Hexavalent Chromium (VI)

Hexavalent chromium (Cr (VI)) is widely used in various process industries such as leather tanning, pigments and paints, mining, textile dyeing, electroplating, pulp and paper, aluminum conversion coating operations etc. It is a toxic heavy metal often existing in the industrial waste stream. Cr (VI) is known to be a strong oxidant and an acute carcinogen [1]. Therefore the removal of Cr (VI) from waste streams is essential to protect environmental health. The permissible level of Cr (VI) for discharge into surface water is 0.1 mg/L and portable water is 0.05 mg/L [2,3]. The Ministry of Environment and Forest (MOEF);Government of India has set Minimal National Standard (MINAS) of 0.1 mg/L for safe discharge of chromium containing effluent to

The conventional techniques for removing heavy metals from industrial wastewaters are precipitation [5], adsorption [6], reduction [7], membrane process [8], ion exchange [9] and solvent extraction [10]. In addition, these conventional treatment processes are limited due to technological or economic constraints. However, biosorption represent attractive and cost effective alternative for decontamination of ionic pollutants such as heavy metal ions. Bacteria, fungi, algae and agricultural waste are considered as the class of biosorbent [11]. Several recent publications were utilized for various inexpensive and locally abundantly available biosorbents like barley straw [12], peanut hulls [13], neem bark [14], waste tea leaves [15],sago waste[16],hazel nut shell [17],cocoa shells [18], tea waste [19], palm kernel fibre [20] and orange peels [21]. Among these biosorbent, seaweeds are inexpensive and abundantly available. It is based on the submissive withholding of metal ions by functional groups and active sites present in the biomass [22-24]. It has numerous discrete advantages over other conventional techniques such as low-cost, eco-friendly, high efficiency, without additional nutrient supply, regeneration of biosorbent and feasibility of metal extraction etc.,

The collected alga was washed with deionized (DI) water several times to remove impurities. The washing process continued until the pH of wash solution was equal to DI water. The washed algae were then wholly dried in sunlight for ten days. Dried weight of algae was incurred after drying it at 105°C for 24 hours. Dry algae were then sliced in to small pieces and were pulverized using domestic mixer. In this study the dry powder biomass in the range of 0.176mm to 1.503mm particle size were utilized for sorption experiments without any chemical