Researchers at the Indian Institute of Technology (IIT) at Mandi have developed a fibrous membrane filter using a biopolymer-based material to remove heavy metals from water.
The research, which has been funded by the Ministry of Mines, has recently been published in the prestigious Elsevier journal, Polymer and the team plans to scale up the technology to industrial scales, to handle larger volumes of metal-contaminated water.
The paper has been co-authored by Sumit Sinha Ray, Assistant Professor at IIT Mandi's School of Engineering, and his research scholar Ashish Kakoria, along with Suman Sinha Ray, Adjunct Assistant Professor, the University of Illinois at Chicago.
"Acid mine drainage containing a large number of heavy metals is a menace. Heavy metals in water could lead to several neurological problems in human including Alzheimer's disease, Parkinson's disease, and multiple sclerosis, and it is important to develop filters to treat effluents that are released into water bodies to prevent pollution. Heavy metal pollution of water is a serious concern," Sumit Sinha Ray said.
"The problems of arsenic pollution in the Ganga basin are well known in India. The Indian National Science Academy reports that the major hazardous metals of concern for India in terms of their environmental load and health effects are lead, mercury, chromium, cadmium, copper, and aluminium, that are released into the water through anthropogenic activities such as mining, manufacturing, electroplating, electronics, and fertilizer production, among others," Ray added.
According to Ray, these membranes contain adsorbents materials that attract and hold the metals to the binding sites in question.
"In this work, we have provided a novel, industrially scalable method of production of adsorbents that can bind to heavy metals. One speciality of these adsorbents is that they contain a large amount of a biopolymer, Chitosan, derived from crab shells that are mixed with a well-known polymer, nylon. While normally the fibres used to make regular cartridge filter-assemblies are processed by a method called melt blowing, the team has used a process called 'solution blowing'," he said.
Solution blowing produces fibres that are nanometres in diameter a hundred thousand times thinner than a single human hair.
When the fibres get finer, their surface area increases tremendously, which results in better absorption of heavy metals.
"Apart from producing nanofibres, solution blowing processes can enable the blending of natural polymers like chitosan, lignin etc with synthetic polymers like Nylon, Poly(methyl methacrylate) etc. The replacement of synthetic polymers with natural polymers is a welcome move in this era of environmental consciousness," Ray said.
The IIT Mandi team claimed that using the solution blowing technique, they could replace 40 per cent of the nylon with chitosan, which means 40 per cent less fossil-fuel-derived polluting plastics.
"We have also observed that while normally adsorbent fibres bind to the target metal only at their surface, in their nanofibre membranes, the adsorption was seen to happen at the sub-surface scale as well, which translates to higher metal removal efficiency.
"The membranes could be reused at least eight times before there was a considerable reduction in the efficiency of metal adsorption. We tested with a prototype with four litres of heavy metal-laden water in the lab and have seen impressive results," he added.
