Statistical modeling and optimization of the cadmium biosorption process in an aqueous solution using Aspergillus niger

Technological trends in nanosilica synthesis and utilization in advanced treatment of water and wastewater

Water and wastewater treatment applications stand to benefit immensely from the design and development of new materials based on silica nanoparticles and their derivatives. Nanosilica possesses unique properties, including low toxicity, chemical inertness, and excellent biocompatibility, and can be developed from a variety of sustainable precursor materials. Herein, we provide an account of the recent advances in the synthesis and utilization of nanosilica for wastewater treatment. This review covers key physicochemical aspects of several nanosilica materials and a variety of nanotechnology-enabled wastewater treatment techniques such as adsorption, separation membranes, and antimicrobial applications. It also discusses the prospective design and tuning options for nanosilica production, such as size control, morphological tuning, and surface functionalization. Informative discussions on nanosilica production from agricultural wastes have been offered, with a focus on the synthesis methodologies and pretreatment requirements for biomass precursors. The characterization of the different physicochemical features of nanosilica materials using critical surface analysis methods is discussed. Bio-hybrid nanosilica materials have also been highlighted to emphasize the critical relevance of environmental sustainability in wastewater treatment. To guarantee the thoroughness of the review, insights into nanosilica regeneration and reuse are provided. Overall, it is envisaged that this work's insights and views will inspire unique and efficient nanosilica material design and development with robust properties for water and wastewater treatment applications.

Biosorption of Cu2+, Pb2+, Cd2+ and their mixture from aqueous solutions by Michelia figo sawdust

The study aimed at investigating copper, lead, and cadmium removal from both single and mixed metal solutions by Michelia figo (Lour.) Spreng. wood sawdust treated with 0.5 mol l⁻¹ NaOH for four hours. In order to evaluate the effects of each factor and interactions between factors on metal ion biosorption, a 2³ factorial experimental design was applied. FTIR results showed that the metal ions would bind to the hydroxyl and carboxyl groups of M. figo wood sawdust biomass. The main effects and interactions of three factors pH (3 and 5), initial metal ion concentration (C₀, 0.157 and 1.574 mmol L⁻¹), and dosage of biomass (D, 4 and 10 g L⁻¹) at two levels were analyzed. The most significant variable regarding Cu²⁺ and Pb²⁺ biosorption was initial metal iron concentration. For Cd²⁺, pH was found to be the most significant factor. The maximum removal efficiencies were 94.12 and 100% for Cu²⁺ and Cd²⁺, respectively, at conditions of (+ 1, − 1, + 1): pH 5, initial metal concentration 0.157 mmol L⁻¹ and dosage of biomass 10 g L⁻¹, while 96.39% for Pb²⁺ at conditions of (− 1, − 1, + 1): pH 3, initial metal concentration 0.157 mmol L⁻¹ and dosage of biomass 10 g L⁻¹. There were some interactions between factors: pH*C₀ and C₀*D for Cu²⁺, pH*C₀, pH*D and C₀*D for Pb²⁺, pH*C₀ and C₀*D for Cd²⁺. Biosorption from a multi metal system showed that the presence of Cu²⁺ and Cd²⁺ had no significant influence on the Pb²⁺ removal, while Pb²⁺ in solution significantly decreased the removal efficiencies of the other two metals.

Fungal remediation of Cd(ii) from wastewater using immobilization techniques

The pollution of wastewater by heavy metal ions is hazardous to the environment and human health. Cd(ii) has been recognized as one of the heavy metals that causes severe toxic effects. The present study is aimed at removing Cd(ii) from wastewater using fungal biomass either immobilized on loofa sponges or in Ca-alginate beads. Two fungal species were isolated from pools of Cd(ii)-polluted wastewater obtained from some Egyptian industrial plants, and using internal transcribed spacer (ITS) primers, they were molecularly identified as Penicillium chrysogenum and Cephalotheca foveolata with accession numbers MT664773 and MT664745, respectively. The sorbents used in this study were heat-inactivated mycelia of P. chrysogenum (PEN), heat-inactivated mycelia of C. foveolata (CEP), P. chrysogenum immobilized on loofa sponge (PEN-ILS), C. foveolata immobilized on loofa sponge (CEP-ILS), P. chrysogenum immobilized in Ca-alginate beads (PEN-IA), and C. foveolata immobilized in Ca-alginate beads (CEP-IA). The effects of pH, contact time, initial Cd(ii) concentration, and interfering ions on Cd(ii) removal from aqueous solution were tested. Maximum Cd(ii) sorption capacity was obtained at pH 7.0, with thirty minutes contact time and 0.5 mol l⁻¹ initial Cd(ii) concentration for all sorbents used. However, Ca²⁺ displayed synergistic interference with Cd(ii) that was greater than that from Na⁺ and K⁺, with decreasing sorption capacity for all sorbents. Optimum conditions were applied to real wastewater samples collected from two Egyptian industrial plants. All sorbents had the ability to remove Cd(ii) from wastewater samples, and enhanced removal occurred when fungal cells were immobilized as compared to free cells.

The pollution of wastewater by heavy metal ions is hazardous to the environment and human health.

Self-assembly biochar colloids mycelial pellet for heavy metal removal from aqueous solution

To effectively improve the heavy metal removal efficiency and stability of biomass adsorbents, a novel biochar colloids-mycelial pellets (BC-MP) composite was prepared via a biological assembly method. BC-MP was successfully produced with increased surface area and multisorption sites by physical adsorption, electrostatic interaction and hydrogen-bond formation between BC and extracellular polymers on MP. To investigate the performance and mechanisms of heavy metal adsorption by BC-MP, batch experiments were conducted with cadmium (Cd (II)) as the model pollutant. Results showed that BC-MP had higher removal efficiency (57.66%) compared to BC (5.45%) and MP (38.45%), respectively, due to the synergistic effect. The maximum adsorption capacity of Cd (II) on BC-MP was 102.04 mg/g based on Langmuir isotherm model. Adsorption kinetics analysis indicated that chemical sorption was the key factor controlling the adsorption of Cd (II) onto BC-MP. Multiple characterization tests revealed that the main mechanisms of the adsorption process were surface complexation, cation exchange and precipitation. The BC-MP composite showed excellent heavy metal removal efficiency with long-term adsorption stability, suggesting its potential as a promising biosorbent for heavy metal removal from industrial wastewater.

Optimization of cadmium biosorption by Shewanella putrefaciens using a Box-Behnken design

Microbial adsorption of heavy metals has been attracted more interest in the recent years. However, there are very few studies in investigating the biosorption of heavy metals by Shewanella putrefaciens, which is a metal reducing bacterium. Firstly, the effects of contact time, pH value, temperature, biomass dosage and initial cadmium concentration on the cadmium adsorption by Shewanella putrefaciens were studied by single factor experiments. Then, the response surface methodology (RSM) based on Box-Behnken design was used to optimize the cadmium adsorption by Shewanella putrefaciens. The results showed that the empirical model was suitable for experimental data, and the maximum cadmium removal efficiency by Shewanella putrefaciens was 86.54% under the optimum conditions of contact time 4.0 days, pH value 5, initial cadmium concentration of 20 mg/L, which was further verified by experiments. In addition, scanning electron microscope - Energy Dispersive Spectrometer (SEM-EDS) analysis showed that the bacteria were seriously deformed, and a "bamboo" shape was observed on the surface which consisted of cadmium according to the EDS analysis. Fourier transform infrared spectroscopy (FT-IR) analysis was used to evaluate the possible functional groups involving in interaction between cells and metal ions. The results showed that the distribution of cadmium on the cell surface was related to the carboxyl, amide, hydroxyl and phosphoric acid groups of Shewanella putrefaciens. These studies can provide a comprehensive understanding of the process and mechanism of microbial removal of heavy metals, and theoretical support for the follow-up practice of using biological adsorbents to remediate heavy metal contaminated soil.

Norepinephrine-functionalised nanoflower-like organic silica as a new adsorbent for effective Pb(II) removal from aqueous solutions

In order to remove Pb(II) ions efficiently from aqueous solutions, a new effective adsorbent of norepinephrine-functionalised nanoflower-like organic silica (NE-NFOS) was synthesised by a biomimetic method. Biomimetic functionalization with norepinephrine has the advantages of environment-friendly and easy operation. Characterization of the NE-NFOS using scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller method, and Fourier-transform infrared spectroscopy revealed that the NFOS was modified successfully by norepinephrine. Furthermore, the influences of different parameters including adsorption kinetics, solution pH, adsorption isotherms, concentrations of Na+, K+, Ca2+, and Mg2+, desorption and reusability were studied. The adsorption experiments showed that the capacity of NE-NFOS to adsorb Pb(II) ions improved greatly after functionalisation and adsorption equilibrium was attained within 90 min at a pH of 6.0. The Na+, K+, Ca2+, and Mg2+ concentrations had little influence on the adsorption, and after recycling for five times, the Pb(II) ion removal efficiency of the adsorbent was more than 79% of its initial value. Thus, it was demonstrated that the NE-NFOS with excellent adsorption performance could be a suitable adsorbent for Pb(II) ions removal in practical applications.

Response mechanism of mine-isolated fungus Aspergillus niger IOC 4687 to copper stress determined by proteomics

Proteomic analysis of the fungus Aspergillus niger showed that its capacity to absorb metals was boosted by physiological modification under metal stress conditions.

Kinetics, isotherm, and optimization of the hexavalent chromium removal from aqueous solution by a magnetic nanobiosorbent

Sorption is the most effective approach to the treatment of acid mine drainage (AMD) and wastewaters, but the removal of the adsorbents from water has always been a challenging problem which may be resolved by using magnetic separation. In this work, a magnetic bioadsorbent was prepared using low cost and high-performance sources and applied in Cr(VI) removal from a synthetic solution. Initially, magnetite nanoparticles were synthesized from iron boring scraps by chemical co-precipitation method. Results of dynamic light scattering (DLS) and vibrating sample magnetometry (VSM) analyses showed that the synthesized nanoparticles were around 40 nm in size and had a significant magnetization. Then, the magnetite nanoparticles were attached to the dead and alkaline activated biomass of Aspergillus niger. Central composite design (CCD) was applied to determine the optimal condition of Cr(VI) adsorption on the produced magnetic nanobiocomposite. The maximum chromium removal (~ 92%) was achieved at pH 5.8, Cr concentration 23.4 mg/l, adsorbent dose 3.72 g/l, agitation rate 300 rpm, and duration 11 min. Kinetic studies showed that regardless of temperature, the process was controlled by mass transfer and intraparticle diffusion with an equilibrium constant of 0.74 mg/g min^1/2 at 40 °C. Also, the adsorption isotherms followed the Temkin model, which indicated the physical adsorption of Cr(VI) on the produced sorbent. Therefore, the magnetic nanobiocomposite has a perfect ability to be used as the chromium adsorbent and can be collected by a low external magnetic field. Graphical abstract Synthesis of the magnetic nanobiosorbent and its application in the removal of Cr(VI) from wastewaters.

Optimization of copper, lead and cadmium biosorption onto newly isolated bacterium using a Box-Behnken design

Due to the progressive development of industrial and technological activities, heavy metal contamination is increasing each year and it poses a serious health and environmental risk. Microorganisms are capable of removing heavy metals from a contaminated environment. In this work, 51 microbial strains were isolated from heavy metal contaminated water and soil. The JAW1 strain, identified as Pseudomonas azotoformans, was selected and applied in bioremediation of the specific mixture of metals (Cd, Cu, and Pb) in an aqueous medium. The Box-Behnken design was used to optimize the biosorption process, with three factors: pH, initial metal concentration, concentration of the biosorbent. For the strain P. azotoformans JAW1, the optimal conditions were pH = 6.0, 25mg/L of each metal and 2g/L, following removal levels were achieved: Cd 44,67%; Cu 63,32%; Pb 78,23%. The possible interactions of cell-metal ions were evaluated using FT-IR analysis. The study indicated the presence of groups, which may be responsible for bonding of metal ions. The studies conducted on bioremediation mechanisms indicated that metal accumulation could occur on the cell surface (biosorption) where the amount of adsorbed metals reached: Cd 98,57%, Cu 69,76%, Pb 88,58%. P. azotoformans JAW1 exhibited a potential for application in the bioremediation of mining wastewater with complex metal contaminations.

Adsorption of heavy metals on conventional and nanostructured materials for wastewater treatment purposes: A review

The problem of water pollution is of a great concern. Adsorption is one of the most efficient techniques for removing noxious heavy metals from the solvent phase. This paper presents a detailed information and review on the adsorption of noxious heavy metal ions from wastewater effluents using various adsorbents - i.e., conventional (activated carbons, zeolites, clays, biosorbents, and industrial by-products) and nanostructured (fullerenes, carbon nanotubes, graphenes). In addition to this, the efficiency of developed materials for adsorption of the heavy metals is discussed in detail along with the comparison of their maximum adsorption capacity in tabular form. A special focus is made on the perspectives of further wider applications of nanostructured adsorbents (especially, carbon nanotubes and graphenes) in wastewater treatment.

Bio-prospectus of cadmium bioadsorption by lactic acid bacteria to mitigate health and environmental impacts

Foodstuffs and water are the key sources of cadmium biomagnifiaction. The available strategies to mitigate this problem are unproductive and expensive for practical large-scale use. Biological decontamination of metals through environmental microbes has been known since long time, whereas lactic acid bacteria (LAB) have not been extensively studied for this purpose. The LAB are known for maintaining homeostasis and suppression of pathogens in humans and animals. They also play a vital role in bioremediation of certain heavy metals. Recently in-vivo research findings strongly complement the in-vitro results in relation to decreased total body cadmium burden in animal model. This review summarizes the currently available information on impact of toxic metal (Cd) on human and animal health as well as cadmium sequestration through microbes placed broadly, whereas preeminent attention grabbed on LAB-cadmium interaction to explore their possible role in bioremediation of cadmium from foods and environment to safeguard human as well as environment health.

Response surface modeling of lead (׀׀) removal by graphene oxide-Fe3O4 nanocomposite using central composite design

BACKGROUND

Magnetic graphene oxide (Fe3O4@SiO2-GO) nanocomposite was fabricated through a facile process and its application as an excellent adsorbent for lead (II) removal was also demonstrated by applying response surface methodology (RSM).

METHODS

Fe3O4@SiO2-GO nanocomposite was synthesized and characterized properly. The effects of four independent variables, initial pH of solution (3.5-8.5), nanocomposite dosage (1-60 mg L(-1)), contact time (2-30 min), and initial lead (II) ion concentration (0.5-5 mg L(-1)) on the lead (II) removal efficiency were investigated and the process was optimized using RSM. Using central composite design (CCD), 44 experiments were carried out and the process response was modeled using a quadratic equation as function of the variables.

RESULTS

The optimum values of the variables were found to be 6.9, 30.5 mg L(-1), 16 min, and 2.49 mg L(-1) for pH, adsorbent dosage, contact time, and lead (II) initial concentration, respectively. The amount of adsorbed lead (II) after 16 min was recorded as high as 505.81 mg g(-1) for 90 mg L(-1) initial lead (II) ion concentration. The Sips isotherm was found to provide a good fit with the adsorption data (KS = 256 L mg(-1), nS = 0.57, qm = 598.4 mg g(-1), and R(2) = 0.984). The mean free energy Eads was 9.901 kJ/mol which confirmed the chemisorption mechanism. The kinetic study determined an appropriate compliance of experimental data with the double exponential kinetic model (R(2) = 0.982).

CONCLUSIONS

Quadratic and reduced models were examined to correlate the variables with the removal efficiency of Fe3O4@SiO2-GO. According to the analysis of variance, the most influential factors were identified as pH and contact time. At the optimum condition, the adsorption yield was achieved up to nearly 100 %.

Optimization of the condition for adsorption of gallic acid by Aspergillus oryzae mycelia using Box-Behnken design

Fresh biomass of Aspergillus oryzae (A. oryzae) CGMCC5992 can effectively remove gallic acid from aqueous solution. To improve the removal rate of gallic acid, this study first identified the important factors affecting the removal rate of gallic acid with univariate analysis, and then used four-factor and three-level Box-Behnken design (BBD) with the removal rate of gallic acid as response value, to obtain the optimum conditions for the removal of gallic acid as follows: 6.95 h treatment time, pH 3.70, 7.07 g/L mycelium volume, and 120.64 mg/L initial concentration of gallic acid. Under such optimized condition, the removal rate of gallic acid approached 99.21 %. HPLC-MS analysis proved that the gallic acid in aqueous solution was completely removed by A. oryzae, rather than being metabolized into its derivatives. Scanning electron microscopy (SEM) indicated that the biomass morphology and surface structure of A. oryzae changed after the adsorption of gallic acid. Thus, the present study has provided an optimal condition for A. oryzae removal of gallic acid in water.

Bioremediation of heavy metal contaminated aqueous solution by using red algae Porphyra leucosticta

Bioremediation is an effective process for the removal and recovery of heavy metal ions from aqueous solutions. In this study, red algae Porphyra leucosticta was examined to remove Cd(II) and Pb(II) ions from wastewater through biological enrichment and biological precipitation. The experimental parameters that affect the bioremediation process such as pH, contact time and biomass dosage were studied. The maximum bioremediation capacity of metal ions was 31.45 mg/g for Cd(II) and 36.63 mg/g for Pb(II) at biomass dosage 15 g/L, pH 8.0 and contact time 120 minutes containing initial 10.0 mg/L of Cd(II) and 10.0 mg/L of Pb(II) solution. Red algae Porphyra leucosticta biomass was efficient at removing metal ions of 10.0 mg/L of Cd(II) and 10.0 mg/L of Pb(II) solution with bioremediation efficiency of 70% for Cd(II) and 90% for Pb(II) in optimal conditions. At the same time, the removal capacity for real industrial effluent was gained at 75% for 7.6 mg/L Cd(II) and 95% for 8.9 mg/L Pb(II). In conclusion, it is demonstrated that red algae Porphyra leucosticta is a promising, efficient, cheap and biodegradable sorbent biomaterial for reducing heavy metal pollution in the environment and wastewater.

Experimental design for the optimization of copper biosorption from aqueous solution by Aspergillus terreus

An experimental design methodology was applied to study the effects of temperature, pH, biomass dose, and stirring speed on copper removal from aqueous solutions by Aspergillus terreus in a biosorption batch system. To identify the effects of the main factors and their interactions on copper removal efficiency and to optimize the process, a full 2(4) factorial design with central points was performed. Four factors were studied at two levels, including stirring speed (50-150 min(-1)), temperature (30-50°C), pH (4-6) and biosorbent dose (0.01-0.175 g). The main factors observed were pH and biomass dose, along with the interactions between pH and biomass, and stirring speed. The optimal operational conditions were obtained using a response surface methodology. The adequacy of the proposed model at 99% confidence level was confirmed by its high adjusted linear coefficient of determination (R(Adj)(2)=0.9452). The best conditions for copper biosorption in the present study were: pH 6, biosorbent dose of 0.175 g, stirring speed of 50 min(-1) and temperature of 50°C. Under these conditions, the maximum predicted copper removal efficiency was 68.52% (adsorption capacity of 15.24 mg/g). The difference between the experimental and predicted copper removal efficiency at the optimal conditions was 4.8%, which implies that the model represented very well the experimental data.

High performance SiO2-nanoparticles-immobilized-Penicillium funiculosum for bioaccumulation and solid phase extraction of lead

Novel biosorbent systems were designed, investigated and implemented for bioaccumulation of Pb(II) from aqueous solutions. These are based on the combination of SiO(2)-nanoparticles (N-Si) with Penicillium funiculosum fungus (Pen) for the formation of (N-Si-Pen) as well as heat inactivated Penicillium funiculosum (Pen). The SiO(2)-nanoparticles were also investigated as a solid sorbent phase. Surface characterization and immobilization were examined and confirmed by using FT-IR and SEM analysis. A batch equilibrium technique was used to follow-up the adsorption processes of lead under the effect of pH, contact time, sorbent dosage and initial metal concentration. The maximum capacity values were 1200.0 and 1266.7μmolg(-1) for (Pen) and (N-Si-Pen), respectively at pH 5. Sorption equilibria were established in ∼20min and their data were well described by Langmuir, Freundlich and Dubinin-Radushkevich models. The potential applications of these biosorbents for extraction of Pb(II) from real samples contaminated with lead, were successfully accomplished.

Removal of heavy metal ions from wastewaters: a review

Heavy metal pollution has become one of the most serious environmental problems today. The treatment of heavy metals is of special concern due to their recalcitrance and persistence in the environment. In recent years, various methods for heavy metal removal from wastewater have been extensively studied. This paper reviews the current methods that have been used to treat heavy metal wastewater and evaluates these techniques. These technologies include chemical precipitation, ion-exchange, adsorption, membrane filtration, coagulation-flocculation, flotation and electrochemical methods. About 185 published studies (1988-2010) are reviewed in this paper. It is evident from the literature survey articles that ion-exchange, adsorption and membrane filtration are the most frequently studied for the treatment of heavy metal wastewater.

Characterization of copper bioreduction and biosorption by a highly copper resistant bacterium isolated from copper-contaminated vineyard soil

Copper is an essential but toxic heavy metal that negatively impacts living systems at high concentration. This study presents factors affecting copper bioremoval (bioreduction and biosorption) by a highly copper resistant monoculture of Pseudomonas sp. NA and copper bioremoval from soil. Seven bacteria resistant to high concentration of Cu(II) were isolated from enrichment cultures of vineyard soils and mining wastes. Culture parameters influencing copper bioreduction and biosorption by one monoculture isolate were studied. The isolate was identified by 16S rRNA gene sequence analysis as a Pseudomonas sp. NA (98% similarity to Pseudomonas putida, Pseudomonas plecoglossicida and other Pseudomonas sp.). The optimal temperature for growth was 30 degrees C and bioremoval of Cu(II) was maximal at 35 degrees C. Considerable growth of the isolate was observed between pH 5.0 and 8.0 with the highest growth and biosorption recorded at pH 6.0. Maximal bioreduction was observed at pH 5.0. Cu(II) bioremoval was directly proportional to Cu(II) concentration in media. Pseudomonas sp. NA removed more than 110mg L(-1) Cu(II) in water within 24h through bioreduction and biosorption at initial concentration of 300mg L(-1). In cultures amended with 100mg L(-1), 20.7mg L(-1) of Cu(II) was biologically reduced and more than 23mg L(-1) of Cu(II) was biologically removed in 12h. The isolate strongly promoted copper bioleaching in soil. Results indicate that Pseudomonas sp. NA has good potential as an agent for removing copper from water and soil.

Biosorption equilibria of binary Cd(II) and Ni(II) systems onto Saccharomyces cerevisiae and Ralstonia eutropha cells: application of response surface methodology

Present study investigated the biosorption of Cd(II) and Ni(II) from aqueous solution onto Saccharomyces cerevisiae and Ralstonia eutropha non-living biomass. Biomass inactivated by heat and pretreated by ethanol was used in determination of optimum conditions. The important process parameters, such as initial solution pH (2-8), initial Ni(II) concentration (11-42 mg/l), initial Cd(II) concentration (11-42 mg/l), and biomass dosage (0.2-4.7 g/l) were optimized using design of experiments (DOE). A central composite design (CCD) under response surface methodology (RSM) was applied to evaluate and optimize the efficiency of removing each adsorbent. Moreover, the two responses were simultaneously studied by using a numerical optimization methodology. The optimum removal efficiency of Cd(II) and Ni(II) onto S. cerevisiae was determined as 43.4 and 65.5% at 7.1 initial solution pH, 4.07 g/l biomass dosage, 16 mg/l initial Ni(II) concentration and 37 mg/l initial Cd(II) concentration. The optimum removal efficiency of Cd(II) and Ni(II) onto R. eutropha was ascertained as 52.7 and 50.1% at 5.0 initial solution pH, 2.32 g/l biomass dosage, 28 mg/l initial Ni(II) concentration and 37 mg/l initial Cd(II) concentration. The present analysis suggests that the predicted values are in good agreement with experimental data. The characteristics of the possible interactions between biosorbents and metal ions were also evaluated by scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy analysis.

Biosorption of nickel(II) from aqueous solution by Aspergillus niger: response surface methodology and isotherm study

In the present study, the effects of biosorbent Aspergillus niger dosage, initial solution pH and initial Ni(II) concentration on the uptake of Ni(II) by NaOH pretreated biomass of A. niger from aqueous solution were investigated. Batch experiments were carried out in order to model and optimize the biosorption process. The influence of three parameters on the uptake of Ni(II) was described using a response surface methodology (RSM) as well as Langmuir and Freundlich isotherm models. Optimum Ni(II) uptake of 4.82 mg Ni(II)g(-1) biomass (70.30%) was achieved at pH 6.25, biomass dosage of 2.98 gL(-1) and initial Ni(II) concentration of 30.00 mgL(-1) Ni(II). Langmuir and Freundlich were able to describe the biosorption isotherm fairly well. However, prediction of Ni(II) biosorption using Langmuir and Freundlich isotherms was relatively poor in comparison with RSM approaches. The biosorption mechanism was also investigated by using Fourier transfer infrared (FT-IR) analysis of untreated, NaOH pretreated, and Ni(II) loaded A. niger biomass.