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The biomass of white rot basidiomycete, Lentinus strigosus had the ability to adsorption of reactive dyes from aqueous solution.
Current, synthetic dyes are used in a variety of industries such as textile, paper, printing, pharmaceutical, leather, food and cosmetics (à¸à¹‰à¸²à¸‡à¸à¸´à¸‡à¸ˆà¸²à¸ thesis à¹€à¸£à¸·à¹ˆà¸à¸‡à¸ªà¸µà¸¢à¹‰à¸à¸¡) The biomass of white rot basidiomycete, Lentinus strigosus had the ability to adsorption of reactive dyes from aqueous solution.
2. Material and methods
Three dyes were used studied include Remazol Brilliant Blue R (RBBR) and Remazol Black B (RB5) were obtained from Dystar Thai Company Limited in Thailand. Stock solution were prepared in distilled water by diluting 1.0 g l-1 of each dyes
2.2. Fungal stain, media and culture condition
Lentinus strigosus was obtained from Department of Agriculture, Ministry of Agriculture and Cooperative in Thailand. Stock culture was maintained on Potato Dextrose Agar (PDA) at 4°C until use. The preparation of mycelium was grown on fresh PDA and incubated at room temperature (28 - 30 °C). To preparation of fungal biomass in 100 ml Potato Dextrose Broth (PDB) with 10 agar plugs (Ø5 mm from the edge of a 5-day-old agar culture) of Lentinus strigosus and incubated at room temperature (28 - 30 °C). After 7 days of cultivation , they were harvested and washed three times with distilled water for used as living biomass. White dead biomass through autoclaved at 121 °C and 1 atm for 20 min. This was ready to be used for further experiments.
Fig. 1. Chemical structure: (a) Remazol Brilliant Blue R (RBBR); (b) Remazol Black B (RB5)
2.3. Biosorption and kinetics studies
The 100 ml of 50 mg l-1 each dyes solution contained with 1 g wet weight of living or dead fungal biomass in 250 ml Elermyer flask. The mixtures solution were incubated at 30 °C and shaking on rotary shaker at 150 rpm for 6 h to ensure equilibrium. The biomass removed from the dyes solution by centrifugation at 5000 rpm for 5 min. Residual concentration of dyes was determined spectrophotometerically (Jusco V-530 UV/VIS spectrophotometer) at 592 and 597 for RBBR and RB5 respectively. The effect of pH on dyes adsorption was determined with adjust the mixtures at pH values from 2 - 8 with 1 M NaOH or HCl. The effect of temperature was incubated under different temperature range between 20 - 60 °C with 10 °C increment. The effect of contact time on biomass adsorption determined was incubated the mixtures for 15 - 360 min. The effect of initial dyes concentration determined was tested using 50 - 1000 mg l-1 each dyes solution. The experiments were performed in triplicate for each mixture.
2.4 Adsorption isotherms
The amount of dyes adsorbed per unit living or dead biomass (mg dyes/g biomass biosorbent) was determined using the following expression (1)
qeq = (1)
where qeq is the dyes uptake (mg dyes/g biomass weight of living or dead biomass); V is the volume of dyes solution (ml); Ci is the initial concentration of dyes in the solution (mg l-1); C is the residual concentration of in the solution at any time and M is the biomass weight of living or dead biomass.
The studied efficiency of adsorption were used Langmuir and Freundlich isotherm models(à¸à¹‰à¸²à¸‡à¸à¸´à¸‡à¸ˆà¸²à¸ Kinetic and equilibrium syudies on the biosorption of reactive black 5 dye by Aspergillus foetidus à¹à¸¥° Biosorption of reactive red-120 dye from aqueous solution by native and modified fungus biomass preparations of Lentinus sajor-caju) for the evalution of the adsorption data. The Langmuir isotherm is based on the homogeneous surface and monolayer adsorption, and is presented by the following equation (2)
where qeq and qmax are the equilibrium and maximum uptake capacities (mg g-1 biosorpbent); Ceq is the equilibrium concentration (mg l-1 solution); b is the equilibrium constant (l mg-1)
The Freundlich isotherm model is base on heterogeneous surface and multilayer adsorption, and is presented by the following equation (3)
where KF and n are the Freundlich contants characteristic of the system.
The pseudo-first-order Largergren and the pseudo-second order biosorption process (à¸à¹‰à¸²à¸‡à¸à¸´à¸‡à¸ˆà¸²à¸ Biosorption of bromophenol blue from aqueous solutions by rhizopus stolonifer biomass>>>> à¹€à¸›à¸´à¸”à¹„à¸›à¸”à¸¹à¸‚à¹‰à¸²à¸‡à¸«à¸¥à¸±à¸‡ ref à¹à¸¥à¹‰à¸§à¸™à¸³à¸¡à¸²à¸à¹‰à¸²à¸‡à¸à¸µà¸-à¸µ) were applied to experimental data.
The first-order rate expression of Largergren is showed as following equation (4)
log(qeq - q) = logqeq - k1,adt/2.303 (4)
where q is the amount of adsorbed dye on the biosorbent at time t, and k1,adt is the rate constant to Largergren first-order biosorption.
The pseudo second-order kinetic rate equation is showed as following equation (5)
t/q = 1/(k2,adq2eq) + t/qeq (5)
where k2,ad is the rate contant of second-order biosorption.
The pseudo first-order condiders the rate of occupation of adsorption sites to be proportional to the number of uncupation sites. A straight line of log (qe -qt) versus t indicates. In a true first-order process log q should by equal to the intercept of a plot of log (qe -qt) against t. The second-order reaction rate equilibrium constant. A plot of t/qeq versus t should give a linear relationship for the applicability of the second-order kinetic.
3. Resut and discussion
3.1. Effect of the pH on the Biosorption Capacity
The pH is an important parameter for the biosorption process. It will affect the between ionization status of the dyes molecule and the surface of fungal biomass in solution (à¸à¹‰à¸²à¸‡à¸à¸´à¸‡à¸ˆà¸²à¸ Immobilization of trichoderma viride for enhanced methylene blue biosorption: Batch and column studies à¹à¸¥° Biosorption of reactive dye by loofa sponge-immobilized funfal biomass of Phanerochaete chrysosporium).Therefore, the effect of pH on dyes adsorption was investigated at 2.0 - 8.0. Fig. 2 showed that the effect of pH on dye biosorption uptake using live and dead biomass. The maximum biosorption of RBBR and RB5 was found as 46.01 ± 0.39 and 43.70 ± 2.01 mg g-1 for live fungal biomass and 44.36 ± 0.37 and 49.25 ± 0.08 mg g-1 for dead fungal biomass at pH 2.0 and significantly decreased by increasing the pH values.
Fig. 2. Effect of the pH on the biosorption capacity by biomass of L. strigosus. 50 mg l-1 dyes; T = 30 °C; 150 rpm; 6 h.
When considering the structure of the dyes were RBBR and RB5 (Fig. 1) are sulfonate group in the molecular structure, which have negative charges in aqueous solution. While the acidic condition, the fungal biomass will have a net positive charge due to protonation of functional group on cell wall such as amine, carboxyl, hydroxyl, sulphates and phosphates was responsible for interacting with the dyes molecule (à¸à¹‰à¸²à¸‡à¸à¸´à¸‡à¸ˆà¸²à¸ Biosorption of chromium by teritomyces clypeatus à¹à¸¥° A comparision study on biosroption characteristics of certain fungi for bromophenol blue dye.). When comparing physical characterstics of the fungal biomass was found that the dead biomass that can adsorped of the RBBR and RB5 better than the live biomass, may be the dead biomass can suffer rupture, and denateration of the cell wall can allow free access to cell wall binding sites. (à¸à¹‰à¸²à¸‡à¸à¸´à¸‡à¸ˆà¸²à¸ Two and three-parameter isothermal modeling for liquid-phase sorption of procion Blue H-B by inactive mycelia biomass of Panus fulvus) According to O'Mahony et al. (à¸à¹‰à¸²à¸‡à¸à¸´à¸‡à¸ˆà¸²à¸ Reactive dye biosorption by Rhizopus arrhizus biomass) reported using that Rhizaous arrhizus biomass for biosorption of reactive dyes and the maximum dyes biosorption was at pH 2.0.
3.2 Effect of Time on the Biosorption capacity
The effect of temperature on the biosorption of RBBR and RB5 by live and dead fungi biomass at equilibrium was investigated at the temperature range between 20 - 60 °C with 10 °C increment, at the initial dyes concentration of 50 mg l-1, pH 2.0 (Fig. 3.) In the case of adsorption for RBBR and RB5 by live fungi biomass was noted to enhance to increase with the increase in temperature up to 60 °C was found that . When considering in the case of adsorption the dyes by dead fungal biomass was noted to decease with the further increase in temperature.
Fig. 3. Effect of temperature on the equilibrium sorption capacity of live and dead fungal biomass for RBBR and RB5 from 100 mg l-1 dyes solution at pH 2.0, was mixed with each biosorbent at 150 rpm on rotary shaker