Biosorption of Copper by Paenibacillus polymyxa Cells and their Exopolysaccharide

Summary Biosorption of heavy metals by gram-positive, non-pathogenic and non-toxicogenic Paenibacillus polymyxa P13 was evaluated. Copper was chosen as a model element because it is a pollutant originated from several industries. An EPS (exopolysaccharide)-producing phenotype exhibited significant Cu(II) biosorption capacity. Under optimal assay conditions (pH 6 and 25 °C), the adsorption isotherm for Cu(II) in aqueous solutions obeyed the Langmuir model. A high q value (biosorption capacity) was observed with whole cells (q_max=112 mgCu g⁻¹). EPS production was associated with hyperosmotic stress by high salt (1 M NaCl), which led to a significant increase in the biosorption capacity of whole cells (q_max=150 mgCu g⁻¹). Biosorption capacity for Cu(II) of the purified EPS was investigated. The maximum biosorption value (q) of 1602 mg g⁻¹ observed with purified EPS at 0.1 mg ml⁻¹ was particularly promising for use in field applications.     

Biosorption of heavy metals by lyophilized cells of <Emphasis Type="Italic">Pseudomonas stutzeri</Emphasis>

Biosorptive capacity of Pb(II), Cd(II) and Cu(II) by lyophilized cells of Pseudomonas stutzeri was investigated based on Langmuir and Freundlich isotherms. Biosorptive capacity for Pb(II), Cd(II) and Cu(II) decreased with an increase of metal concentration, reaching 142, 43.5 and 36.2 mg/g at initial concentration of 300 mg/l, respectively. Biosorption capacity for metal ions increased with increasing pH. The optimum pH for biosorption rate of Cd(II) and Cu(II) were 5.0, and 6.0 for Pb(II) biosorption. The experimental data showed a better fit with the Langmuir model over the Freundlich model for metal ions throughout the range of initial concentrations. The maximum sorptive capacity (q _max) obtained from the Langmuir equation for Pb(II), Cd(II) and Cu(II) were 153.3 (r ²  = 0.998), 43.86 (r ²  = 0.995), and 33.16 (r ²  = 0.997) for metal ions, respectively. The selectivity order for metal ions towards the biomass of P. stutzeri was Pb(II) > Cd(II) > Cu(II) for a given initial metal ions concentration. The interactions between heavy metals and functional groups on the cell wall surface of bacterial biomass were confirmed by FTIR analysis. The results of this study indicate the possible removal of heavy metals from the environment by using lyophilized cells of P. stutzeri.     

Cadmium uptake by algal biomass in batch and continuous (CSTR and packed bed column) adsorbers

In this work, the properties of marine algae Gelidium, algal waste from agar extraction industry and a composite material were investigated for cadmium(II) biosorption. Equilibrium experiments were performed at three pH values (4, 5.3 and 6.5). Equilibrium data were well described by the Langmuir and Langmuir–Freundlich isotherms. Two models predicting the pH influence in the cadmium biosorption (discrete and continuous models) have been developed in order to better describe the equilibrium. The continuous model also considers a heterogeneous distribution of carboxylic groups, determined by potentiometric titration. The results of batch kinetic experiments performed at different pH values were well fitted by two mass transfer models and the homogeneous diffusion coefficients for the cadmium ions inside the biosorbent were obtained. Continuous stirred tank reactor (CSTR) and packed bed column configurations were also examined for the biosorption of cadmium ions. A strong acid (0.1 M HNO₃) was used as eluant to regenerate the biosorbents in the column. Several mass transfer models were applied with success to describe the biosorption process in batch mode, CSTR and fixed bed column.     

Continuous biosorption of cadmium by Moringa olefera in a packed column

The biosorption of Cd(II) by Moringa oleifera using a batch system and a continuous up flow mode in a fixed bed column was studied. Batch adsorption experiments were performed as a function of pH, biosorbent dose, contact time, volume of the solution, and initial metal concentration. The adsorption isotherms obtained fitted well into the Freundlich and Langmuir isotherms. The dynamic removal of cadmium by powdered seed of the Moringa oleifera was studied in a packed column. The effect of bed height (4 and 8 cm) and flow rate (2 and 5mL/min) on biosorption process was investigated and the experimental breakthrough curves were obtained. Results showed that by increasing the bed height and decreasing the flow rate, the breakthrough and exhaustion times increased. The break-through time was considered as a measure of the column performance. The maximum break-through time of 320 min was achieved at the operating condition of 2 mL/min influent flow rate and bed height of 8 cm.     

The mechanism of cadmium removal from aqueous solution by nonmetabolizing free and immobilized live biomass of Rhizopus oligosporus

A preliminary study on the removal of cadmium by nonmetabolizing live biomass of Rhizopus oligosporus from aqueous solution is presented. The equilibrium of the process was in all cases well described by the Langmuir sorption isotherm, suggesting that the process was a chemical, equilibrated and saturable mechanism which reflected the predominantly site-specific mechanism on the cell surface. A curve of Scatchard transformation plots reflected the covalent nature of Cd²⁺ adsorption by the cells. The maximum cadmium uptake capacities were 34.25 mg/g for immobilized cells and 17.09 mg/g for free cells. Some factorial experiments in shake flasks were performed in order to investigate the effect of different initial cadmium concentrations and biomass concentrations on the equilibrium. Experimental results showed a reverse trend of the influence of the immobilized and free biomass concentration on the cadmium specific uptake capacity. The immobilized cells had a higher specific cadmium uptake capacity with increasing biomass concentrations compared to free cells. In a bioreactor, the cadmium uptake capacity of immobilized cells (q_max = 30.1–37.5 mg/g) was similar to that observed in shake flask experiments (q_max = 34.25 mg/g) whereas with free cells the bioreactor q_max of 4.8–13.0 mg/g; was much lower than in shake flasks (q_max = 17.09 mg/g), suggesting that cadmium biosorption by immobilized cells of R. oligosporus might be further improved in bigger reactors. EDAX and transmission electron microscopic experiments on the fungal biomass indicated that the presence of Cd²⁺ sequestrated to the cell wall was due to bioadsorption.     

Removal of malachite green (MG) from aqueous solutions by native and heat-treated anaerobic granular sludge

The performance of native and heat-treated anaerobic granular sludge in removing of malachite green (MG) from aqueous solution was investigated with different conditions, such as pH, ionic strength, initial concentration and temperature. The maximum biosorption was both observed at pH 5.0 on the native and heat-treated anaerobic granular sludge. The ionic strength had negative effect on MG removal. Kinetic studies showed that the biosorption process followed pseudo-second-order and q_e for native and heat-treated anaerobic granular sludge is 61.73 and 59.17 mg/g at initial concentration 150 mg/L, respectively. Intraparticle diffusion model could well illuminate adsorption process and faster adsorption rate of native anaerobic granular sludge than heat-treated anaerobic granular sludge. The equilibrium data were analyzed using Langmuir and Freundlich model, and well fitted Langmuir model. The negative values of ΔG° and ΔH° suggested that the interaction of MG adsorbed by native and heat-treated anaerobic granular sludge was spontaneous and exothermic. Desorption studies revealed that MG could be well removed from anaerobic granular sludge by 1% (v/v) of HCl–alcohol solution.     

A breakthrough column study for removal of malachite green using coco-peat

Abstract

A continuous adsorption study in a fixed bed column using coco-peat (CP) as an adsorbent was carried out for the removal of toxic malachite green (MG) from contaminated water. Fixed bed column studies were carried out to check field application viability. Various parameters like particle size, pH, concentration, dose and interference were exercised to optimize dye removal. Data obtained from breakthrough column studies were evaluated using Thomas and BDST model. Thomas rate constants K_t (0.22?ml min^?1 mg^?1) and adsorption capacity q_o (181.04?mg g^?1) were estimated and found to favor efficiency of CP. Thomas model was tested with several parameters like flow rate, concentration, and bed depth. Upon increase in input dye concentration, flow rate and bed height, adsorption coefficients increased. According to BDST model, maximum dye uptake of 468.26?mg/l was obtained with an input dye concentration of 5?mg/l. HYBRID and MPSD error functions were tested and found that Thomas model fits best. Dilute hydrochloric acid was found best for desorption. Real wastewater from textile industry was analyzed and confirmed the prospect of large-scale industrial application. In conclusion, coco-peat can be used as a promising bio-sorbent in column bed for scavenging of MG from contaminated water.     

Biosorption of Fe3+ from aqueous solution by a bacterial dead Streptomyces rimosus biomass

The iron biosorption capacity of a Streptomyces rimosus biomass treated with NaOH was studied in batch mode. After pretreatment of biomass at the ambient temperature, optimum conditions of biosorption were found to be: a biomass particle size between 50 and 160 μm, an average saturation contact time of 4 h, a biomass concentration of 3 g/l and a stirring speed of 250 rpm. The equilibrium data could be fitted by Langmuir isotherm equation. Under these optimal conditions, 122 mg _Fe/g_biomass were fixed.     

Biosorption of Ni (II) by Schizosaccharomyces pombe: kinetic and thermodynamic studies

The potential of the dried yeast, wild-type Schizosaccharomyces pombe, to remove Ni(II) ion was investigated in batch mode under varying experimental conditions including pH, temperature, initial metal ion concentration and biosorbent dose. Optimum pH for biosorption was determined as 5.0. The highest equilibrium uptake of Ni(II) on S. pombe, q _e, was obtained at 25 °C as 33.8 mg g⁻¹. It decreased with increasing temperature within a range of 25–50 °C denoting an exothermic behaviour. Increasing initial Ni(II) concentration up to 400 mg L⁻¹ also elevated equilibrium uptake. No more adsorption took place beyond 400 mg L⁻¹. Equilibrium data fitted better to Langmuir model rather than Freundlich model. Sips, Redlich–Peterson, and Kahn isotherm equations modelled the investigated system with a performance not better than Langmuir. Kinetic model evaluations showed that Ni(II) biosorption process followed the pseudo-second order rate model while rate constants decreased with increasing temperature. Gibbs free energy changes (ΔG°) of the system at 25, 30, 35 and 50 °C were found as −1.47E + 4, −1.49E + 4, −1.51E + 4, and −1.58E + 4 J mol⁻¹, respectively. Enthalpy change (ΔH°) was determined as −2.57E + 3 J mol⁻¹ which also supports the observed exothermic behaviour of the biosorption process. Entropy change (ΔS°) had a positive value (40.75 J mol⁻¹ K⁻¹) indicating an increase in randomness during biosorption process. Consequently, S. pombe was found to be a potential low-cost agent for Ni(II) in slightly acidic aqueous medium. In parallel, it has been assumed to act as a separating agent for Ni(II) recovery from its aqueous solution.     

Microwave treated Salvadora oleoides as an eco-friendly biosorbent for the removal of toxic methyl violet dye from aqueous solution—A green approach

In the present study, microwave treated Salvadora oleoides (MW-SO) has been investigated as a potential biosorbent for the removal of toxic methyl violet dye. A batch adsorption method was experimented for biosorptive removal of toxic methyl violet dye from the aqueous solution. The effect of various operating variables, viz., adsorbent dosage, pH, contact time and temperature on the removal of the dye was studied and it was found that nearly 99% removal of the dye was possible under optimum conditions. Kinetic study revealed that a pseudo-second-order mechanism was predominant and the overall process of the dye adsorption involved more than one step. Hence, in order to investigate the rate determining step, intra-particle diffusion model was applied. Adsorption equilibrium study was made by analyzing Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) adsorption isotherm models and the biosorption data was found to be best represented by the Langmuir model. The biosorption efficiency of MW-SO was also compared with unmodified material, Salvadora oleoides (SO). It was found that the sorption capacity (q_max) increased from 58.5 mg/g to 219.7 mg/g on MW treatment. Determination of thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) confirmed the spontaneous, endothermic and feasible nature of the adsorption process. The preparation of MW-SO did not require any additional chemical treatment and a high percentage removal of methyl violet dye was obtained in much lesser time. Thus, it is in agreement with the principles of green chemistry. The results of the present research work suggest that MW-SO can be used as an environmentally friendly and economical alternative biosorbent for the removal of methyl violet dye from aqueous solutions.     

Biosorption of lead and nickel by living and non-living cells of Pseudomonas aeruginosa ASU 6a

The optimum conditions for biosorption and bioaccumulation of lead and nickel were investigated by using a tolerant bacterial strain isolated from El-Malah canal, Assiut, Egypt, and identified as Pseudomonas aeruginosa ASU 6a. The experimental adsorption data were fitted towards the models postulated by Langmuir and Freundlich isotherm equations. The binding capacity by living cells is significantly lower than that of dead cells. The maximum biosorption capacities for lead and nickel obtained by using non-living cells and living cells were 123, 113.6 and 79, 70 mg/g, respectively. The biosorptive mechanism was confirmed by IR analysis and from the identification nature of acidic and basic sites. Moreover, the postulated mechanism was found to depend mainly on ionic interaction and complex formation.     

Comparison of the Adsorption Capabilities of Myriophyllum spicatum and Ceratophyllum demersum for Zinc,Copper and Lead

Industrial wastewaters contain various heavy metal components and therefore threaten aquatic bodies. Heavy metals can be adsorbed by living or non‐living biomass. Submerged aquatic plants can be used for the removal of heavy metals. This paper exhibits the comparison of the adsorption properties of two aquatic plants Myriophyllum spicatum and Ceratophyllum demersum for lead, zinc, and copper. The data obtained from batch studies conformed well to the Langmuir Model. Maximum adsorption capacities (q_max) were obtained for both plant species and each metal. The maximum adsorption capacities (q_max) achieved with M. spicatum were 10.37 mg/g for Cu²⁺, and 15.59 mg/g for Zn²⁺ as well as 46.49 mg/g for Pb²⁺ and with C. demersum they were 6.17 mg/g for Cu²⁺, 13.98 mg/g for Zn²⁺ and 44.8 mg/g for Pb²⁺. It was found that M. spicatum has a better adsorption capacity than C. demersum for each metal tested. Gibbs free energy and the specific surface area based on the q_max values were also determined for each metal.     

Biosorption of acid violet dye from aqueous solutions using native biomass of a new isolate of Penicillium sp.

Laboratory investigation of the potential use of Penicillium sp. as biosorbent for the removal of acid violet dye from aqueous solution was studied with respect to pH, temperature, biosorbent, initial dye concentrations. Penicillium sp. decolourizes acid violet (30 mg l⁻¹) within 12 h agitation of 150 rpm at pH 5.7 and temperature of 35 °C. The pellets exhibited a high dye adsorption capacity (5.88 mg g⁻¹) for acid violet dye over a pH range (4–9); the maximum adsorption was obtained at pH 5.7. The increase of temperature favored biosorption for acid violet, but the optimum temperature was 35 °C. Adsorption kinetic data were tested using pseudo-first-order, pseudo-second-order and kinetic studies showed that the biosorption process follows pseudo-first-order rate kinetics with an average rate constant of 0.312 min⁻¹. Isotherm experiments were conducted to determine the sorbent–desorption behavior of examined dye from aqueous solutions using Langmuir and Freundlich equations. Langmuir parameter indicated a maximum adsorption capacity of 4.32 mg g⁻¹ for acid violet and R_L value of 0.377. Linear plot of log q_e vs log C_e shows that applicability of Freundlich adsorption isotherm model. These results suggest that this fungus can be used in biotreatment process as biosorbent for acid dyes.     

Characterisation of acidic sites of Pseudomonas biomass capable of binding protons and cadmium and removal of cadmium via biosorption

Summary The ability of Pseudomonas aeruginosa to accumulate Cd(II) ions from wastewater industries was experimentally investigated and mathematically modelled. From the potentiometric titration and non-ideal competitive analysis (NICA) model, it was found that the biomass contains three acidic sites. The values of proton binding (pK _i =1.66±3.26×10⁻³, 1.92±1.63×10⁻⁴ and 2.16±3.79×10⁻⁴) and binding constant of cadmium metal ions (pK _M1=1.99±2.45×10⁻³ and pK _M2=1.67±4.08×10⁻³) on the whole surface of biomass showed that protonated functional groups and biosorption of Cd(II) ions could be attributed to a monodentate binding to one acidic site, mainly the carboxylic group. From the isothermal sorption experimental data and Langmuir model, it was also found that the value of Langmuir equilibrium (pK _f) constant is 2.04±2.1×10⁻⁵ suggesting that the carboxyl group is the main active binding site. In addition, results showed that the maximum cadmium capacity (q _max) and affinity of biomass towards cadmium metal ions (b) at pH 5.1 and 20 min were 96.5±0.06 mg/g and 3.40×10⁻³± 2.10×10⁻³, respectively. Finally, interfering metal ions such as Pb(II), Cu(II), Cr(III), Zn(II), Fe(II), Mn(II), Ca(II) and Mg(II) inhibited Cd(II) uptake. Comparing the biosorption of Cd(II) by various Pseudomonas isolates from contaminated environment samples (soil and sewage treatment plant) showed that maximum capacities and equilibrium times were different, indicating that there was a discrepancy in the chemical composition between biomasses of different strains.     

The application of a micro-algal/bacterial biofilter for the detoxification of copper and cadmium metal wastes

In the present study the potential of a biofilter containing a mixture of dried micro-algal/bacterial biomass for removing heavy metals (Cu²⁺, Cd²⁺) from dilute electroplating waste was tested. The biomass was produced in an artificial stream using the effluent of a municipal waste water treatment plant as a nutrient source, with the additional benefit of reducing phosphorus and nitrogen loadings. Baseline batch experiments determined that optimum adsorption for both metals (80–100%) were achieved with the deionized-H₂O conditioned biomass at initial pH 4.0. Other biosorption variables (contact time, initial metal concentration) were also tested. Biosorption data were fitted successfully by the Langmuir model and results showed a high affinity of the used biomass for both metals (q_max 18–31 mg metal/g.d.w). Flow-through column experiments containing Ca-alginate/biomass beads showed that metal adsorption depends also on flow-rate and volume of treated waste. Desorption of both metals with weak acids was very successful (95–100%) but the regeneration of the columns was not achieved due to the destabilization of beads.     

Modeling of Pb(II) adsorption by a fixed-bed column

Removal of Pb(II) from an aqueous environment using biosorbents is a cost-effective and environmentally benign method. The biosorption process, however, is little understood for biosorbents prepared from plant materials. In this study, the biosorption process was investigated by evaluating four adsorption models. A fixed-bed column was prepared using a biosorbent prepared from the aquatic plant Hydrilla verticillata. The effect of bed height and flow rate on the biosorption process was investigated. The objective of the study was to determine the ability of H. verticillata to biosorb Pb(II) from an aqueous environment and to understand the process, through modeling, to provide a basis to develop a practical biosorbent column. Experimental breakthrough curves for biosorption of 50 mg L^?1 aqueous Pb(II) using a fixed-bed column with 1.00 cm inner diameter were fitted to the Thomas, Adams-Bohart, Belter, and bed depth service time (BDST) models to investigate the behavior of each model according to the adsorption system and thus understand the adsorption mechanism. Model parameters were evaluated using linear and nonlinear regression methods. The biosorbent removed 65% (82.39 mg g^?1 of biosorbent) of Pb(II) from an aqueous solution of Pb(NO₃)₂ at a flow rate of 5.0 ml min^?1 in a 10 cm column. Na₂CO₃ was used to recover the adsorbed Pb(II) ions as PbCO₃ from the biosorbent. The Pb(II) was completely desorbed at a bed height of 10.0 cm and a flow rate of 5.0 ml min^?1. Fourier transform infrared (FT-IR) analysis of the native biosorbent and Pb(II)-loaded biosorbent indicated that the hydroxyl groups and carboxylic acid groups were involved in the metal bonding process. The FT-IR spectrum of Pb(II)-desorbed biosorbent showed an intermediate peak shift, indicating that Pb(II) ions were replaced by Na⁺ ions through an ion-exchange process. Of the four models tested, the Thomas and BDST models showed good agreement with experimental data. The calculated bed sorption capacity N₀ and rate constant k_a were 31.7 g L^?1 and 13.6 × 10^?4 L mg^?1 min^?1 for the C_t/C₀ value of 0.02. The BDST model can be used to estimate the column parameters to design a large-scale column.     

Biosorption of an Azo Dye by <Emphasis Type="Italic">Aspergillus niger</Emphasis> and <Emphasis Type="Italic">Trichoderma</Emphasis> sp. Fungal Biomasses

Biosorption is an eco-friendly and cost-effective method for treating the dye house effluents. Aspergillus niger and Trichoderma sp. were cultivated in bulk and biomasses used as biosorbents for the biosorption of an azo dye Orange G. Batch biosorption studies were performed for the removal of Orange G from aqueous solutions by varying the parameters like initial aqueous phase pH, biomass dosage, and initial dye concentration. It was found that the maximum biosorption was occurred at pH 2. Experimental data were analyzed by model equations such as Langmuir and Freundlich isotherms, and it was found that both the isotherm models best fitted the adsorption data. The monolayer saturation capacity was 0.48 mg/g for Aspergillus niger and 0.45 mg/g for Trichoderma sp. biomasses. The biosorption kinetic data were tested with pseudo first-order and pseudo second-order rate equations, and it was found that the pseudo second-order model fitted the data well for both the biomasses. The rate constant for the pseudo second-order model was found to be 10–0.8 (g/mg min⁻¹) for Aspergillus niger and 8–0.4 (g/mg min⁻¹) for Trichoderma sp. by varying the initial dye concentrations from 5 to 25 mg/l. It was found that the biomass obtained from Aspergillus niger was a better biosorbent for the biosorption of Orange G dye when compared to Trichoderma sp.     

Biosorption of nickel (II) from effluent of electroplating industry by immobilized cells of Bacillus species

In this study, Ni (II) biosorption capacity of immobilized cells of Bacillus sp. was investigated. Biosorption of Ni (II) was carried out in batch experiments and the important environmental conditions were optimized. The uptake of metal was rapid, and equilibrium was attained within 270 min. Bacillus strains (ten cultures) were isolated from nickel electroplating effluent by heat shock method. These isolates were grown up in nutrient broth supplemented with Ni (II)(50 mg/L). The culture, exhibiting maximum biosorption capacity (q^max: 118 mg/g), was selected and labeled Bacillus Bio‐4. In order to develop an economical biosorption process cell mass of Bacillus, Bio‐4 was immobilized in Na‐alginate. It was concluded from the results that biosorption of nickel is highly dependent on the type of sorbent and experimental conditions employed. Our results demonstrate that 6.0 mg immobilized cells (18 mg cell biomass in 3.0 mL of 1% Na alginate) had a maximum biosorption capacity of 113 mg Ni(II) per liter of suspension at pH 8.0, 100 rpm and 25°C. The Ni (II) removal was estimated to be 97.4%.