Elsevier

Bioresource Technology

Volume 98, Issue 9, July 2007, Pages 1781-1787
Bioresource Technology

Kinetic modeling for the biosorption of copper by pretreated Aspergillus niger biomass

https://doi.org/10.1016/j.biortech.2006.06.025Get rights and content

Abstract

In this present work, a kinetic model for biosorption of copper was developed considering the possibility of different forms of functional groups being present on the surface of the biomass prepared from Aspergillus niger. Results showed that metal uptake by A. niger was a mass transfer driven process, requiring only 30 min to achieve 70% adsorption efficiency. Copper sorption by A. niger was influenced by the biomass dose, initial metal ion concentration, and pH of the solution. The Langmuir and Freundlich adsorption isotherms were used to describe the behavior of the system at different pH. The retention capacity of the biomass was determined at pH 6.0 to be equal to 23.62 mg/g of biomass. The pretreatment with formalin improved the uptake of metal ion.

Introduction

Environmental contamination is a major problem being faced by the society today. Heavy metal removal from wastewater is important for the protection of the environment and human health. One of the more important toxic metals, copper, finds its way to the water stream from industries like electroplating, mining, electrical and electronics, iron and steel production, the non-ferrous metal industry, the printing and photographic industries and metalworking and finishing processes (Brauckmann, 1990). The effects of acute copper poisoning in humans and plants are very serious, in particular possible liver damage with prolonged exposure. Strict environmental regulations have enhanced the demand for new technologies for metal removal from wastewater to attain toxicity driven limits.

Previous studies have reported the use of biosorption methods for removal and recovery of heavy metals from contaminated industrial effluents. Biosorption has been investigated in recent years with a focus on different biomasses (Brierley, 1990). It has been reported that bacteria, fungi, yeast and algae can remove heavy metals in reasonably good amounts from aqueous solutions (Gadd, 1988). The biomass can be cheaply and easily procured as a byproduct from the established industrial fermentation processes, for the biosorption of heavy metals (Muraleedharan et al., 1991) that can also result in value addition for the waste biomass along with a reduction in biomass disposal costs.

Many reports exist on work to identify suitable and relatively cheap biosorbents, which are capable of removing copper ions (Schiewer and Wong, 1999, Esposito et al., 2001). Biosorption by Aspergillus niger has been identified for its potential to remove metals (Mukhopadhyay et al., 2006a, Mukhopadhyay et al., 2006b) due to its availability from various industrial fermentation processes. Kapoor and Viraraghavan, 1997, Kapoor and Viraraghavan, 1998, Kapoor et al., 1999 performed experiments with raw and pretreated A. niger to determine the effectiveness of the biomass for removal of lead, cadmium, copper and nickel. They showed that the various functional groups in the cell wall of A. niger are responsible for biosorption. In addition they showed that pretreatment increases adsorption capacity of the biomass for all metals but the magnitude of increment depends on the type and method of pretreatment.

There is no information in the literature on any mechanistic study of adsorption capacity as a function of the surface groups on biomass. These surface groups, which are responsible for biosorption of copper, are strongly affected by the pH of the solution. It is expected that different functional groups are active at different solution pH. The main objective of this study was to propose a kinetic model for the biosorption of copper by pretreated A. niger to support the experimental data at different operating conditions such as initial biomass concentration, initial metal ion concentration of the metal and pH of the solution.

Section snippets

Growth of culture

The fungus A. niger strain NCIM 618 (ATCC 10594), was obtained from NCIM, Pune, India. It was propagated on potato dextrose agar (PDA) 39 g/l and yeast extract 0.1 g/l for 5–7 days at 33 ± 2 °C. Fungal biomass was cultivated in liquid medium containing (g/l): dextrose, 30; peptone 10; (NH4)2HPO4, 0.4; KH2PO4, 0.2; MgSO4, 7H2O, 0.2. All reagents were from Himedia, or Merck (Mumbai, India). The pH of the growth medium was adjusted to 5.8–6.0 by the addition of 0.1 N HCl prior to autoclaving. After

Kinetic modeling

The biomass structure is complex in nature. From a biosorption perspective it may be assumed to contain combination of different active functional groups as determined by FTIR measurements (Mukhopadhyay et al., 2006a, Mukhopadhyay et al., 2006b). These groups are involved in the reaction and responsible for the biosorption capacity. At different pH different groups are dominating and participating in the complexation process. pH dependence of surface reactive groups is presented in Eq. (1).H2RG+

Results and discussion

Table 1 shows the biosorption characteristics of different biomasses for Cu(II) removal. Pretreatment of the biomass was performed following the work of (Kapoor and Viraraghavan, 1997, Kapoor and Viraraghavan, 1998, Kapoor et al., 1999). Formalin pretreatment significantly improved the surface active site that actually participates in Cu(II) sorption. Mukhopadhyay et al., 2006a, Mukhopadhyay et al., 2006b used infrared spectroscopy (IR) to characterize the raw biomass and reported the presence

Conclusions

The results obtained in this study on kinetic data could be useful for the design of a wastewater plant. A comparative data of adsorptive capacity indicated that the prepared biomass surface had more affinity for Cu(II).

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