**Removal of Hexavalent Chromium from Solutions and Contaminated Sites by Different Natural Biomasses**

Ismael Acosta-Rodríguez, Juan F. Cárdenas-González, María de Guadalupe Moctezuma-Zárate and Víctor M. Martínez-Juárez

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/56152

**1. Introduction**

[67] Shen H, Wang Y T. Modeling hexavalent chromium reduction in Escherichia coli

[68] Mtimunye PJ. Steady-state model for hexavalent chromium reduction in simulated biological reactive barrier: microcosm analysis. Master's Thesis. University of Preto‐ ria, Pretoria, South Africa; 2011. http://upetd.up.ac.za/thesis/available/

ATCC 33456. Biotechnology and Bioengineering 1994; 43(4) 293-300.

etd-09222011-104550/ (accessed on 30/10/2012).

206 Applied Bioremediation - Active and Passive Approaches

Chromium (Cr) toxicity is one of the major causes of environmental pollution emanating from tannery effluents. This metal is used in the tanning of hides and leather, the manufacture of stainless steel, electroplating, textile dyeing and as a biocide in the cooling waters of nuclear power plants. Consequently, these industries discharged chromium (VI) bearing effluents which are of significant environmental concerns [1]. Cr exists in nine valence states ranging from -2 to +6. From these, only the hexavalent [Cr (VI)] and trivalent chromium [Cr (III)] have primary environmental significance since they are the most stable oxidized forms in the environment.

Both are found in various bodies of water and wastewaters [2]. Cr (VI) typically exists in one of these two forms: chromate (CrO4 -2) or dichromate (Cr2O7 -2), depending on the pH of the solution [2].These two divalent oxyanions are very water soluble and poorly adsorbed by soil and organic matter, making them mobile in groundwater. Both chromate anions represent acute and chronic risks to animals and human health, since they are extremely toxic, mutagenic, carcinogenic and teratogenic [3]. In contrast to Cr (VI) forms, the Cr (III) species are predom‐ inantly hydroxides, oxides and sulphates, less water soluble, less mobile, 100 times less toxic [4] and 1,000 times less mutagenic [5]. The principal techniques for recovering or removing Cr (VI), from wastewater are: chemical reduction and precipitation, adsorption on activated carbon, ion exchange and reverse osmosis [6]. However, these methods have certain draw‐ backs, namely high cost, low efficiency, generation of toxic sludge or other wastes that require

© 2013 Acosta-Rodríguez et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. disposal and imply operational complexity [7]. In this context, considerable attention has been focused in recent years upon the field of biosorption for the removal of heavy metal ions from aqueous effluents [8].

temperature on Cr (VI) sorption by natural biomass, was determined at pH values of 1, 2, 3, and 4, 28°C, 40°C, and 50°C, respectively. The effect of different doses of biomass ranging from 1 to 5 g/L, with 100 mg/L of Cr (VI) concentrations was determined. The values shown in the

Removal of Hexavalent Chromium from Solutions and Contaminated Sites by Different Natural Biomasses

Four 250 mL Erlenmeyer glass flasks, with 5 g of shell biomass, were added with 20 g of contaminated earth and water with 297 mg Cr (VI)/g earth or 373 mg Cr(VI)/L water, of tannery (Celaya, Guanajuato, México), and the volume was complete to 100 mL with trideionized water. The mixture was shaken in a rotary shaker at 120 rpm followed by filtration using Whatman filter paper No. 1. The filtrate containing the residual concentration of Cr (VI) was

Hexavalent and trivalent chromium were quantified by a spectrophotometric method employing diphenylcarbazide and chromazurol S, respectively [19, 20], and total Chromium

Figure 1 shows the effect of the incubation time and pH on Cr (VI) removal by *L. chinensis* Sonn shell. The optimum time and pH for Cr (VI) removal are 10 min and pH 1.0, at constant values of biosorbent dosage (1 g/100 mL), initial metal concentration (100 mg /L) and temperature (28°C). The literature [11], report an optimum time of 60 min., for the removal of lead by orange waste, 30 min and 60 for the removal of Cr (VI) by the tamarind peel and eucalyptus bark [12, 16]. Changes in the permeability of unknown origin, could partly explain the differences found in the incubation time, providing greater or lesser exposure of the functional groups of the cell wall of biomass analyzed. Adsorption efficiency of Cr (VI) was observed maximum at pH 1.0

which were expected to interact more strongly with the ligands positively charges [21]. These results are like for tamarind peel [10], but the most of authors report an optimum pH of 2.0 like tamarind seeds [10], eucalyptus bark [16], bagasse and sugarcane pulp, coconut fibers and wool, [22], for the tamarind fruit shell treated with oxalic acid [23], at pH of 2.0 and 5.0 for the

Temperature is found to be a critical parameter in the bioadsorption of Cr (VI) by *L. chinensis* Sonn shell (Figure 2). The highest removal was observed at 40 and 50°C. At this point the total removal of the metal is carried out. The results are coincident for tamarind seeds with 95% of

2- and Cr2O7

2-) of Cr ions in solution

http://dx.doi.org/10.5772/56152

209

results section are the mean from three experiments carried out by triplicate.

**2.4. Bioremediation assay**

determined with 1, 5 diphenylcarbazide [19].

**3. Results and discussion**

**3.1. Effect of incubation time and pH**

**2.5. Determination of hexavalent, trivalent and total Cr:**

by Electrothermal Atomic Absorption Spectroscopy [19].

with Litchi shell. This was due to the dominant species (CrO4

**3.2. Effect of temperature on Cr (VI) removal by** *L. chinensis* **Sonn shell**

mandarin bagasse [24] and almond green hull [25].

The process of heavy metal removal by biological materials is known as biosorption. Biomass viability does not affect the metal uptake. Therefore any active metabolic uptake process is cur‐ rently considered to be a negligible part of biosorption. Various biosorbents have been tried, which include seaweeds, molds, yeast, bacteria, crab shells, agricultural products such modi‐ fied corn stalks, [9], hazelnut shell [10], orange waste [11] and tamarind peel [12]. It has also been reported that some of these biomass can reduce chromium (VI) to chromium (III), like *Litchii cinensis* Sonn peel [13], tea fungal biomass [14], Mesquite [15], Eucalyptus bark [16], red rose's waste biomass [17] and Yohimbe bark [18]. The present study is undertaken with follow‐ ing objective: Investigate the use of different natural biomasses for the biosorption and reduc‐ tion of Chromium (VI) in aqueous solution, and their elimination from contaminated sites.
