Response surface optimization of the removal of nickel from aqueous solution by cone biomass of Pinus sylvestris

Response surface methodology was applied to optimize the removal efficiency of Ni(II). Pinus sylvestris ovulate cones were used in this study. A 2(3) full-factorial central composite design was employed for experimental design and analysis of the results. The initial Ni(II) concentration (10-30 mg/l), pH (2.5-6.5) and biomass concentration (5-25 g/l) were the critical components of the removal optimized. The optimum pH, m (biomass concentration) and C0 (initial Ni(II) concentration) were found to be 6.17, 18.8 g/l and 11.175 mg/l, respectively. Under these conditions, removal efficiency of Ni(II) was 99.91%.     

Biosorption of aqueous chromium(VI) by Tamarindus indica seeds

The effectiveness of low cost agro-based materials namely, Tamarindus indica seed (TS), crushed coconut shell (CS), almond shell (AS), ground nut shell (GS) and walnut shell (WS) were evaluated for Cr(VI) removal. Batch test indicated that hexavalent chromium sorption capacity (q(e)) followed the sequence q(e)(TS) > q(e)(WS) > q(e)(AS) > q(e)(GS) > q(e)(CS). Due to high sorptive capacity, tamarind seed was selected for detailed sorption studies. Sorption kinetic data followed first order reversible kinetic fit model for all the sorbents. The equilibrium conditions were achieved within 150 min under the mixing conditions employed. Sorption equilibria exhibited better fit to Freundlich isotherms (R>0.92) than Langmuir isotherm (R approximately = 0.87). Hexavalent chromium sorption by TS decreased with increase in pH, and slightly reduced with increase in ionic strength. Cr(VI) removal by TS seems to be mainly by chemisorption. Desorption of Cr(VI) from Cr(VI) laden TS was quite less by distilled water and HCl. Whereas with NaOH, maximum desorption achieved was about 15.3%. When TS was used in downflow column mode, Cr(VI) removal was quite good but head loss increased as the run progressed and was stopped after 200 h.     

Biosorption of Cr (VI) from aqueous solution by Rhizopus nigricans

The study was aimed to quantify the Cr sorption ability of powdered biomass of Rhizopus nigricans at the best operating conditions. The influence of solution pH, agitation, Cr (VI) concentration, biomass dosage, contact time, biomass particle size and temperature were studied. The optimum pH for biosorption of Cr (VI) was found to be 2.0. Higher adsorption percentage was noted at lower initial concentrations of Cr ions, while the adsorption capacity of the biomass increased with increasing concentration of ions. Optimum biomass dosage was observed as 0.5% (w/v). More than 75% of the ions were removed within 30 min of contact and maximum removal was obtained after 8 h. Biomass particles of smaller size (90 microm) gave maximum adsorption (99.2%) at 100 mg/l concentration. The adsorption capacity increased with increase in temperature and agitation speed and the optimum were determined as 45 degrees C at 120 rpm. Freundlich and Langmuir isotherms were used to evaluate the data and the regression constants were derived. The adsorption rate constant values (Kad) were calculated for different initial concentration of Cr ions and the sorption was found to be higher at lower concentration (100 mg/l) of metal ion.     

Sorption of chromium(VI) from aqueous solution by cassava (Manihot sculenta Cranz.) waste biomass

The sorption of highly toxic Cr(VI) ions by cassava waste biomass was quantitatively investigated. The sorption was found to be influenced by several physico-chemical factors such as agitation speed, temperature, contact time, pH, and sorbent/sorbate ratio. The adsorption data at equilibrium were fitted to Freundlich and Langmuir isotherms. The monolayer sorption capacity was found to be 61.79 mg of Cr(VI) per gram of biomass. The kinetics of Cr(VI) adsorption to pure cassava-tuber-bark wastes were determined based on a pseudo-second-order-rate model using the batch-sorption technique at a temperature of 30 degrees. The kinetics data suggest that the adsorption process is exothermic, and that the rate-limiting step is physisorption. Negative DeltaG(ads) values indicate that the adsorption is spontaneous and exothermic in nature. Also, under optimal conditions (in agitated 1M H(2)SO(4) at 30 degrees), the cassava waste biomass appears to be recyclable.     

Biosorption of mercury from aqueous solution by Ulva lactuca biomass

The mercury biosorption onto non-living protonated biomass of Ulva lactuca, as an alternative method for mercury removal from aqueous solutions, was investigated. Batch equilibrium tests showed that at pH 3.5, 5.5 and 7 the maxima of mercury uptake values, according to Langmuir adsorption isotherm, were 27.24, 84.74 and 149.25 mg/g, respectively. The ability of Ulva lactuca biomass to adsorb mercury in fixed-bed column, was investigated as well. The influence of column bed height, flow rate and effluent initial concentration of metal was studied. The adsorbed metal ions were easily desorbed from the algal biomass with 0.3 N H₂SO₄ solution. After acid desorption and regeneration with distilled water, the biomass could be reused for other biosorption assays with similar performances.     

Biosorption of chromium(VI) by spent cyanobacterial biomass from a hydrogen fermentor using Box-Behnken model

The study explores utilization of waste cyanobacterial biomass of Nostoc linckia from a lab-scale hydrogen fermentor for the biosorption of Cr(VI) from aqueous solution. The biomass immobilized in alginate beads was used for removal of the metal in batch mode optimizing the process conditions adopting response surface methodology (RSM). Kinetic studies were done to get useful information on the rate of chromium adsorption onto the cyanobacterial biomass, which was found to follow pseudo second-order model. Four important process parameters including initial metal concentration (10-100 mg/L), pH (2-6), temperature (25-45 °C) and cyanobacterial dose (0.1-2.0 g) were optimized to obtain the best response of Cr(VI) removal using the statistical Box-Behnken design. The response surface data indicated maximum Cr(VI) biosorption at pH 2-4 with different initial concentrations of the metal in the aqueous solution. The biosorbent could remove 80-90% chromium from solutions with initial metal concentration of 10-55 mg/L. Involvement of the surface characteristics of the biomass was studied through its scanning electron micrographs and Fourier transform infrared (FTIR) analysis.     

Batch removal of chromium(VI) from aqueous solution by Turkish brown coals

The ability of using low-rank Turkish brown coals (Ilgın: BC₁, Beyşehir: BC₂, and Ermenek: BC₃) to remove Cr(VI) from aqueous solutions was studied as a function of contact time, solution pH, temperature, concentration of metal solutions and amount of adsorbent. Their sorption properties were compared with the activated carbon from Chemviron (AQ-30). Adsorption of Cr(VI) uptake is in all cases pH-dependent showing a maximum at equilibrium pH values between 2.0 and 3.2, depending on the biomaterial, that correspond to initial pH values of 2.3 units for BC₁, 3.0 units for BC₂ and 3.2 units for BC₃ and AQ-30. Batch equilibrium tests showed that the Cr(VI) removal was fitted with Freundlich isotherm and the adsorption reached equilibrium in 80 min. It was proceeding effectively into a short acid pH interval (2.0–3.2) where processes of Cr(VI) sorption are maximized. It was observed that the maximum adsorption capacity of 11.2 mM of Cr(VI)/g for Ilgın (BC₁), 12.4 mM of Cr(VI)/g for Beyşehir (BC₂), 7.4 mM of Cr(VI)/g for Ermenek (BC₃) and 6.8 mM of Cr(VI)/g for activated carbon (AQ-30) was achieved at pH of 3.0. The rise in temperature caused a slight decrease in the value of the equilibrium constant (K_c) for the sorption of Cr(VI) ion. The Cr(VI) sorption capacities of Beyşehir and Ilgın brown coals were the same. Ermenek brown coals and activated carbon (AQ-30) showed a similar sorption capacity.     

Biosorption of phenol from an aqueous solution by Aspergillus niger biomass

Intra-particle diffusion of sulfuric acid into sugarcane bagasse, corn stover, rice straw and yellow poplar was investigated to determine the effective diffusivity of sulfuric acid within the porous biomass structure. Diffusion experiments were conducted over 25-75 degrees C for two different biomass sizes using dynamic diffusion test cells. Diffusivities of sulfuric acid in agricultural residues were significantly higher than those of hard wood. Diffusivity data for each biomass were fitted into the Arrhenius equation for extrapolation to higher temperatures. The diffusivity data were subsequently incorporated into a theoretical model to determine acid profile within the biomass matrix. The modeling results indicate that intra-particle diffusion of acid influences the rate of dilute-acid pretreatment if unground biomass feedstock is used under normal pretreatment conditions. A criterion was set up to determine the critical biomass size at which the intra-particle acid diffusion becomes a rate-influencing factor for a given pretreatment condition.     

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.     

Biosorption of chromium(VI) in aqueous solutions by chemically modified Strychnine tree fruit shell

Chromium(VI) was removed from aqueous solution using sulfuric- and phosphoric-acid-activated Strychnine tree fruit shells (SSTFS and PSTFS) as biosorbents. Effects of various parameters such as adsorbent dose (0.02–0.1 g/L), temperature (303–333 K), agitation speed, solution pH (2–9), contact time, and initial Cr(VI) concentration (50–250 mg/L) were studied for a batch adsorption system. The optimum pH range for Cr(VI) adsorption was determined as 2. Equilibrium adsorption data were analyzed with isotherm models and the Langmuir and Freundlich models got best fitted values for SSTFS (R² value – 0.994) and PSTFS (R² value – 0.996), respectively. The maximum adsorption capacities of SSTFS and PSTFS were 100 and 142.85 mg/g, respectively. The biosorption process was well explained by pseudo-second-order kinetic model with higher R² value (SSTFS – 0.996, PSTFS – 0.990) for both biosorbents. Characterization of biosorbents was done using Fourier transform infrared spectroscopy, scanning electron microscopy, elemental analysis, energy-dispersive X-ray analysis, and thermogravimetric analysis. Thermodynamic studies revealed the spontaneous, endothermic, and randomness in nature of the Cr(VI) adsorption process. Different concentrations of NaOH solutions were used to perform the desorption studies. The results demonstrated that both SSTFS and PSTFS can be used as an effective and low-cost biosorbent for removal of Cr(VI) from aqueous solutions.     

Biosorption of Pb(II) and Cr(III) from aqueous solution by lichen (Parmelina tiliaceae) biomass

The biosorption characteristics of Pb(II) and Cr(III) ions from aqueous solution using the lichen (Parmelina tiliaceae) biomass were investigated. Optimum biosorption conditions were determined as a function of pH, biomass dosage, contact time, and temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm of the metal ions by P. tiliaceae biomass. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The monolayer biosorption capacity of P. tiliaceae biomass for Pb(II) and Cr(III) ions was found to be 75.8 mg/g and 52.1mg/g, respectively. From the D-R isotherm model, the mean free energy was calculated as 12.7 kJ/mol for Pb(II) biosorption and 10.5 kJ/mol for Cr(III) biosorption, indicating that the biosorption of both metal ions was taken place by chemical ion-exchange. The calculated thermodynamic parameters (delta G degrees , delta H degrees and delta S degrees ) showed that the biosorption of Pb(II) and Cr(III) ions onto P. tiliaceae biomass was feasible, spontaneous and exothermic under examined conditions. Experimental data were also tested in terms of biosorption kinetics using pseudo-first-order and pseudo-second-order kinetic models. The results showed that the biosorption processes of both metal ions followed well pseudo-second-order kinetics.     

Biosorption of iron(III) from aqueous solution by dried biomass of Synechocystis sp. PCC 6803

Journal of Applied Phycology - In this study, the dried biomass of Synechocystis sp. PCC 6803 was used as biosorbent for removing Fe(III)) ions from aqueous solution. The effects of exposure time,...     

Continuous removal of Cr(VI) from aqueous solution catalysed by palladised biomass of Desulfovibrio vulgaris

Growth-decoupled cells of Desulfovibrio vulgaris NCIMB 8303 can be used to reduce Pd(II) to cell-bound Pd(0) (Bio-Pd(0)), a bioinorganic catalyst capable of reducing hexavalent chromium to less toxic Cr(III), using formate as the electron donor. Magnetic resonance imaging showed that Bio-Pd(0), immobilized in chitosan and agar beads, is distinguishable from the surrounding gel and is evenly dispersed within the immobilization matrix. Agar-immobilized Bio-Pd(0) and 'chemical Pd(0)' were packed into continuous-flow reactors, and challenged with a solution containing 100 microM Cr(VI) (pH 7) at a flow rate of 2.4 ml h(-1). Agar-immobilized chemical Pd(0) columns lost Cr(VI) reducing ability by 160 h, whereas columns containing immobilized Bio-Pd(0) maintained 90% reduction until 680 h, after which reduction efficiency was gradually lost.     

Biosorption of a reactive dye (Rhodamine-B) from an aqueous solution using dried biomass of activated sludge

Low cost, locally available biomaterial was tested for its ability to remove reactive dyes from aqueous solution. Granules prepared from dried activated sludge (DAS) were utilized as a sorbent for the uptake of Rhodamine-B (Rh-B) dye. The effects of various experimental parameters (dye concentration, sludge concentrations, swelling, pretreatment and other factors) were investigated and optimal experimental conditions were ascertained. Nearly 15min was required for the equilibrium adsorption, and Rh-B dyes could be removed effectively. Dye removal performance of Rh-B and DAS increased with increasing concentrations. The acid pretreated biomass exhibited a slightly better biosorption capacity than alkali pretreated or non-pretreated biomass. The optimum swelling time for dye adsorption of the DAS within the swelling time range studied was 12h. Both the Freundlich and Langmuir isotherm models could describe the adsorption equilibrium of the reactive dye onto the activated sludge with the Langmuir isotherm showing the better agreement of the two. Second-order kinetic models confirmed the agreement.     

Mechanism of reduction of chromium(VI) ion by 2-mercaptosuccinic acid in aqueous solution

The kinetics of the reduction of the chromium(VI) ion by 2-mercaptosuccinic acid (thiomalic acid) were studied by rapid scanning stopped flow spectrophotometry. The conditions used were [Cr(VI)]_T=0.20 mM, [MSA]_T=5-90 mM, 3.0≤pH≤5.6 in citric acid-phosphate buffer, or 3.3≤pH≤5.4 in 0.40 M acetic acid-acetate buffer, 20.0≤T≤35.0 °C at I=0.50 M (NaClO₄). Spectrophotometric titration at 350 nm indicates the stoichiometry of the reaction to be 1:3. The kinetics of both formation and decay of the intermediate chromium(VI) thioester were followed at λ_max=425 nm and rate expressions, specific rate constants and corresponding activation parameters were derived from the proposed mechanism. The acetic acid-acetate buffer was found to catalyze the formation but not the decay rate of the intermediate. The citric acid-phosphate buffer and dissolved oxygen did not have any significant effect on the reaction rates. The justification of the mechanism was discussed in terms of standard biological conditions.     

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.     

Adsorption of chromium (VI) ion from aqueous solution by succinylated mercerized cellulose functionalized with quaternary ammonium groups

Succinylated mercerized cellulose (cell 1) was used to synthesize an anion exchange resin. Cell 1, containing carboxylic acid groups was reacted with triethylenetetramine to introduce amine functionality to this material to obtain cell 2. Cell 2 was reacted with methyl-iodide to quaternize the amine groups from this material to obtain cell 3. Cells 2 and 3 were characterized by mass percent gain, degree of amination and quaternization, FTIR and CHN. Cells 2 and 3 showed degrees of amination and quaternization of 2.8 and 0.9 mmol/g and nitrogen content of 6.07% and 2.13%, respectively. Cell 3 was used for Cr (VI) adsorption studies. Adsorption equilibrium time and optimum pH for Cr (VI) adsorption were found to be 300 min and 3.1, respectively. The Langmuir isotherm was used to model adsorption equilibrium data. The adsorption capacity of cell 3 was found to be 0.829 mmol/g. Kinetic studies showed that the rate of adsorption of Cr (VI) on cell 3 obeyed a pseudo-second-order kinetic model.     

Biosorption of Pb2+ from aqueous solution by waste biomass of aerial roots of Rhizophora mangle (red mangrove)

The processing waste of the aerial roots of Rhizophora mangle was used in both its unmodified or mercaptoacetic acid (MAA) modified form for the sorption of Pb2+ from aqueous solution. The biomass rapidly and strongly sorbed Pb2+ at pH 5.0, which indicated chemisorption. A significant increase in Pb2+ sorption resulted from MAA treatment of the biomass, indicating that sorption occurs through an ion-exchange process. From sorption-capacity experiments, the unmodified and modified materials extracted, at pH 5, 31.3 and 85.5 mg of Pb2+ per gram of biomass, respectively, from aqueous solutions. Our studies may contribute to an innovative method for the economical and ecologically save removal and recovery of heavy-atom metal ions from contaminated waters through biosorption.     

Biosorption of pentachlorophenol from aqueous solutions by a fungal biomass

This study focuses on the use of non-viable Aspergillus niger biomass, for the biosorption of pentachlorophenol (PCP) from aqueous solutions. Various forms of the biomass-autoclaved and chemically conditioned, were tested for their potential in the removal of PCP from aqueous solutions. It was found that PCP removal was pH dependent; PCP removal decreased with the increase in pH for all type of biomass, except for cetyltrimethylammonium bromide (CTAB) biomass. For CTAB biomass, a near complete removal of PCP was observed at all pHs. Therefore, CTAB biomass was used in further studies. PCP removal was rapid, with an equilibrium time of 2h. The rate of adsorption kinetics was well described by a pseudo-second order model. Isotherm models of the type one and two parameter models were found to fit the isotherm data. PCP biosorption was found to be exothermic in nature; the amount of PCP sorbed decreased with an increase in temperature. Desorption was carried out using deionized water, dilute HCl and dilute NaOH, and it was found that most of the PCP was irreversibly bound to the biomass. The addition of inorganic salts did not affect the removal of PCP from aqueous solutions. Among the surface functional groups present on the biomass, carboxyl, amide and hydroxyl groups seem to have played a role in PCP biosorption. It was concluded that CTAB treated biomass was an excellent adsorbent for the removal of PCP from aqueous solutions.