Heavy metal biosorption by biomass of Ochrobactrum anthropi producing exopolysaccharide in activated sludge

The removal of chromium, cadmium and copper, toxic metals of high environmental priority due to their toxicity, from dilute aqueous solutions has been studied in the present work, applying a dead exopolysaccharide producing bacterium, Ochrobactrum anthropi, isolated from activated sludge. Particularly, the effect of pH, metal concentration and the effects of contact time were considered. Optimum adsorption pH values of chromium(VI), cadmium(II) and copper(II) were 2.0, 8.0 and 3.0 respectively. Experimental results also showed the influence of initial metal concentration on the metal uptake for dried biomass. Both the Freundlich and Langmuir adsorption models were suitable for describing the short-term biosorption of chromium(VI), cadmium(II) and copper(II) by O. anthropi.     

A comparative study on heavy metal biosorption characteristics of some algae

The biosorption of copper(II), nickel(II) and chromium(VI) from aqueous solutions on dried (Chlorella vulgaris, Scenedesmus obliquus and Synechocystis sp.) algae were tested under laboratory conditions as a function of pH, initial metal ion and biomass concentrations. Optimum adsorption pH values of copper(II), nickel(II) and chromium(VI) were determined as 5.0, 4.5 and 2.0. respectively, for all three algae. At the optimal conditions, metal ion uptake increased with initial metal ion concentration up to 250 mg l⁻¹. Experimental results also showed the influence of the alga concentration on the metal uptake for all the species. Both the Freundlich and Langmuir adsorption models were suitable for describing the short-term biosorption of copper(II), nickel(II) and chromium(VI) by all the algal species.     

Biosorption of iron(III)–cyanide complex anions to Rhizopus arrhizus: application of adsorption isotherms

The biosorption of iron(III)–cyanide complex anions to Rhizopus arrhizus was investigated. The iron(III)–cyanide complex ion binding capacity of the biosorbent was a function of initial pH, initial iron(III)–cyanide complex ion and biosorbent concentration. These results indicated that a significant reduction of iron(III)–cyanide complex ions was achieved at pH 13, a highly alkaline condition. The maximum loading capacity of biosorbent was 612·2 mg g⁻¹ at 1996·2 mg litre⁻¹ initial iron(III)–cyanide complex ion concentration at this pH. The Freundlich, Langmuir and Redlich–Peterson adsorption models were fitted to the equilibrium data at pH 3·0, 7·0 and 13·0. The equilibrium data could be best fitted to by all the adsorption models over the entire concentration range (50–2000 mg litre⁻¹) at pH 13.     

Potential use of green algae as a biosorbent for hexavalent chromium removal from aqueous solutions

The hexavalent chromium Cr(VI) poses a threat as a hazardous metal and its removal from aquatic environments through biosorption has gained attention as a viable technology of bioremediation. We evaluated the potential use of three green algae (Cladophora glomerata, Enteromorpha intestinalis and Microspora amoena) dry biomass as a biosorbent to remove Cr(VI) from aqueous solutions. The adsorption capacity of the biomass was determined using batch experiments. The adsorption capacity appeared to depend on the pH. The optimum pH with the acid-treated biomass for Cr(VI) biosorption was found to be 2.0 at a constant temperature, 45?°C. Among the three genera studied, C. glomerata recorded a maximum of 66.6% removal from the batch process using 1.0?g dried algal cells/100?ml aqueous solution containing an initial concentration of 20?mg/L chromium at 45?°C and pH 2.0 for 60?min of contact time. Langmuir and Freundlich isotherm equations fitted to the equilibrium data, Freundlich was the better model. Our study showed that C. glomerata dry biomass is a suitable candidate to remove Cr(VI) from aqueous solutions.     

Biosorption of reactive dyes by dried activated sludge: equilibrium and kinetic modelling

The biosorption of reactive dyes (Reactive Blue 2 - RB2 and Reactive Yellow 2 - RY2) onto dried activated sludge was investigated. The dye binding capacity of biosorbent was shown as a function of initial pH, initial dye concentration and type of dye. The equilibrium data fitted very well to both the Freundlich and Langmuir adsorption models. The results showed that both the dyes uptake processes followed the second-order rate expression.     

Biosorption of chromium(VI) from aqueous solution by cone biomass of Pinus sylvestris

Biosorption of chromium(VI) on to cone biomass of Pinus sylvestris was studied with variation in the parameters of pH, initial metal ion concentration and agitation speed. The biosorption of Cr(VI) was increased when pH of the solution was decreased from 7.0 to 1.0. The maximum chromium biosorption occurred at 150 rpm agitation. An increase in chromium/biomass ratio caused a decrease in the biosorption efficiency. The adsorption constants were found from the Freundlich isotherm at 25 degrees C. The cone biomass, which is a readily available biosorbent, was found suitable for removing chromium from aqueous solution.     

Nickel Removal from Aqueous Solutions Using Sheep Manure Wastes

This paper reports a study on the potential use of sheep manure waste (SMW) for the removal of nickel ions from aqueous solutions. The adsorption of nickel ions from aqueous solutions on SMW has been studied as functions of contact time, initial pH, amount of sorbent, sorbent particle size, initial concentration of nickel ions, salt, and chelating agents. The experimental results showed that the SMW has a high affinity for nickel binding, where 79 % removal of 100 ppm initial nickel ions concentration was obtained using 8.0 mg SMW/mL, at pH 6.5 in 4 minutes equilibrium time. The equilibrium adsorption data were analyzed using four different isotherms: the Langmuir, Freundlich, Redlich‐Peterson, and Sips isotherm equations. The results of the kinetic studies showed that the adsorption of nickel ions on SMW is a pseudo‐first order with respect to the nickel ions solution concentration.     

Modeling studies on mono and binary component biosorption of phenol and cyanide from aqueous solution onto activated carbon derived from saw dust

Biosorption is an effective treatment method for the removal of phenol and cyanide from aqueous solution by saw dust activated carbon (SDAC). Batch experiments were achieved as a function of several experimental parameters, i.e. influence of biosorbent dose (5–60 g/L) contact time (2–40 h), pH (4–12), initial phenol concentration (100–1000 mg/L) and initial cyanide concentration (10–100 mg/L) and temperature (20–40 °C). The biosorption capacities of the biosorbent were detected as 178.85 mg/g for phenol with 300 mg/L of initial concentration and 0.82 mg/g for cyanide with 30 mg/L of initial concentration. The optimum pH is found to be 8 for phenol and 9 for cyanide biosorption. The mono component biosorption equilibrium data for both phenol and cyanide were well defined by Redlich–Peterson model and binary component adsorption equilibrium data well fitted by extended Freundlich model. The percentage removal of phenol and cyanide using SDAC was 66.67% and 73.33%, respectively. Equilibrium established within 30 h for phenol and 28 h for cyanide. Kinetic studies revealed that biosorption of phenol followed pseudo second order indicating adsorption through chemisorption and cyanide followed pseudo first order kinetic model indicating adsorption through physisorption. Thermodynamic studies parameters, i.e., enthalpy (Δh₀), entropy (ΔS₀) and Gibb’s free energy (ΔG₀) have also been considered for the system. Thermodynamic modeling studies revealed that the process of cyanide biosorption was endothermic and phenol biosorption was exothermic in nature.     

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.     

Application of Freundlich and Langmuir models to multistage purification process to remove heavy metal ions by using Schizomeris leibleinii

The adsorption of iron(III), lead(II) and cadmium(II) ions onto Schizomeris leibleinii, a green alga, was studied with respect to initial pH, temperature, initial metal ion and biomass concentration to determine the optimum adsorption conditions. Optimum initial pH for iron(III), lead(II) and cadmium(II) ions were 2.5, 4.5 and 5.0 at optimum temperature 30°C, respectively. The initial adsorption rates increased with increasing initial iron(III), lead(II) and cadmium(II) ion concentrations up to 100, 100 and 150 mg l⁻¹, respectively. The Freundlich and Langmuir adsorption isotherms were developed at various initial pH and temperature values. The adsorption of these metal ions to S. leibleinii was investigated in a two-stage mixed batch reactor. The residual metal ion concentrations (C_eq) at equilibrium at each stage for a given ‘quantity of dried algae (X₀)/volume of solution containing heavy metal ion (V₀)’ ratio were calculated using Freundlich and Langmuir isotherm constants. The experimental biosorption equilibrium data for iron(III), lead(II) and cadmium(II) ions were in good agreement with those calculated by both Freundlich and Langmuir models. The adsorbed iron(III), lead(II) and cadmium(II) ion concentrations increased with increasing X₀/V₀ ratios while the adsorbed metal quantities per unit mass of dried algae decreased.     

Removal of hexavalent chromium by fungal biomass of <Emphasis Type="Italic">Mucor racemosus</Emphasis>: influencing factors and removal mechanism

This study reported the hexavalent chromium removal by untreated Mucor racemosus biomass and the possible mechanism of Cr (VI) removal to the biomass. The optimum pH, biomass dose, initial Cr (VI) concentration and contact time were investigated thoroughly to optimize the removal condition. The metal removal by the biomass was strongly affected by pH and the optimum pH ranged from 0.5 to 1.0. The residual total Cr was determined. It was found that dichromate reduction occurred at a low very low pH value. At biomass dose 6 g/l, almost all the Cr (VI) ions were removed in the optimum condition. Higher removal percentage was observed at lower initial concentrations of Cr (VI) ions, while the removal capacity of the biomass linearly depended on the initial Cr (VI) concentration. More than half of Cr (VI) ions were diminished within 1 h of contact and removal process reached a relative equilibrium in approximately 8 h. Almost all of the Cr (VI) ions were removed in 24 h when initial concentrations were below 100 mg/l. The equilibrium data were fitted in to the Langmuir and the Freundlich isotherm models and the correlated coefficients were gained from the models. A Fourier transform infrared spectra was employed to elucidate clearly the possible biosorption mechanism as well.     

Removal of hexavalent chromium using distillery sludge

Batch mode experiments were conducted to study the removal of hexavalent chromium from aqueous and industrial effluent using distillery sludge. Effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(VI) were studied. The data obeyed Langmuir and Freundlich adsorption isotherms. The Langmuir adsorption capacity was found to be 5.7 mg/g. Freundlich constants K(f) and n were 2.05 [mg/g(L/mg)(n)] and 3.9, respectively. Desorption studies indicated the removal of 82% of the hexavalent chromium. The efficiency of adsorbent towards the removal of chromium was also tested using chromium-plating wastewater.     

Biosorption of hexavalent chromium from aqueous solution by a tropical basidiomycete BDT-14 (DSM 15396)

Summary A tropical white-rot basidiomycete, BDT-14 (DSM 15396) was investigated for its chromium (VI) biosorption potential from an aqueous solution. Pre-treatment of fungal biomass with acid resulted in 100% metal adsorption compared to only 26.64% adsorption without any pre-treatment. Chromium adsorption was a rapid process at early exposure resulting in 60% chromium removal within the first 2 h of exposure. An increase in biomass showed an increase in the total metal ions adsorption but a decrease in specific uptake of metal ions. The concentrations of chromium had a pronounced effect on the rate of adsorption. The adsorption efficiency was 100% when the initial Cr (VI) concentration was 100 mg l⁻¹ with 1,000 mg biomass. Only 47.5% adsorption was observed with 500 mg l⁻¹ Cr (VI) concentration. The adsorption data fit well with the Langmuir and Freundlich isotherm models. Comprehensive characterization of parameters indicates BDT−14 biomass as a promising material for Cr (VI) adsorption.     

Kinetic and Equilibrium Studies of Cr(VI) Biosorption by Dead <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> Biomass

Many studies have been carried out on the biosorption capacity of different kinds of biomass. However, reports on the kinetic and equilibrium study of the biosorption process are limited. In our experiments, the removal of Cr(VI) from aqueous solution was investigated in a batch system by sorption on the dead cells of Bacillus licheniformis isolated from metal-polluted soils. Equilibrium and kinetic experiments were performed at various initial metal concentrations, pH, contact time, and temperatures. The biomass exhibited the highest Cr(VI) uptake capacity at 50°C, pH 2.5 and with the initial Cr(VI) concentration of 300 mg/g. The Langmuir and Freundlich models were considered to identify the isotherm that could better describe the equilibrium adsorption of Cr(VI) onto biomass. The Langmuir model fitted our experimental data better than the Freundlich model. The suitability of the pseudo first-order and pseudo second-order kinetic models for the sorption of Cr(VI) onto Bacillus licheniformis was also discussed. It is better to apply the pseudo second-kinetic model to describe the sorption system.     

Chromate (VI) uptake by and interactions with cyanobacteria

Summary The short-term accumulation of chromate by the cyanobacteriaAnabaena variabilis andSynechococcus PCC 6301 has been described as consisting of a rapid and relatively low level of biosorption of chromate to the cell walls; no energy-dependent uptake was detected. This biosorption was dependent on chromate concentration and could be described by a Freundlich adsorption isotherm for both cyanobacterial species studied. Decreasing the external pH increased the chromate accumulation by both species. Over a longer time period with growth it was shown thatA. variabilis was capable of reducing chromate (VI) to chromium (III) and then accumulating the chromium (III).Synechococcus PCC 6301 showed no further interaction with chromate concentrations over the same time period after the initial biosorption.     

Kinetic and equilibrium models for biosorption of Cr(VI) on chemically modified seaweed,Cystoseira indica

The biosorption data of hexavalent chromium by marine brown algae Cystoseira indica, which was chemically modified by crosslinking with epichlorohydrin (CB1, CB2), or oxidized by potassium permanganate (CB3), or only washed with distilled water (RB), has been used for kinetic studies based on fractional power, Elovich, pseudo-first order and pseudo-second order rate expressions. Five three parameter biosorption isotherm models, viz. Redlich–Peterson, Sips, Khan, Radke–Prausnitz and Toth are tested for their applicability apart from 6 two-parameter models. Non-linear curve fitting procedure was adopted for fitting the kinetic as well as equilibrium data in the kinetic and isotherm models and for the determination of parameters. The time-dependent Cr(VI) biosorption data were well-described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that film diffusion might be involved in Cr(VI) biosorption in the present case. Among the two-parameter models, the Langmuir model produces the best fit, while, among the three-parameter models, the best fit is produced by the Khan model, for the biosorption of Cr(VI) on all the four biosorbents studied.     

Biosorption of Pb(II) and Cu(II) by activated sludge in batch and continuous-flow stirred reactors

Biosorption of Pb(II) and Cu(II) ions in single component and binary systems was studied using activated sludge in batch and continuous-flow stirred reactors. In biosorption experiments, the activated sludge in three different phases of the growth period was used: growing cells; resting cells; dead or dried cells. Because of the low adsorption capacity of the non-viable activated sludge especially in the case of Pb(II) ions, biosorption of the Cu(II) and Pb(II) ions from the binary mixtures was carried out by using the resting cells. The biosorption data fitted better with the Freundlich adsorption isotherm model. Using a mathematical model based on continuous system mass balance for the liquid phase and batch system mass balance for the solid phase, the forward rate constants for biosorption of Pb(II) and Cu(II) ions were 0.793 and 0.242 1 (mmolmin)(-1), respectively.     

Biosorption of Cr (VI) with Trichoderma viride immobilized fungal biomass and cell free Ca-alginate beads

Ability of Cr (VI) biosorption with immobilized Trichoderma viride biomass and cell free Ca-alginate beads was studied in the present study. Biosorption efficiency in the powdered fungal biomass entrapped in polymeric matric of calcium alginate compared with cell free calcium alginate beads. Effect of pH, initial metal ion concentration, time and biomass dose on the Cr (VI) removal by immobilized and cell free Ca-alginate beads were also determined. Biosorption of Cr (VI) was pH dependent and the maximum adsorption was observed at pH 2.0. The adsorption equilibrium was reached in 90 min. The maximum adsorption capacity of 16.075 mgg(-1) was observed at dose 0.2 mg in 100 ml of Cr (VI) solution. The high value of kinetics rate constant Kad (3.73 x 10(-2)) with immobilized fungal biomass and (3.75 x 10(-2)) with cell free Ca- alginate beads showed that the sorption of Cr (VI) ions on immobilized biomass and cell free Ca-alginate beads followed pseudo first order kinetics. The experimental results were fitted satisfactory to the Langmuir and Freundlich isotherm models. The hydroxyl (-OH) and amino (-NH) functional groups were responsible in biosorption of Cr (VI) with fungal biomass spp. Trichoderma viride analysed using Fourier Transform Infrared (FTIR) Spectrometer.     

Bioaccumulation and biosorption of chromium by Aspergillus niger MTCC 2594

Chromium toxicity is of prime concern due to chrome tanning processes in the leather sector. Chrome tanning results in the discharge of toxic levels of chromium causing pollution hazards. Chromium levels of Cr(III) and Cr(VI) were high above permissible limits in chrome samples after chrome tanning. The potential of Aspergillus niger MTCC 2594 to accumulate chromium as well as its biosorption capacity is investigated in this study. Bioaccumulation of Cr(III) and Cr(VI) in the spent chrome liquor has resulted in a 75-78% reduction of the initial Cr content in 24-36 h. A. niger biomass is found to be very effective in the biosorption of Cr(III) and Cr(VI) in spent chrome liquor. Maximum adsorption of 83% for biosorption of Cr(III) at 48 h and 79% of Cr(VI) at 36 h in spent chrome liquor is observed. The biosorption characteristics fit well with Langmuir and Freundlich isotherms and the adsorption parameters are evaluated. The biosorption of Cr also follows Lagergren kinetics. A. niger biomass is effectively used for the biosorption of chromium with 79-83% Cr removal in 36-48 h.     

Removal of Chromium(VI) Ions from Synthetic Solutions by the Fungus Penicillium purpurogenum

The ability of Penicillium purpurogenum to bind high amounts of chromium(VI) from aqueous solutions is demonstrated. Cr(VI) adsorption capacity increases with time during the first four hours and then leveled off toward the equilibrium adsorption capacity. Biosorption of Cr(VI) ions reached equilibrium in four hours. Binding of Cr(VI) ions with Penicillium purpurogenum biomass was clearly pH dependent. Cr(VI) loading capacity increased with increasing pH. The adsorption of Cr(VI) ions reached a plateau value at a pH of approx. 6.0. The maximum capacity of adsorption of Cr(VI) ions onto the fungal biomass was 36.5 mg/g. Adsorption behavior of Cr(VI) ions can be approximately described with the Langmuir equation. When applying the Langmuir model, the maximum adsorption capacity (Q_max) and the Langmuir constant were found to be 40 mg/g and 3.9 × 10^–3 mg/L. Elution of Cr(VI) ions was performed by means of 0.5 M HCl. It was possible to use the biomass of Penicillium purpurogenum for six cycles for biosorption.