) reduction and intracellular accumulation are the main mechanisms involved in Cr(IV) biosorption onto algal-bacterial AGS.

Employing waste to manage waste: Utilizing waste biomaterials for the elimination of hazardous contaminant [Cr(VI)] from aqueous matrices

Pollution caused due to discharge of toxic and hazardous chemical contaminants from industrial processes is an issue of major environmental concern. Hexavalent chromium [Cr(VI)] is one such known toxic heavy metal contaminant emanated largely from various industrial processes. Since physical-chemical treatment techniques are beset with several problems, there is an increased attention on the use of waste biomaterials/biomass as sorbents for the elimination of heavy metals from aqueous matrices. The main purpose of this study was to evaluate the effectiveness of some low-cost waste biomaterials such as fruit wastes, agricultural and industrial waste/byproducts, waste parts of photosynthetic plants, aquatic plants and fungal biomass collected from different sources for the biosorption of Cr(VI) from aqueous matrices. Amid the tested biomaterials, wood apple shell (WAS) biomass (Limonia acidissima) was found to be highly efficient biosorbent for Cr(VI) sorption. In majority of biomass, it was observed that biosorption of Cr(VI) took place at acidic pH with optimum pH ranging from 2.0 to 5.0. Loading capacity of WAS biomass (29.37 mg/g) was higher than that of conventional adsorbent activated charcoal (26.56 mg/g), which was used as control. Cr(VI) treated biomass (WAS) was characterized using instrumental techniques such as Scanned Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) confirmed the adsorption of Cr(VI). Boehm titration and FTIR studies were conducted to ascertain the presence of functional groups responsible for Cr(VI) sorption by WAS biomass. The WAS biomass removed Cr(VI) from industrial wastewater with an efficiency of >99.9% thus complying with the statutory limits. Considering the economical aspect, the selected biomass can be viewed as a potential candidate for the elimination of toxic contaminant from wastewater.