G K Suraishkumar

In this study, biosorption of Cu(II) was investigated in a column of pretreated Aspergillus niger biomass. The breakthrough was measured as a function of influent flow rate and bed height for a feed solution at 10 mg/l metal ion concentration. Biosorption was evaluated in terms of the equilibrium capacity of the column and the amount of metal loading on the A. niger surface. It has been observed that pretreatment of the biomass enhanced the activity of the surface reactive groups and hence the uptake. The breakthrough data obtained was described by bed depth service time (BDST) and Thomas models. The amount of copper adsorbed per gram of pretreated A. niger was 13.4 ± 0.60 mg/g. The sorbed copper was eluted from the column using 0.1N HCl in five consecutive sorption-desorption cycles. For the same initial metal ion concentration, a packed column reactor shows more uptake of Cu(II) in comparison to a batch reactor. © 2008 Elsevier B.V. All rights reserved.

Sustainable development requires wastewater management. Heavy metals such as copper, cadmium, lead and zinc are the critical metals in wastewater. The treatment of wastewater is vital functions in any society; hence securing them for current and future generations is an important part of sustainable development. The main objective of this work is to increase water use efficiency and recycling water which is an integrated approach to sustainable development. In this present work, copper biosorption by formalin washed Aspergillus niger was characterized. The nature and binding mechanism of chemical groups in the formalin washed biomass responsible for copper biosorption was investigated as a function of pH and metal concentration, combined with Scanning Electron Micrograph (SEM), Image Analysis System (IAS), a nitrogen adsorption-desorption technique and Fourier transform infrared spectroscopy (FTIR). The retention capacity of the biomass was determined at pH 6.0 to be equal to 23.62 mg of copper/g of biomass. The Langmuir and Freundlich isotherm equations were then used to describe the behavior of the system. Based on the experimental data and surface analysis an efficient method was established for copper removal from wastewater so that it can be reused for domestic cleaning and industrial reuse.

Treatment of microbial cultures with chemical agents such as hydrogen peroxide (H2O2) and hypochlorous acid (HOCl) induces production of reactive oxygen species (ROS) in culture. These ROS inducing (treatment) agents increased the growth rate as well as the maximum specific levels of extracellular enzymes such as α-amylase and protease in Bacillus subtilis cultures. Treatment with hypochlorous acid increased maximum specific α-amylase level by 2.2-fold and maximum specific protease level by 2.6-fold, respectively. Similarly, treatment with H2O2 increased specific α-amylase and specific protease level by 1.5- and 1.9-fold, respectively. Increases in specific enzyme levels were correlated with levels of specific intracellular ROS in cultures. The mechanism of increase in enzyme productivity under induced oxidative stress was also traced at the genetic level through analysis of available microarray data. The microarray data showed an induced level of signal peptidase gene (sipT), which is the most important secretory apparatus component, and suggested that increased efficiency of secretory apparatus as a result of treatments with ROS inducing agents also leads to increased productivity of α-amylase. © 2004 Elsevier Ltd. All rights reserved.

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. © 2006 Elsevier Ltd. All rights reserved.