Biosorption process

Biosorption is a general phenomenon that can occur in either dead or living biomass. However, this process usually refers to a passive uptake mechanism carried out by nonviable microorganisms (dead yeasts). The biosorption process involves physical-chemical interactions between the yeast surface and the azo dyes, as well as possible passive diffusion inside dead cells. 

Metal ion binding during biosorption processes has been found to involve a complex mechanism, such as ion-exchange, complexation, electrostatic attraction or micro precipitation. 

Various metal-binding mechanisms have been postulated to be active in biosorption process and presented in Figure 3.2. 

Seed kernels of M. oleifera are known to remove lead, iron and cadmium ions from contaminated water by a biosorption process through the metal -protein interactions(2d,5i/ M. oleifera pods (MOP) shows sorption potential for the removal of organics (e.g. benzene, toluene, ethylbenzene and cumene (BTEC)) from aqueous media and methyl parathion pesticide (MP) from surface and ground waters (68,69). M. oleifera alone or in combination can effectively be used and replace alum for dewatering of chemical sludge. In comparison to alum, M. oleifera shows comparable conditioning effects as alum 105). 

Artola A, Rigola M. 1992. Selection of optimum biological sludge for zinc removal from wastewater by a biosorption process. Biotechnol Lett 14(12) 1199-1204. 

Park D, Yun YS, Jo JH, Park JM (2006) Biosorption process for treatment of electroplating wastewater containing Cr(VI) laboratory-scale feasibility test. Ind Eng Chem Res 45 5059-5065. doi 10.1021/ ie060002d... 

G. Naja, C. Mustin, B. Volesky, and J. Berthelin. Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process. Chemosphere 62 163-170, 2006. 

The initial concentration of metal ion and bisorbent, pH and temperature are the operational conditions which influence the biosorption process. pH determines protonation or deprotonation of the functional groups in the biomass. It affects also the solution chemistry of metals and the competition of metal ions. For these reasons, pH has a strong effect on the biosorption process (Chojnacka, 2010). 

Cadmium and lead have been adsorbed onto a natural polysaccharide (sugar beet pulp) in a dynamic biosorption process coupled with tubular ceramic MF membrane (Reddad et al, 2003). A ceramic membrane (Zr02/Ti02) was used with a 0.14 or 1.4 mm cutoff and a total area of 94 cm. ... 

Since high levels of heavy metals can inhibit the growth of microorganisms when they are used as biosorbent materials, in some cases direct biological treatment is not usually feasible, and suitable pre-treatment is required. Ultrafiltration (UF) has been applied for the treatment of high metal-contaminated wastewater before of the biosorption process (Katsou et al, 2012 Malamis et al, 2010). UF membrane modules are able to retain suspended sohds (SS) and the majority of colloidal matter. Thus, metal forms attached to SS are effectivelyremovedbytheUF membranes. 

Tuzen, M., Sari, A., Mendil, D., Uluozlu, O.D., Soylak, M. Dogan, M. (2009) Characterization of biosorption process of As(lll) on green algae Ulothrix cylindricum. Journal of Hazardous Materials, 165,566-572. 

However, even though those models are used widely in the literature to predict metal-uptake capacity and differences in metal uptake between various species, they do not accurately represent the biosorption process. Both isotherms fail to take into account pH or the influence fi-om competing ions. Another significant flaw is the inability to extrapolate the data beyond the investigated set of parameters and any assumption or prediction will be instantly flawed. Furthermore, even though each system can describe quite truthfully each isotherm, they do not incorporate the effects of variability of external environmental factors. Thus they can be utilised in a controlled laboratory environment. However, it is when predicting a real scenario, these models are often found to be inadequate. ... 

The selector process is apphcable for readily degradable wastewaters it also requires upstream controls. In a selector, degradable organics are removed by the doc formers by biosorption and therefore are not available as a food source for the filaments. 

Biosorption. This process makes use of a phenomenon observed but ignored by many iavestigators. If activated sludge floe and raw sewage are mixed and aerated, there is first a significant reduction ia BOD of the efflueat. It is foUowed by a aotable BOD rise and then by a decrease. Originally,... 

Biosorption is a process that utilizes biological materials as adsorbents [Volesky, 1994], and this method has been studied by several researchers as an alternative technique to conventional methods for heavy metal removal from wastewater. 

Ahluwalia and Goyal94 have pointed out some disadvantages of biosorption such as the early saturation of biomass, which can be a problem since metal desorption is necessary prior to further use, irrespective of the metal value. Furthermore, the potential for biological process improvement is limited because cells are not performing an active metabolism. 

Biosorption is a rather complex process affected by several factors that include different binding mechanisms (Figure 10.4). Most of the functional groups responsible for metal binding are found in cell walls and include carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine, and imidazol moieties.4 90 The cell wall of plant biomass has proteins, lipids, carbohydrate polymers (cellulose, xylane, mannan, etc.), and inorganic ions of Ca(II), Mg(II), and so on. The carboxylic and phosphate groups in the cell wall are the main acidic functional groups that affect directly the adsorption capacity of the biomass.101... 

Spirodela intermedia, L. minor, and P. stratiotes were able to remove Pb(II), Cd(II), Ni(II), Cu(II), and Zn(II), although the two former ions were removed more efficiently. Data fitted the Langmuir model only for Ni and Cd, but the Freundlich isotherm for all metals tested. The adsorption capacity values (K ) showed that Pb was the metal more efficiently removed from water solution (166.49 and 447.95 mg/g for S. intermedia and L. minor, respectively). The adsorption process for the three species studied followed first-order kinetics. The mechanism involved in biosorption resulted in an ion-exchange process between monovalent metals as counterions present in the macrophytes biomass and heavy metal ions and protons taken up from water.112... 

Regarding submerged plants, sorption of Cu(II) by Myriophyllum spicatum L. (Eurasian water milfoil) has been shown to be fast and fits isotherm models such as Langmuir, Temkin, and Redlich-Peterson. The maximum sorption capacity (c/lll l j ) of copper onto M. spicatum L. was 10.80 mg/g, while the overall sorption process was best described by the pseudo-second-order equation.115 Likewise, Hydrilla verticillata has been described as an excellent biosorbent for Cd(II). In batch conditions, the qmsx calculated was 15.0 mg/g. Additionally, II. verticillata biomass was capable of decreasing Cd(II) concentration from 10 to a value below the detection limit of 0.02 mg/L in continuous flow studies (fixed-bed column). It was also found that the Zn ions affected Cd(II) biosorption.116... 

Quintelas, C., Sousa, E., Silva, F., Neto, S., and Tavares, T., Competitive biosorption of ortho-cresol, phenol, chlorophenol and chromium (VI) from aqueous solution by a bacterial film supported on granular activated carbon, Process Biochemistry, 4, 2087-2091, 2006. 

The sol-gel-entrapped microbial cells have shown excellent tolerance to different alcohols [99], The immobilized E. coli cells followed the Michaelis-Menten equation when quantified with the (3-glucosidase activity via the hydrolysis of 4-nitrophenyl-(3-D-galactopyranosdie [142], The sol-gel matrices doped with gelatin prevented the cell lysis, which usually occurs during the initial gelation process [143], Microorganisms are now widely used in the biosorption of different pollutants and toxicants. Bacillus sphaericus JG-A12 isolated from uranium mining water has been entrapped in aqueous silica nanosol for the accumulation of copper and uranium [144], Premkumar et al. [145] immobilized recombinant luminous bacteria into TEOS sol-gel to study the effect of sol-gel conditions on the cell response (luminescence). The entrapped and free cells showed almost the same intensity of luminescence (little lower), but the entrapped cells were more stable than the free cells (4 weeks at 4°C). This kind of stable cell could be employed in biosensors in the near future. 

As shown in Fig. 1 biosorption comprises a variety of processes including ion exchange, chelation, adsorption, and diffusion through cell walls and membranes all of which are dependent on the species used, the biomass origin and, and solution chemistry (Gavrilescu 2004). Biosorption is a fast and reversible process for removing toxic metal ions from solution. 

An electron microscopy study by Mullen et al. (1989) showed that Cd2+, Cu2+ and La3+ accumulated on the cell surface of Bacillus cereus, B. subtilis, E. coli and Pseudomonas aeruginosa as needle-like, crystalline precipitates, while Ag+ precipitated as discrete colloidal aggregates at the cell surface and occasionally in the cytoplasm. The needle-like and hexagonal precipitates were also found for the biosorption of Ni2+ on the cell surface of P. fluorescens 4F39 at pH 9 and it was suggested as a microprecipitation process that followed on ion exchange (Lopez et al. 2000). 

Srinath T, Verma T, Ramteke PW, Garg SK (2002) Chromium biosorption and bioaccumulation by chromate resistant bacteria. Chemosphere 48 427-435 Stephen JR, Macnaughton SJ (1999) Developments in terrestrial bacterial remediation of metals. Curr Opinion Biotechnol 10 230-233 Tabak HH, Lens P, van Hullebusch ED, Dejonghe W (2005) Developments in bioremediation of soils and sediments polluted with metals and radionuclides 1. Microbial processes and mechanisms affecting bioremediation of metal contamination and influencing metal toxicity and transport. Rev Environ Sci Bio/Technol. 4 115-156... 

Yilmaz El, Ensari NY (2005) Cadmium biosorption by Bacillus circulans strain EB1. World J Microbiol Biotechnol 21 777-779 Zouboulis AI, Loukidou MX, Matis KA (2004) Biosorption of toxic metals from aqueous solutions by bacteria strains isolated from metal-polluted soils. Process Biochem 39 909-916... 

The few reports on bioremediation of colored effluents by yeasts usually mention nonenzymatic processes as the major mechanism for azo dye decolorization [5-10]. In a first approximation based on the cellular viability status, these processes can be divided into two different types bioaccumulation and biosorption. Bioaccumulation usually refers to an active uptake mechanism carried out by living microorganisms (actively growing yeasts). The possibility of further dye biotransformation by redox reactions may also occur due to the involvement of... 

One of the first reports on yeast-mediated color removal by a putative process of biosorption of azo dyes by yeast (Rhodotorula sp.) biomass belongs to [31]. Yeast species such as Kluveromyces marxianus removed the diazo dye remazol black B [10], Candida catenulata and Candida kefyr removed more than 90% of amaranth by biosorption [6]. Biosorption uptake of the textile azo dyes remazol blue, reactive black, and reactive red by S. cerevisiae and C. tropicalis varied according to the selected dye, dye concentration, and exposure time [5, 7]. In a recent screening work carried out by [32], from the 44 yeast strains tested for their decolorization ability, 12 of them removed the dye Reactive Brilliant Red K-2BP by biosorption, among them the following were identified S. cerevisiae, Saccharomyces uvarum, Torulopsis Candida, and Saccharomycopsis lipolytica. 

Biosorption or bioaccumulation, the process of passive cations binding by dead or living biomass, represents a potentially consecutive way of removing toxic metals from industrial wastewaters. Biosorption could be employed most effectively in a concentration range below 100 mg L 1, where other techniques are inactive or too expensive. 

Pasyaka N (1997) State of LPO processes and AOS in children with severe form of acute pneumonia treated with Enterosgel. In Biosorption methods and preparations in prophylactic and therapeutic practice. First Conference, Kyiv (In Ukrainian), p 58... 

Francis (1990) has summarized the numerous possible microbially mediated reactions resulting in the mobilization or immobilization of metals and found that major interactions include oxidation-reduction processes, biosorption and immobilization by cell biomass and exudates, and mobilization by microbial metabolites. A profound issue in metal remediation is that through microbial action, metals can readily be re-mobilized, creating toxicity issues in sites where metals are not completely removed. 

Kumari, P., Sharma, P., Srivastava, S. and Srivastava, M.M. (2006) Biosorption studies on shelled Moringa oleifera Lamarck seed powder removal and recovery of arsenic from aqueous system. International Journal of Mineral Processing, 78(3), 131-39. 

Keywords Biosorption Activated sludge process Removal of heavy metals Sequential extraction of metals Metal uptake... 

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