Studies on enhancement of Cr(VI) biosorption by chemically modified biomass of Rhizopus nigricans

Utilization of Waste Biomaterial as an Efficient and Eco-Friendly Adsorbent for Solid-Phase Extraction of Pantoprazole Contaminants in Wastewater

The objective of this analysis is to establish the potential of biodegradable agro-industrial waste materials as biosorbents in the solid-phase extraction (SPE) technique for sample preparation. In this regard, waste coffee husk (CH) powder was collected, washed, treated chemically, characterized, and applied as an SPE adsorbent to extract pantoprazole from the wastewater samples. Sample detection was accomplished using the UPLC-MS/MS system. The positive mode of electrospray ionization was exploited for the ionization of the sample, and quantification of the target analyte was performed by the multiple reaction monitoring modes. The precursor to product ion transition of 384.02→1380.05 and 384.02→200.05 was used as qualifiers and quantifiers, respectively. Optimization of the particle size, adsorbent dose, and contact time were evaluated to select the best combination of features. The efficiency and regeneration capability of the CH were compared with respect to a commercially available silica-based C18 SPE adsorbent, and it was found that CH possessed comparable (~50%) extraction, as well as regeneration capacity (~95%). The developed biosorbent was applied in a wastewater sample spiked with the target analyte and recovery studies were performed, which found a range of 93.0 to 102.0% with a %RSD of 3.72 to 12.7%. Thus, CH can be exploited as a ‘greener’ replacement for the commercially available adsorbents for the extraction/retention of active pharmaceutical ingredients present in water/wastewater samples.

Extracellular proteins of Desulfovibrio vulgaris as adsorbents and redox shuttles promote biomineralization of antimony

Biomineralization is the key process governing the biogeochemical cycling of multivalent metals in the environment. Although some sulfate-reducing bacteria (SRB) are recently recognized to respire metal ions, the role of their extracellular proteins in the immobilization and redox transformation of antimony (Sb) remains elusive. Here, a model strain Desulfovibrio vulgaris Hildenborough (DvH) was used to study microbial extracellular proteins of functions and possible mechanisms in Sb(V) biomineralization. We found that the functional groups (N-H, CO, O-CO, NH₂-R and RCOH/RCNH₂) of extracellular proteins could adsorb and fix Sb(V) through electrostatic attraction and chelation. DvH could rapidly reduce Sb(V) adsorbed on the cell surface and form amorphous nanometer-sized stibnite and/or antimony trioxide, respectively with sulfur and oxygen. Proteomic analysis indicated that some extracellular proteins involved in electron transfer increased significantly (p < 0.05) at 1.8 mM Sb(V). The upregulated flavoproteins could serve as a redox shuttle to transfer electrons from c-type cytochrome networks to reduce Sb(V). Also, the upregulated extracellular proteins involved in sulfur reduction, amino acid transport and protein synthesis processes, and the downregulated flagellar proteins would contribute to a better adaption under 1.8 mM Sb(V). This study advances our understanding of how microbial extracellular proteins promote Sb biomineralization in DvH.

Biosorption of Remazol Brilliant Blue R dye onto chemically modified and unmodified Yarrowia lipolytica biomass

Remazol Brilliant Blue R (RBBR) is a widely used carcinogenic and toxic dye. This study focused on RBBR dye removal using chemically modified and unmodified Yarrowia lipolytica biomass. RBBR dye biosorption studies were carried out as a function of pH, initial dye concentration, biosorbent dose, contact time, and temperature. The pH of the aqueous solution strongly influenced the biosorption percent of RBBR dye. The highest dye biosorption capacity yield was obtained at pH 2-3 range. It has been found that the adsorption capacity is quite low at higher pH values. No differences were found between chemically modified and unmodified biomass in terms of RBBR dye biosorption capacity. In the first 15 min, almost 50% RBBR dye was removed from the solution and reached equilibrium within180 min at pH 2. Biosorption isotherm obeyed Langmuir isotherm model and pseudo-second-order kinetic model.

Clean approach for chromium removal in aqueous environments and role of nanomaterials in bioremediation: Present research and future perspective

Chromium is an insidious ecological pollutant that is of huge value for its toxicity. The existing ecological objective to lower the heights of toxic materials in marine systems and to stimulate the existing water to recycle after suitable treatment of wastewater. Chromium is a hazard element that appears in discharges of numerous industries that must be diminished to accomplish the goals. Nearly all of the findings described in the literature related to the usage of various materials such as fungal, algal, bacterial biomass, and nanomaterials for chromium adsorption. The current work evaluates the findings of research commenced in the preceding on the use of a variety of adsorbents to decrease chromium concentrations in contaminated waters. This review article focuses on the issue of chromium contamination, its chemistry, causes, consequences, biological agent remediation techniques, and the detailed process of chromium detoxification in microbial cells. It also lists a description of the in situ and ex situ chromium bioremediation methods used. This can help design more effective Cr(VI) removal methods, thus bridging the difference between laboratory discoveries and industrial chromium remediation applications.

Removal of Toxic Heavy Metals from Contaminated Aqueous Solutions Using Seaweeds: A Review

Heavy metal contamination affects lives with concomitant environmental pollution, and seaweed has emerged as a remedy with the ability to save the ecosystem, due to its eco-friendliness, affordability, availability, and effective metal ion removal rate. Heavy metals are intrinsic toxicants that are known to induce damage to multiple organs, especially when subjected to excess exposure. With respect to these growing concerns, this review presents the preferred sorption material among the many natural sorption materials. The use of seaweeds to treat contaminated solutions has demonstrated outstanding results when compared to other materials. The sorption of metal ions using dead seaweed biomass offers a comparative advantage over other natural sorption materials. This article summarizes the impact of heavy metals on the environment, and why dead seaweed biomass is regarded as the leading remediation material among the available materials. This article also showcases the biosorption mechanism of dead seaweed biomass and its effectiveness as a useful, cheap, and affordable bioremediation material.

Insight into biosorption of heavy metals by extracellular polymer substances and the improvement of the efficacy: a review

Heavy metals are continuously released into aquatic environments in which they accumulate. This phenomenon endangers public health because heavy metals accumulate along the food chain. However, conventional remediation methods are inefficient, expensive and yield toxic intermediate products, which adversely affect the environment. The discovery of green bio-adsorbents such as microbial extracellular polymer substance (EPS) has quickly attracted considerable worldwide attention because of their low cost, high removal efficiency of heavy metals and industrial availability. Hence, this review considers the sources, hazards and treatment methods of heavy metals pollution, particularly the biosorption mechanism of EPS to heavy metals and the influencing factors of the bio-adsorption process, which are significant in the efficient removal of heavy metals-containing wastewater treatment. This review also focuses on strengthening the process of EPS adsorption of heavy metals, which can further contribute to heavy metals removal. Finally, it has been proposed that improving the yield, stability, selectivity and recoverability of EPS is the key direction of further research.

Facile synthesis and characterization of polypyrrole - iron oxide - seaweed (PPy-Fe3O4-SW) nanocomposite and its exploration for adsorptive removal of Pb(II) from heavy metal bearing water

Lead is a widely used heavy metal which is highly toxic to kidney, nervous system and reproductive system. A special featured polypyrrole based adsorbent, with admirable salinity confrontation, environmental stability and reusability, was engaged to remove lead ions from aqueous solution. The advantages of using polypyrrole based adsorbent for heavy metal removal are: ease of synthesis, biocompatibility and high metal selectivity. In this study, polypyrrole - iron oxide - seaweed nanocomposite was proposed to remove lead ions from aqueous solution. A new method was adopted for the synthesis of polypyrrole - iron oxide - seaweed nanocomposite. The nanocomposite was prepared within a short time using ultra-assisted polymerization technique. The synthesized nanocomposite adsorbent was characterized using FTIR, SEM, TEM, EDS, XRD, XPS and zeta potential analysis. The adsorption capability of polypyrrole - iron oxide - seaweed nanocomposite towards lead was explored. The influence of pH, contact time, adsorbent dosage, metal ion concentration and recyclability were investigated. The optimum condition of these parameters was found to be: pH- 5, temperature - 40 °C, initial concentration - 100 mg/L and contact time - 20 min and the results showed that the hybrid composite adsorbed 97.25% Pb (II). Different isotherms such as Langmuir, Freundlich, Temkin and D-R models were also studied for the adsorption of Pb ions. The kinetics of the adsorption process was examined by I order, II order and intra particle diffusion kinetic models. The mechanism of lead adsorption onto the nanocomposite was also explored.

Optimization of chromium(VI) removal by indigenous microalga (Chlamydomonas sp.)-based biosorbent using response surface methodology

Phycoremediation of heavy metals has garnered considerable recent research interest. In this study, an indigenous microalga (Chlamydomonas sp.)-based biosorbent was employed for biosorption of Cr(VI) dissolved solids (Cr(VI)-DS), optimized using response surface methodology (RSM). The effects of microalga concentration, pH, and contact time were studied with 250 mg Cr(VI)-DS L^-1 . The biosorption of Cr(VI)-DS was higher at acidic pH (94.17% at pH 4) than at alkaline conditions (68.53% at pH 10). The interaction of pH and microalga concentration exerted significant (p < 0.05) influence on the biosorption. Under the optimized parameters of 1.5 g microalga L^-1 , pH 4, and contact time of 30 min, a predicted biosorption of 91.31% and biosorption capacity of 152 mg Cr(VI)-DS g^-1 biomass were documented. FTIR analysis attested the electronegative surface functional groups of the microalgae biomass, bracketed together with its high biosorption potency. The study evinced the potential of the indigenous microalga for remediation of hexavalent chromium. PRACTITIONER POINTS: Indigenous Ethiopian microalga (Chlamydomonas sp.) exhibited 94% Cr(VI) abatement with biosorption capacity of 152 mg Cr(VI) g^-1 . FTIR analysis of the biosorbent divulged the presence of electronegative functional groups (amino, carboxyl, hydroxyl, and carbonyl groups). Higher biosorption of Cr(VI)-DS under acidic pH (94.17% at pH 4) than alkaline pH (68.53% at pH 10). Significant (p < 0.05) interaction effect of pH and biomass concentration on the biosorption, evinced in RSM optimization 91% Cr(VI) removal achieved under optimal conditions of 1.5 g biosorbent L^-1 , 30 min of contact time, and pH 4.

Removal of lead ions in an aqueous solution by living and modified Aspergillus niger

An indigenous lead-tolerant fungal strain was isolated from lead-contaminated soil and identified as Aspergillus niger, via 18S rRNA gene sequencing. We determined the adsorption and accumulation of Pb(II) by living A. niger and the adsorption of Pb(II) via modified A. niger. This strain resisted and removed 96.21%-100% Pb(II) ranging from 2 to 8 mmol/L Pb(II). Pb-containing particles were observed outside of the cell, and lead was detected inside the cell under scanning electron microscopy and transmission electron microscopy. The process of measuring the adsorption ability of modified fungal biomass, freeze-dried, high-temperature, and alkali-treated fungal samples was analyzed; they adsorbed 25.02%, 8.76%, and 15.05% Pb(II) under 8 mmol/L Pb(II) in 43, 10, and 10 hr, respectively. These three types of modified A. niger fit the pseudo-second-order model equation well. PRACTITIONER POINTS: Isolation and identification of effective Pb(II) removal strain from the soil around Dexing lead-zinc mine. The ability of living and modified Aspergillus niger to remove Pb(II) in an aqueous environment was evaluated. Lead distributions inside and outside the cell were analyzed by SEM and TEM. Kinetic models for modified biomass adsorbing Pb(II) were made for describing adsorption process.

New insight into continuous recirculation-process for treating arsenate using bacterial biosorbent

In this study, a new recirculation column reactor system for arsenate removal using a polyethylenimine coated bacterial biosorbent was developed. Solution pH was the most important factor in process design and operation. In order to control and optimize solution pH favorable for arsenate removal, a pH control and recirculation system was added to a column reactor. The effects of recycle ratio, initial arsenate concentration, and flow rate on the arsenate removal performance of the developed process were examined. Thomas and Yoon-Nelson models were used to interpret the breakthrough curve of arsenate removal. The maximum arsenate adsorption amount of the new reactor was determined to be 50.86 mg/g by the Thomas model. Importantly, the new reactor showed unimpeded adsorption performance compared with that in the batch experiments. The desorption study also showed excellent reusability. The results indicated that the newly developed process could be a promising application prospect for removing arsenate.

Key role of pore size in Cr(VI) removal by the composites of 3-dimentional mesoporous silica nanospheres wrapped with polyaniline

A series of three-dimensional silica nanospheres with different pore sizes was synthesized in a biphasic oil-water system and their pore dimensions were adjusted by controlling the composition of the oil phase. The silica nanospheres were then wrapped with polyaniline, characterized, and the obtained silica nanosphere-polyaniline composites were used for the removal of Cr(VI). Polyaniline was generated by the polymerization of aniline. The mesoporous silica has sufficient dendritic pore channels and offers a large contact surface for the polymerization of aniline. Furthermore, the mesoporous silica nanospheres are beneficial for dispersing polyaniline and transferring aqueous Cr(VI). The silica nanosphere-polyaniline composite with the largest pore size (~15.4 nm) showed the best Cr(VI) removal performance. We also investigated the kinetic characteristics and the result could be fitted to the pseudo-second-order kinetic model. Moreover, we demonstrate that the composites maintain a high Cr(VI) removal efficiency compared to other anions (H₂PO₄^-, SO₄^2-, etc.), indicating their good prospect in practical wastewater treatment. Remarkably, the silica-polyaniline composites showed enhanced Cr(VI) removal efficiency under UV-irradiation. The effects of electrons and H⁺ on Cr(VI) reduction are also discussed based on the results of UV-vis and X-ray photoelectron spectroscopic studies and bath experiments (influence of pH on adsorption capacity). Mechanistic studies indicate that the Cr(VI) removal occurs in two stages-adsorption and reduction. The negatively charged aqueous Cr(VI) species first interact with the positively charged protonated amine groups via electrostatic attraction, and are then further reduced to less-toxic Cr(III) by the electrons and H⁺ donated by the amine groups on polyaniline.

Cr(VI) removal by Penicillium oxalicum SL2: Reduction with acidic metabolites and form transformation in the mycelium

Bioremediation of Cr(VI) contamination using microorganisms is a promising method for reducing its environmental risks. The objective of this study was to clarify Cr(VI) removal by Penicillium oxalicum SL2 in terms of indirect Cr(VI) reduction by metabolites, interaction sites, and form transformation of chromium. Strain SL2 could sequentially remove Cr(VI) in the bioreactor. Oxalic acid produced by the fungus contributed to Cr(VI) reduction. Scanning transmissiony X-ray microscop (STXM) analysis suggested strain SL2 could partly reduce Cr(VI) to Cr(III) in the cell. Amine, carboxyl, and phosphate groups were related to Cr(VI) removal. Chromium K-edge X-ray absorption near edge structure (XANES) analysis implied Cr(III)-Cys potentially acted as an intermediate for the formation of chromium oxalate complexes during the process of treatment. This study would support the application of strain SL2 in Cr(VI) bioremediation and expand knowledge on the interaction of chromium with fungus.

The improved methods of heavy metals removal by biosorbents: A review

For decades, a vast array of innovative biosorbents have been found out and used in the removal of heavy metals, including bacteria, algae and fungi, etc. Although extensive biological species have been tried as a biosorbent for heavy metals removal, for removal efficiency or economy efficiency limited, it has failed to make a substantial breakthrough in practical application. Thus, many improved methods based on biosorbents emerged. In this review, based on the literature and our research results, we highlight three types of novel methods for biosorbents removal of heavy metals: chemical modification of biosorbents; biomass and chemical materials combination; multiple biomass complex systems. We mainly focus on their configuration, biosorption performance, their creation method, regeneration/reuse, their application and development in the future. Through the comparative analysis of various methods, we think that intracellular autogenous nanomaterials may open up another window in biosorption of heavy metals area. At the same time, the combination of various treatment methods will be the development tendency of heavy metal pollution treatment in the future.

Fungal cell with artificial metal container for heavy metals biosorption: Equilibrium, kinetics study and mechanisms analysis

White-rot fungi show low-cost superiority as a promising biosorbent in heavy metal removal, but limited by its poor biosorption capacity. Herein, a novel biosorbent, functionalized Phanerochaete chrysosporium with intracellular mineral scaffold, was prepared for the biosorption of heavy metal ions. The functionalized fungi cells with intracellular mineral scaffold that serve as internal metal container exhibiting high biosorption efficiency for Pb(II) and Cd(II) ions. Adsorption isotherm models were employed to investigate the biosorption isotherm and determine the biosorption equilibrium. The Freundlich model shows better fit with the experimental data of both metal ions (R² = 0.9866 and 0.9897 for Pb(II) and Cd(II) respectively). Three kinetic models, pseudo-first-order, pseudo-second-order and intra-particle diffusion models, were used to determine the biosorption kinetics. The pseudo-second-order model shows the better fit with the experimental data, and we suggests the rate-limiting step of the biosorption could be a chemisorption step which involves sharing or exchanging of electrons between adsorbent and adsorbate. Intra-particle diffusion model study result shows the biosorption process could be divided into three steps: a fast surface adsorption stage, a slow transfer stage from external to internal, and a stage of andante reaching equilibrium. The biosorption mechanism was carefully analyzed by various characterization methods.

Novel biosorbents synthesized from fungal and bacterial biomass and their applications in the adsorption of volatile organic compounds

Adsorption is an efficient and low-cost technology used to purify volatile organic compounds (VOCs). In the current study, novel microbial adsorbents were synthesized using cells of lyophilized fungi (Ophiostoma stenoceras LLC) or bacteria (Pseudomonas veronii ZW) that were modified by aminomethylation. Based on the adsorption performance and structural characterization results, the modified fungal biosorbent was the best. Its maximum adsorption capacities for ethyl acetate, α-pinene, and n-hexane were 620, 454, and 374 mg·g^-1, respectively, which were much higher than those of other synthesized biosorbents. The specific surface area of the fungal biosorbent was 20 m²·g^-1, and most of the components were hydrocarbon compounds and polysaccharides. The VOC adsorption process on these synthesized biosorbents was in accordance with the Langmuir isothermal model and the pseudo-first-order kinetic model, thereby suggesting that physical adsorption was the dominant mechanism. The fungal biosorbent could be used for five consecutive VOC sorption-desorption cycles without any obvious decrease in adsorption capacity.

Cr(VI) adsorption from aqueous solution by fungal bioremediation based using Rhizopus sp

The highly toxic species of Chromium in its hexavalent state is an important hazard to the flora and fauna, causing a rupture in balance especially in aquatic environments. The removal of Cr(VI) ions from aqueous solutions using fungal biomass of Rhizopus sp. was investigated under batch experiments. The biomass was produced and treated with NaCl to compare pre-treated and untreated biosorbents capacity. Adsorption of Cr(VI) was investigated with a 2³ experimental design to determine the best operational parameters including pH [2.0-4.0], temperature [20-40 °C] and agitation [50-150 rpm]. Maximum Cr(VI) uptake (99%) indicated that pH 2.0 is the optimal for Cr(VI) removal. Linear and non-linear kinetic models were evaluated. The best fitting for linear kinetics was the pseudo-second order linear equation and the Elovich model in its non-linear form, suggesting chemisorption as the controlling step of adsorption. Results followed Langmuir isotherm equation, the q_m was 9.95 (mg·g^-1) for Rhizopus sp. + NaCl. Thermodynamic parameters were calculated using the adsorption equilibrium constant obtained from Langmuir isotherm and indicated that the adsorption process was spontaneous and endothermic. The surface characteristics of the biomass were analyzed by Fourier transform infrared (FTIR) spectra; the analysis showed the involvement of amino groups in the bonding with Cr(VI). SEM and EDX analysis confirmed the presence of Cr in the biomass after adsorption. The results of these experiments may be utilized for modeling, simulation, and scale-up processes in the future.

Chemical pretreatments of Trapa bispinosa's peel (TBP) biosorbent to enhance adsorption capacity for Pb(ll)

In this study, Trapa bispinosa's peel (TBP) biomass is exploited as an effective, low cost and new adsorbent to remove Pb(II) from aqueous solution. TBP is pretreated and modified with HNO3, HClO4 and H2O2 to enhance the Pb(II) removal and it is perceived that chemical modifications enhance the adsorption capacity of TBP. The adsorption behavior of Pb(II) is studied under different conditions, including pH (3-6), TBP dose (0.050.8 g), stirring speed (100-200 rpm), initial Pb(II) ion concentration (25-400 mg L-1) and contact time (0-1440 min). Kinetic study reveals sorption is fast in first 15 to 30 min achieving equilibrium in 60 min with qmax (mg g-1) are 77.09, 105.40 and 123.82 for NT-TBP, NA-TBP and HCA-TBP respectively. The Langmuir model successfully defines the sorption data having higher R2 and good agreement between theoretical and experimental uptake capacity of Pb(II). The kinetic study exhibits that the pseudo-second order rate equation is better portrayed sorption process. TBP modified with HClO4 shows the highest metal uptake in comparison to HNO3, H2O2 modified TBP and native TBP.

Phenol and Cr(VI) removal using materials derived from harmful algal bloom biomass: Characterization and performance assessment for a biosorbent, a porous carbon, and Fe/C composites

Lake Erie experiences annual harmful algal blooms (HAB), but generated HAB biomass may provide a waste-based precursor for environmental remediation materials. Three classes of materials (i.e., algal powder biosorbent, porous carbon, and iron/carbon (Fe/C) composite) are prepared from HAB biomass. Algal powder is nonporous with diverse functional groups. Porous carbon, prepared via one-pot carbonization and activation, has surface area up to 430 m²/g. Fe/Cs are prepared by cultivating HAB biomass in iron-rich media, followed by one-pot pyrolysis. Fe/Cs have over 6 wt% iron (Fe⁰ and Fe₃O₄) and nitrogen doping (up to 4 wt%). Materials were applied in phenol and Cr(VI) removal tests to identify preferred products for use in water treatment applications. In deionized water, porous carbon removes the most phenol (52 mg/g), followed by algal powder (38 mg/g) and Fe/C (33 mg/g). Micropore volume and functional groups improve phenol removal. Cr(VI) removal follows: Fe/C (43 mg/g) > porous carbon (28 mg/g) > algal powder (17 mg/g), with synergistic adsorption and reduction elevating Fe/C's performance. Cr(VI) and phenol removal studies were completed with variable pH, ionic strength, and water composition to highlight application potential. This work proposes HAB biomass reuse for pollution control, investigating interaction mechanisms between materials and contaminants.

Removal of Cr(VI) from synthetic wastewater by adsorption onto coffee ground and mixed waste tea

We attempted to recycle mixed waste tea and coffee ground as alternative low-cost adsorbents for Cr(VI) removal. The adsorption parameters optimized were: initial Cr(VI) concentration (10-30 mg L^-1), contact time (180 min), adsorbent dose (2.0 g L^-1), initial pH (2.0), temperature (30-50 °C), and agitation speed (250 rpm). Freundlich isotherm was found better fitted with a high correlation coefficient (R² = 0.97 for mixed waste tea and 0.92 for coffee ground) than to Langmuir model (R² = 0.89 for mixed waste tea and 0.86 for coffee ground) for the 10-250 mg L^-1 concentration range. Analysis of kinetic studies indicated that Cr(VI) adsorption by both adsorbents was consistent with the pseudo-second-order kinetic model with a good R² and Marquardt's present standard deviation (MPSD) values. Experimental data demonstrated a sorption capacity of 94.34 mg g^-1 of mixed waste tea and 87.72 mg g^-1 of coffee ground. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy dispersive X-ray spectroscopy (EDS) revealed the noticeable chromium accumulation on the adsorbent surfaces after adsorption. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) studies showed that carbon and oxygen functional groups on the surface of both adsorbents involved in Cr(VI) adsorption. The adsorbents could be reused four times. Large-scale operation using 100 L of packed-bed reactor showed the breakthrough time of adsorption for mixed waste tea of 30 min in 100 mg L^-1 Cr(VI) concentration. These results suggested that mixed waste tea and coffee ground be considered as alternative adsorbent for Cr(VI) removal.

Preparation of a novel nano-Fe3O4/triethanolamine/GO composites to enhance Pb2+/Cu2+ ions removal

In this paper, a magnetic nano-Fe₃O₄/triethanolamine/GO composite (TEA-GO-FE) was prepared by using graphene oxide (GO), triethanolamine (TEA), and ferric chloride. The result indicates that triethanolamine acted as an important role for the growing of Fe₃O₄ and adsorption ability of composite material. The synthesis mechanism of TEA-GO-FE was investigated through the medium of SEM-EDS, XRD, FT-IR, and TEM. The characterization results indicated Fe₃O₄ nanoparticles have been successfully loaded on the surface of graphene oxide and they were encapsulated by TEA and have excellent stability. According to the results of XRD, the general particle size of Fe₃O₄ on TEA-GO-FE was 27.5 nm. In order to understand the adsorption properties of TEA-GO-FE for Pb²⁺ and Cu²⁺, this article uses a static adsorption study method. The optimized adsorption conditions are as follows: pH = 5.0, temperature is 293.15 K, and the ion concentration is 100 mg/L. Under the optimized prerequisites, the adsorption capacities of Pb²⁺ and Cu²⁺ were 121.5 mg/g and 68.7 mg/g, separately. Through thermodynamic as well as kinetic studies, the adsorption process of Pb²⁺ and Cu²⁺ on TEA-GO-FE is a self-heating process.

Toxicological Assessment of Cross-Linked Beads of Chitosan-Alginate and Aspergillus australensis Biomass, with Efficiency as Biosorbent for Copper Removal

Sorbent materials of biological origin are considered as an alternative to the use of traditional methods in order to remove heavy metals. Interest in using these materials has increased over the past years due to their low cost and friendliness to the environment. The objective of this study was to synthesize and characterize cross-linked beads made of chitosan, alginate, and mycelium of a copper-tolerant strain of Aspergillus australensis. The acute toxicity of the biocomposite beads was assessed using brine shrimp Artemia salina nauplii and the phytotoxicity was determined using lettuce (Lactuca sativa) and chili pepper 'Anaheim' (Capsicum annuum) seeds. The biosorption capacity for copper removal in simulated wastewater was also evaluated. Results showed that the biosorbent obtained had a maximal adsorption of 26.1 mg of Cu²⁺ per g of biocomposite, and removal efficiency was around 79%. The toxicity of simulated residual water after treatment with the biocomposite showed low toxicity toward seeds, which was highly dependent on the residual copper concentration. The toxicity of the biocomposite beads to A. salina was considered medium depending on the amount of the biocomposite, which was attributed to low pH. Biocomposite shows promise as biosorbent for the removal process of heavy metals.

Bioremediation of hexavalent chromium by endophytic fungi; safe and improved production of Lactuca sativa L

One of the main problems of the industrialized world is the accumulation of chromium (Cr) in soil, which is a serious threat to the crops. Complete removal of Cr from the contaminated soils poses a great challenge. However, this issue can be minimised by using plant growth promoting microbes as a bioremediation tool. In the present study, healthy plants established near the University campus in Mardan were selected for the isolation of Cr resistant endophytes. From the designated plants, 114 species of endophytic fungi were isolated. Among the 114 isolated strains, 4 strains have induced resistance in L. sativa against Cr. The strains were identified as Aspergillus fumigatus, Rhizopus sp., Penicillium radicum and Fusarium proliferatum based on ITS region (18 S rDNA) homology. The isolates have removed Cr from soil and culture media as well as bio-transformed it from highly toxic hexavalent to least toxic trivalent form, thus helped the Cr stressed L. sativa to restore its normal growth. The Rhizopus Sp. CUC23 has mainly accrued Cr and detoxified intracellularly, whereas A. fumigatus ML43 and P. radicum PL17 has detoxified up to 95% of Cr extracellularly. From the results, it is concluded that the selected endophytic strains might be used as biofertilizer for healthy and safe crop production in Cr contaminated soils.

Wicherhamomyces anomalus biofilm supported on wood husk for chromium wastewater treatment

A Wickeramomyces anomalus biofilm supported on wood husk was used to remediate water bodies contaminated with chromium (Cr), in batch and open systems. The favorable adhesion ability of the chromium-resistant yeast strain on the wood husk was predicted by XDLVO theory and confirmed by environmental scanning electronic microscopy. The chromium decontamination was then optimized in a batch mode using a central composite design (CCD). Analysis of variance (ANOVA) showed a high coefficient of determination (R²) value of 0.93-0.91 for Cr(VI) and total Cr removal, respectively, ensuring a satisfactory fitting of the second-order regression model to the experimental data. In batch system, the concentration of biomass exhibited the minimal effect on the process. An acidic pH of 3.72 and 5.48, an initial chromium concentration of 10 and 16.91 mg/L and a support dose of 6.95 and 8.20 g/L were optimal for Cr(VI) and total Cr removal, respectively. The breakthrough curves were determined in open system for different initial chromium concentrations. The study of glucose concentration effect on the yeast extracellular polymeric substances (EPS) production showed that a medium exempt of glucose allowed maximal EPS production and minimal chromium removal efficiency, while 20 g/L glucose concentration of presented the optimal condition for chromium removal.

Recent advances on biosorption by aerobic granular sludge

Aerobic granular sludge is a form of microbial auto-aggregation, and a promising biotechnology for wastewater treatment. This review aims at providing the first comprehensive, systematic, and in-depth overview on the application of aerobic granules as biosorbents. The target pollutants encompass heavy metals (both cationic and oxyanionic), nuclides, dyes, and inorganic non-metal substances. Different granule types are discussed, i.e. intact and fragmented, compact and fluffy, original and modified, and the effects of granule surface modification are introduced. A detailed comparison is conducted on the characteristics of granular biomass, the conditions of the adsorption tests, and the resultant performance towards various sorbates. Analytical and mathematical tools typically employed are presented, and possible interactions between the pollutants and granules are theorized, leading to an analysis on the mechanisms of the adsorption processes. Original granules appear highly effective towards cationic metals, while surface modification by organic and inorganic agents can expand their applicability to other pollutants. Combined with their advantages of high mechanical strength, density, and settling speed, aerobic granules possess exceptional potential in real wastewater treatment as biosorbents. Possible future research, both fundamental and practical, is suggested to gain more insights into the mechanism of their function, and to advance their industrial application.

Cadmium Removal from Aqueous Solutions by Strain of Pantoea agglomerans UCP1320 Isolated from Laundry Effluent

Background:

Cadmium (Cd), which is a deadly heavy metal of work-related and environmental concern, has been recognized as a substance that is teratogenic and carcinogenic for humans. Therefore, the need to develop low-cost adsorbents to remove heavy metals from aqueous solution has greatly increased. Adsorbents such as Pantoea agglomerans biomass have been used.

Aims:

We investigated the biotechnological potential of Pantoea agglomerans for the biosorption of cadmium from aqueous solution.

Patients and Methods:

Pantoea agglomerans UCP1320 isolated from the effluent of a laundry industry was used to remove cadmium from aqueous solutions. Two approaches were compared using active or thermally inactivated biomass. Three different cadmium concentrations of 1, 10 and 100 ppm were used under constant stirring at temperatures of 25°C and 35°C as was pH of 3.0, 5.0 and 7.0. Variable incubation times of 1, 6, and 24h were also studied.

Results:

The results showed that the temperature did not influence the uptake of metal by living cells nor by inactive bacterial biomass. However, increasing the pH had a positive effect on removing intermediate concentrations of cadmium. Low concentrations of cadmium were completely removed by both live and inactive biomass.

Conclusion:

Pantoea agglomerans biomass was shown to have a promising performance for the biotechnological removal of cadmium which had been dissolved in aqueous solution.

Fast photoelectro-reduction of CrVI over MoS2@TiO2 nanotubes on Ti wire

A stable MoS₂ nanosheets@TiO₂ NTAs composite was prepared via a simple hydrothermal process. Few-layer MoS₂ nanosheets distributed on the TiO₂ nanotube top surface and the inner walls rather than filling in the tubes, allowing abundant tubular channels open to environment and benefiting for efficient mass transport. Photocatalytic (PE) and photoelectrocatalytic (PEC) performance of the composite were evaluated on Cr^VI reduction, with variable low molecule weight organic acids (LOAs) added as sacrificial electron donor to form a charge-transfer-complex (CTC) between LOAs and TiO₂/MoS₂, which is sensitive to the visible light illumination and could induce the photo-reduction of Cr^VI and photo-oxidation of LOAs. The overall trend of Cr^VI PEC rates are in the order as: L(+)-Tartaric acid>oxalic acid>citric acid>malic acid>amber acid, which is 103.9>62.5>31.2>21.6>2.5mg/Lmin^-1cm^-2, respectively. The improved catalytic performance and excellent stability of the composite can be attributed to the abundant active adsorption and reaction sites on MoS₂ nanosheets and the formation of a heterojunction between TiO₂ and MoS₂. Moreover, the appropriate application of LOAs and voltage also have a great contribution to the utilization of sunlight and efficient separation of photogenerated carriers.

Study of the adsorption and electroadsorption process of Cu (II) ions within thermally and chemically modified activated carbon

The aim of this work is to modify the porous texture and superficial groups of a commercial activated carbon through chemical and thermal treatment and subsequently study the kinetics of adsorption and electroadsorption of Cu (II) ion for these carbons. Samples of three activated carbons were used. These were a commercial activated carbon, commercial activated carbon modified thermically (C-N₂-900) and finally commercial activated carbon modified chemically C-SO₂-H₂S-200. The activated carbons were characterized chemically and texturally and the electrical conductivity of them determined. Different kinetic models were applied. The kinetics of the adsorption and electroadsorption process of the Cu (II) ion fits a pseudo second order model and the most likely mechanism takes place in two stages. A first step through transfer of the metal mass through the boundary layer of the adsorbent and distribution of the Cu (II) on the external surface of the activated carbon and a second step that represents intraparticle diffusion and joining of the Cu (II) with the active centres of the activated carbon. Finally, the kinetics of the adsorption process are faster than the kinetics of the electroadsorption but the percentage of the Cu (II) ion retained is much higher in the electroadsorption process.

Characterization and lead(II) ions removal of modified Punica granatum L. peels

The aim of the present study was to enhance the biosorption capacity of a waste biomass of Punica granatum L. peels (PGL) using various chemical modification agents. Among these agents, hexamethylenediamine (HMDA) indicated the best performance with regard to the improvement of lead(II) ions removal from aqueous solution. The characterization of HMDA-modified P. granatum L. peels (HMDA-PGL) was achieved by using elemental analysis, FT-IR, thermogravimetric (TG) analysis and zeta potential measurement techniques. Based on FT-IR study, the chemical modification of P. granatum L. peels take place with its carboxyl, carbonyl, hydroxyl, etc. groups and these groups are responsible for the biosorption of lead(II) ions onto modified biomass. Biosorption equilibrium and kinetic data fitted well the Langmuir isotherm and the pseudo-second-order kinetic models, respectively. The highest biosorption capacity obtained from Langmuir isotherm model was 371.36 mg g^-1. Biosorption process was spontaneous and endothermic in nature according to the thermodynamic results and it quickly reached the equilibrium within 60 minutes. The validity of kinetic models used in this study can be quantitatively tested by using a normalized standard deviation Δq(%).

Chemically modified surface functional groups of Alcaligenes sp. S-XJ-1 to enhance its demulsifying capability

Cell-surface functional groups (amino, carboxyl, hydroxyl, as well as phosphate) were chemically modified in various ways to enhance the demulsification capability of the demulsifying bacteria Alcaligenes sp. S-XJ-1. Results demonstrated that the demulsifying activity was significantly inhibited by amino enrichment with cetyl trimethyl ammonium bromide, amino methylation, hydroxyl acetylation, and phosphate esterification, but was gradually promoted by carboxyl blocking with increasing the extents of esterification. Compared with the raw biomass, an optimal esterification of carboxyl moieties enhanced the demulsification ratio by 26.5% and shortened the emulsion half-life from 24 to 8.8 h. The demulsification boost was found to be dominated by strengthened hydrophobicity (from 53° to 74°) and weakened electronegativity (from -34.6 to -4.3 mV at pH 7.0) of the cell surface, allowing the rapid dispersion and adsorption of cells onto the oil-water interface. The chemical modification of the functional groups on the biomass surface is a promising tool for the creation of a high-performance bacterial demulsifier.

Preparation of 4-vinylpyridine (4VP) resin and its adsorption performance for heavy metal ions

The study focused on the preparation of a chelating resin with pyridine ring as the functional group.

Contribution of surface functional groups and interface interaction to biosorption of strontium ions by Saccharomyces cerevisiae under culture conditions

Surface functional group contributions to biosorption of strontium ions bySaccharomyces cerevisiaeas well as interface interactions were elucidated.

Photo-mediated optimized synthesis of silver nanoparticles for the selective detection of Iron(III), antibacterial and antioxidant activity

The AgNPs synthesized by green method have shown great potential in several applications such as biosensing, biomedical, catalysis, electronic etc. The present study deals with the selective colorimetric detection of Fe³⁺ using photoinduced green synthesized AgNPs. For the synthesis purpose, an aqueous extract of Croton bonplandianum (AEC) was used as a reducing and stabilizing agent. The biosynthesis was confirmed by UV-visible spectroscopy where an SPR band at λ_max 436nm after 40s and 428nm after 30min corresponded to the existence of AgNPs. The optimum conditions for biosynthesis of AgNPs were 30min sunlight exposure time, 5.0% (v/v) AEC inoculum dose and 4mM AgNO₃ concentration. The stability of synthesized AgNPs was monitored up to 9months. The size and shape of AgNPs with average size 19.4nm were determined by Field Emission Scanning Electron Microscope (FE-SEM) and High-Resolution Transmission Electron Microscope (HR-TEM). The crystallinity was determined by High-Resolution X-ray Diffractometer (HR-XRD) and Selected Area Electron Diffraction (SAED) pattern. The chemical and elemental compositions were determined by Fourier Transformed Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDX) respectively. The Atomic Force Microscopy (AFM) images represented the lateral and 3D topological characteristics of AgNPs. The XPS analysis confirmed the presence of two individual peaks which attributed to the Ag 3d3/2 and Ag 3d5/2 binding energies corresponding to the presence of metallic silver. The biosynthesized AgNPs showed potent antibacterial activity against both gram-positive and gram-negative bacterial strains as well as antioxidant activity. On the basis of results and facts, a probable mechanism was also proposed to explore the possible route of AgNPs synthesis, colorimetric detection of Fe³⁺, antibacterial and antioxidant activity.

Sorption of zinc onto elemental selenium nanoparticles immobilized in Phanerochaete chrysosporium pellets

The use of a novel hybrid biosorbent, elemental selenium nanoparticles (nSe⁰) immobilized in pellets of Phanerochaete chrysosporium, to remove Zn from aqueous solutions was investigated. Fungal pellets containing nSe⁰ (nSe⁰-pellets) showed to be better biosorbents as they removed more Zn (88.1 ± 5.3 %) compared to Se-free fungal pellets (56.2 ± 2.8 %) at pH 4.5 and an initial Zn concentration of 10 mg L^-1. The enhanced sorption capacity of nSe⁰-pellets was attributed to a higher concentration of sorption sites resulting in a more negative surface charge density, as determined by analysis of the potentiometric titration data. Fourier transform infrared spectroscopy (FT-IR) analysis of fungal pellets prior to and after being loaded with Zn showed the functional groups, including hydroxyl and carboxyl groups, involved in the sorption process. The experimental data indicated that the sorption rate of the nSe⁰-pellets fitted well to the pseudo-second order kinetic model (R ²  = 0.99), and the sorption isotherm was best represented by the Sips model (Langmuir-Freundlich) with heterogeneous factor n = 1 (R ²  = 0.99), which is equivalent to the Langmuir model. Operational advantages of fungal pelleted reactors and the Zn removal efficiencies achieved by nSe⁰-pellets under mild acidic conditions make nSe⁰-pellet based bioreactors an efficient biosorption process.

Multiple heavy metal removal using an entomopathogenic fungi Beauveria bassiana

Towards the development of a potential remediation technology for multiple heavy metals [Zn(II), Cu(II), Cd(II), Cr(VI) and Ni(II)] from contaminated water, present study examined the growth kinetics and heavy metal removal ability of Beauveria bassiana in individual and multi metals. The specific growth rate of B. bassiana varied from 0.025h(-1) to 0.039h(-1) in presence of individual/multi heavy metals. FTIR analysis indicated the involvement of different surface functional groups in biosorption of different metals, while cellular changes in fungus was reflected by various microscopic (SEM, AFM and TEM) analysis. TEM studies proved removal of heavy metals via sorption and accumulation processes, whereas AFM studies revealed increase in cell surface roughness in fungal cells exposed to heavy metals. Present study delivers first report on the mechanism of bioremediation of heavy metals when present individually as well as multi metal mixture by entomopathogenic fungi.

Surface Modification of Naturally Available Biomass for Enhancement of Heavy Metal Removal Efficiency, Upscaling Prospects, and Management Aspects of Spent Biosorbents: A Review

Heavy metal pollution in water emerges as a severe socio-environmental problem originating primarily from the discharge of industrial wastewater. In view of the toxic, non-biodegradable, and persistent nature of most of the heavy metal ions, remediation of such components becomes an absolute necessity. Biosorption is an emerging tool for bioremediation that has gained momentum for employing low-cost biological materials with effective metal binding capacities. Even though biological materials possess excellent metal adsorption abilities, they show poor mechanical strength and low rigidity. Other disadvantages include solid-liquid separation problems, possible biomass swelling, lower efficiency for regeneration or reuse, and frequent development of high pressure drop in the column mode that limits its applications under real conditions. To improve the biosorption efficiency, biomasses need to be modified with a simple technique for selective/multi-metal adsorption. This review is intended to cover discussion on biomass modification for enhanced biosorption efficiency, mechanism studies using various instrumental/analytical techniques, and future direction for research and development including the fate of spent biosorbent. In most of the previously published researches, difficulty of the process in scaling up has not been addressed. The current article outlines the application potential of biosorbents in the development of hybrid technology integrated with membrane processes for water and wastewater treatment in industrial scale.

Metabolic biotransformation of copper-benzo[a]pyrene combined pollutant on the cellular interface of Stenotrophomonas maltophilia

Previous studies have confirmed that Stenotrophomonas maltophilia can bind an appreciable amount of Cu(II) and degrade BaP. However, the removal mechanisms of Cu(II) coexisted with BaP by S. maltophilia are still unclear. In this study, the micro-interaction of contaminants on the cellular surface was investigated. The results indicated that carboxyl groups played an important role in the binding of copper to the thallus and that the cell walls were the main adsorption sites. Nevertheless, these reactive groups had no obvious effect on the uptake of BaP. Instead, the disruption and modification of cell walls accelerated transportation of BaP across the membrane into cells. The observation of SEM-EDS confirmed that Cu(II) would be adsorbed and precipitated onto the cell surface but would also be removed by extracellular precipitation when BaP coexisted. And the XPS analysis reflected that part of Cu(II) bound onto biosorbents changed into Cu(I) and Cu.

Biomineralization of Pb(II) into Pb-hydroxyapatite induced by Bacillus cereus 12-2 isolated from Lead-Zinc mine tailings

The remediation of Pb(II) through biomineralization is rergarded as a promising technique as well as an interesting phenomenon for transforming heavy metals from mobile species into very stable minerals in the environment. Studies are well needed for in-depth understanding the mechanism of Pb(II) immobilized by bacteria. In the present study, we investigated the uptake and biomineralization of Pb(II) using Bacillus cereus 12-2 isolated from lead-zinc mine tailings. The maximum Pb(II) uptake capacity of B. cereus 12-2 was 340 mg/g at pH 3.0. Zeta potential analyses and selective passivation experiments demonstrated that electrostatic attraction was the main force driving the uptake of Pb(II), while the carboxyl, amide and phosphate functional groups of the bacteria provided the binding sites for immobilizing Pb(II). XRD and TEM investigation revealed that the Pb(II) loaded on bacteria could be stepwise transformed into rod-shaped Ca2.5Pb7.5(OH)2(PO4)6 nanocrystal. Combined with protein denaturalization experiments, we proposed that the biomineralization of Pb(II) possibly consisted of two steps: (1) Rapid biosorption of Pb(II) on B. cereus 12-2 through the synergy of electrostatic attraction, ionic exchange and chelating activity of functional groups; (2) enzyme-mediated mineral transformation from amorphous precipitate to rod-shaped crystalline minerals happening gradually inside the bacteria.

Synthesis of a functionalized fibrous adsorbent of high uptake capacity: a study on Pb(ii) uptake and simple acidic site model development

Development and exposure of acidic functional groups on lignocellulose biomaterials through destruction of lignin barrier by acid treatment.

Investigation of adsorption and photocatalytic activities of in situ cetyltrimethylammonium bromide-modified Bi/BiOCl heterojunction photocatalyst for organic contaminants removal

Bi/BiOCl heterojunction was prepared via a hydrothermal method, using cetyltrimethylammonium bromide (CTAB) as a stabilizing agent.