Biosorption biosorbents

Biosorbent Heavy metal Biosorption heat (kcal-mol" )... 

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... 

Biosorption strategies consist of a group of applications involving the detoxification of hazardous substances such as heavy metals instead of transferring them from one medium to another by means of biosorbents, which may be either microbes or plants. Biosorption options are generally characterized as being less disruptive and may henceforth be carried out on-site, thereby eliminating the need to transport the toxic materials to treatment sites.12 Biosorption is a very cost-effective method... 

A biosorption method for the separation of sulfur compounds from fossil fuels, by using a sulfur-biosorption agent and followed by the oxidation of the biosorbed complex. The oxidation is carried out in an aqueous phase containing an effective amount of oxygen and, optionally a biocatalyst, in which case an incubating stage is incorporated for the reaction to take place. 

Biomass derived from several industrial fermentations may provide an economical source of biosorptive materials. Many species have cell walls with high concentrations of chitin, a polymer of A-acetyl-glucosamine that is a very effective biosorbent. 

Biosorption promises to fulfill the requirements, which are competitive, effective, and economically viable. Efforts have been made to use different forms of inexpensive plant materials for the removal of toxic metals from the aqueous media. Some typical biosorbents explored so far in removing toxic metal ions from water bodies have been listed in Table 3.1. 

S-oxidizing bacteria), many are probably most appropriate for ex situ use in bioreactors, where the mobilized or immobilized metal can be separated from soil components (White et al., 1998). Living or dead fungal and bacterial biomass and metabolites have been used to remove metals, radionuclides, and metalloids from solution by biosorption or chelation (Macaskie, 1991 Gadd, 2001). The metalloregulatory protein MerR, which exhibits high affinity and selectivity toward mercury, was exploited for the construction of microbial biosorbents specific for mercury removal (Bae et ah, 2001, 2002, 2003). Whole-cell sorbents... 

Recently, new separation principles have been introduced and although these are very promising, they have not been extensively used for environmental analysis. Among them are FFF, pervaporation and biosorption. AU of them are easy to handle and not very expensive. In addition, FFF has very simple fundamental principles while pervaporation is very prone to automation and miniaturization. Biosorption is especially interesting for metal concentration because biosorbents can accumulate up to 25% of their dry weight in heavy metals. Some of the biosorbents are waste by-products of large scale industrial fermentations or certain abundant seaweeds. Analytes are easily released from the biosorbent and the biosorbent is regenerated for subsequent reuse. " ... 

Unfortunately, higher amoimts of some minerals in seaweed have been the result of pollution of the seawater or natural environment. Thus, many studies were conducted with respect to the contamination of seaweed by heavy metals. Because of their high sorption capacity, they were also probed for their utilization as biosorbents to remove heavy metals from the environment and to elucidate mechanisms of metal biosorption by seaweeds (Davis et al., 2003 Murphy et al., 2008 Suzuki et al., 2005). Further, these conclusions could be utilized for the understanding of the uptake mechanisms by seaweed. Finally, endogenous and exogenous factors have participated on the variability of seaweed mineral composition. 

Solution pH is an important parameter for the adsorption experiments. The effect of pH on adsorption was given in Figure 2. At lower pH, the amount of biosorption to Cu + is small. Biosorption to Cu + increases with the increase of pH from 2.5 to 4.5. The highest biosorption efficiency is observed in the pH range of 4.5-5.0. At low pH, the surface of biosorbent would... 

The kinetics of Cu + ion biosorption on aminated ephedra waste biosorbent were analyzed using pseudo-second order (Ho Mckay 1998) ... 

This preliminary study has shown that aminated ephedra waste biosorbent could be an interesting low-cost biosorbent for copper removal from aqueous solutions. The optimum absorption conditions of aminated ephedra waste pH is 4.7 contact time is 3 h Pseudo-second-order model is more applicable for the adsorption process. The biosorption of Cu + on aminated ephedra waste biosorbent obeys the Langmuir isotherm. According to the Langmuir equation, the maximum adsorption capacities of modified adsorbent for Cu + are 93.11 mg/g. The results obtained with aminated ephedra waste may be tested using metal-industry wastewater containing Cu +, since ephedra waste is an inexpensive source and therefore may have the advantage of economic viability. 

In the experiments carried out by Buasri et al. on the removal of and Zn ions from aqueous solution onto modified cellulose and corn cob, respectively, with phosphoric acid, the influence of the different initial biomass concentration was studied. The number of sites available for biosorption depends upon the amount of the biosorbent. In all cases it was observed that an increase of the biosorbent concentration lead to an increase in the metal ion uptake. They concluded that the optimum S L ratio was 3 g/100 mL. Beyond this dosage there is a rise in the biomass surface area and in the number of potential binding sites. In the same studies the influence of the temperature on the adsorption process was evaluated. An increase of temperature leads to activation of the metal ions and their binding by the adsorbent coordinating site is enhanced, so the metal uptake is favored. In these studies the maximum adsorption capacities for Zn and Cu onto the modified cellulose and corn cob, respectively, with phosphoric acid, was obtained at 70 °C when 1 g of biomass was used for an initial concentration of 500 ppm of metal ions. ... 

The term biosorption is given to adsorption processes, which use biomaterials as adsorbents (or biosorbents). Chitosan is a biopolymer and has an extremely high affinity for many classes of dyes, including disperse, direct, reactive, acid, vat, sulfur, and naphthol dyes (Figure 39.3). The rate of diffusion of dyes in chitosan is similar to that in cellulose. Only for basic dyes has chitosan a low affinity. 

The relationship between metal ionic characteristics and the maximum biosorption capacity was estabUshed using QSAR models based on the classification of metal ions (soft, hard, and borderhne ions). Ten kinds of metal were selected and the waste biomass of Saccharomyces cerevisiae obtained from a local brewery was used as biosorbent. Eighteen parameters of physiochemical characteristics of metal ions were selected and correlated with Ths suggestion was made that classification of metal ions could improve the QSAR models and different characteristics were significant in correlating with ax, such as polarizing power Z /r or the first hydrolysis constant logRo or ionization potential IP. 

Biosorption is an efficient and economical method that can be used for the removal of heavy metals from wastewaters. The majority of recent biosorption smdies were conducted with low-cost agricultural waste such as sunflower stalks [14,15], orange peel [16], coconut cash [17,18], ohve stone [19, 20], steel-making slag [21], tree fern [22], olive tree pruning [23], rice husk [24], peanut hull pellets [25], and grape stalk [26,27], and all of them have been identified as potential biosorbents for heavy metal removal. 

Farooq U, Khan MA, Atharc M, Kozinski J A. Effect of modification of environmentally friendly biosorbent wheat (Triticum aestivum) on the biosorptive removal of cadmium(II) ions from aqueous solution. Chem Eng J 2011 171 400-410. 

In the second hybrid system, the membrane is the first step and the membrane permeate is fed to the biosorption step for post-treating with the biosorbent material. Also, the membrane is used to separate suspended particles which cause reduction of biosorbent materials efficiency. Figure 7.4 presents these categories. 

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. 

In this section, a summary of recent information concerning bioadsorption of arsenic (As), uranium (U) and fluoride (F ) has been provided. The reader is strongly encouraged to refer to the original research papers for information on experimental conditions. A summary of biosorption capacity of various biosorbents for removal of F, As and U has been presented in Table 7.2. 

Table 7.2. Biosorption capacity for the removal of fluoride, arsenic and uranium by various biosorbents. ...

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