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Project title

The development of a bioremediation product: A study of factors affecting biosorption of chromium by a variety of seaweed species.

Primary Funding Agency

Environmental Protection Agency

Co-Funding Organisation(s)

n/a

Lead Organisation

Waterford Institute of Technology (WIT)

Lead Applicant

Peter McLoughlin

Project Abstract

Heavy metal pollution is a worldwide environmental problem. The presence of heavy metals in the environment is of major concern due to their toxicity and threat to plant and animal life. Effluents from various industrial processes represent one of the most important sources of heavy metal pollution. Chromium is commonly used in industrial application such as in tanning processes electroplating pigmentation catalyst for corrosion inhibitors and wood preservatives [1]. While hexavalent (HCrO-4 and Cr2O72-) and trivalent (Cr3+ and CrOH2+) species of chromium are prevalent in industrial waste solutions the hexavalent form has been considered more hazardous to public health due to its mutagenic and carcinogenic properties [2]. Both the World Health Organisation and the US EPA has set the maximum contaminate level for Cr(VI) in domestic water supplies at 0.05 mg L-1 [3]. Over the past two decades much attention has been focussed on identifying materials that are capable of effectively removing heavy metals from aqueous environments. One such group of materials are known as biosorbents and the passive binding of metals by living or dead biomass is commonly referred to as biosorption [4]. Biosorption exploits the ability of microbial or plant biomass to sequester heavy metal ions from aqueous solution [5]. Various biomaterials have been examined for their biosorptive properties and different biomass types have shown different levels of metal uptake [6]. Among the biomaterials studied seaweeds were found to be extremely efficient biosorbents with the ability to bind a variety of metals [7]. In particular the potential of nonviable seaweeds in the recovery of heavy metal ions from aqueous effluents has been studied [89]. Seaweeds possess a high metal binding capacity [610] where the cell wall plays an important role in metal binding [1112]. This is due to the presence of various functional groups such as carboxyl sulphate and hydroxyl groups which can act as binding sites for metals. The main mechanisms for this include ionic interactions and complex formation between metal cations and ligands contained within the structure of the biomaterials [8].Biosorption may be based on one or more of the following mechanisms: ion-exchange physical adsorption complexation and precipitation. These mechanisms may differ quantitatively and qualitatively according to the type of biomass its origin and the processing to which it has been subjected. In many biosorption processes more than one of these mechanisms takes place simultaneously and it is difficult to distinguish between the single steps [13]. Although the metal binding properties of seaweeds have been widely studied the mechanisms responsible are still relatively poorly understood. Many of the studies to date on metal biosorption by seaweeds have been focussed exclusively on brown seaweeds such as Sargassum sp.[14-20] and Ecklonia sp. [21-24] with red and green seaweeds studied to a lesser degree. Lee et al. [25] investigated the uptake capacities of 48 red green and brown seaweeds for hexavalent chromium while Hashim et al. [26] studied the biosorption of cadmium by seven species of brown red and green seaweeds.Surface biosorption is the first line of defence seaweed possess in response to heavy metal ion pollution. They also possess cellular proteins which bind the metals and store them in compartments within the cell or exclude them to the surrounding environment. The metal binding proteins are believed to be algal metallothioneins (phytochelatins) [2728]. Metallothioneins are low molecular weight cysteine rich polypeptides that complex i'softi metal ions in thiol clusters. There are three classes of metalothionenins however eukaryotic algae only posses class III metalothioneins also referred to as phytochelatins. The function of these proteins is to chelate toxic trace metals thereby reducing the concentration of cytotoxic free metal ions. These proteins are also believed to be involved in zinc and copper homeostasis. These proteins are not primary gene products however the gene encoding the enzyme phytochelatin synthase which synthesises phytochelatins in vivo is an inducible gene. Therefore seaweed contains very low cellular phytochelatins which is augmented rapidly during heavy metal pollution [29-31].It is the aim of this study to investigate the biosorptive properties of three different seaweed species and to investigate the parameters which could enhance chromium biosorption with the future development of an inexpensive natural biomass with the capability of detoxifying chromium contaminated aqueous solutions.

Grant Approved

�40,000.00

Research Hub

Natural Environment

Research Theme

Protecting our Water Resources

Start Date

09/10/2006

Initial Projected Completion Date

08/10/2008