Title : Sustainable composite coagulants for the removal of emerging pollutants from the aqueous systems
The conventional water treatment methods are not suitable for removing hazardous pollutants from the aqueous systems. These methods are mainly removing the suspended matters present in water. But, due to natural and anthropogenic activities, water is contaminated with heavy metals, fluorides, arsenic, pesticides etc. These materials are in dissolved form and the present system of water purification cannot remove these pollutants within specified limit. Some of these materials are carcinogenic, teratogenic, mutagenic and endocrine destructive chemicals. So, a water treatment technique which can remove both the suspended and dissolved matters that are hazardous to health is novel. Heavy metal pollution in aqueous systems is a major problem faced in the water treatment field. Major heavy metal pollutants are cadmium, chromium, lead etc. Due to their hazardous effects to living beings, great attention is needed for the removal of such emerging contaminants from aqueous systems. Presently in developing countries, coagulation with synthetic coagulants such as alum is used for water treatment which produces aluminium as secondary pollutant. Excess limits of aluminium causes Alzhimer’s disease and it is neuro toxic. Nowadays, great attention is taken for producing natural green materials for removing hazardous contaminants from both water and waste water. They are non-toxic and do not produce secondary pollution and removes both suspended and dissolved matters simultaneously. Aqueous systems contain many pollutants which change from time to time. So, a single coagulant cannot remove all the pollutants at a time. Complex structural and functional properties are obtained by preparing composite coagulants. Natural polymers as coagulant and clay as adsorbent are used for preparing novel composite coagulants. Solution processing method is most suitable for preparing clay polymer nanocomposites because, many natural polymers are water soluble in nature and clay layers are separated by water molecules and make intercalated or exfoliated layered-silicate polymer composites. In this study, clay-polymer nanocomposites were prepared by using biopolymers of Moringa oleifera seed and gum with bentonite clay for removing emerging heavy metal pollutants such as cadmium, chromium and lead. The surface morphology and surface functionality of the adsorbents were studied using Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The functional and structural characteristics of newly synthesized clay-polymer composites were determined by Fourier Transform Infrared Spectrometer (FTIR) and Powder X-ray Diffraction (P-XRD) techniques. Method used in this study for removing heavy metal ions present in aqueous systems is coagulo-adsorption and double filtration using clay-polymer composite. The results show that clay-polymer composites remove the heavy metals concentration below the standard limits of drinking water as per standards. FTIR analysis of composite coagulants before and after metal adsorption revealed the presence of various functional groups which participate in the adsorption of heavy metal ions. Also, the SEM and TEM images of the adsorbent before and after heavy metals reveal that clay-polymer composite have high possibility to be used as effective and economical adsorbent for heavy metal removal for water supply schemes.
Audience take away:
- Though lot of work has been done on the use of clay and organic polymers, approach of developing a clay-polymer nanocomposite as new green composite coagulo-adsorbent for water treatment seems to be original and novel.
- Using standard procedures preparation of bentonite clay and the Moringa oleifera seed and gum polymers has been carried out and the clay-polymer composites have been prepared. Green composites obtained have been analyzed before and after coagulation/adsorption of various heavy metals using sophisticated instrumentation and techniques likes FTIR, SEM, TEM, XRD etc. to determine the efficiency and mechanism of heavy metal removal by the composites. Though information on the instrumentation, their working and application have been given more details on the sample preparation and handling, instrumental procedure and the parameter used may give more insight to the researchers working on the similar aspects.
- Important part of the study is experiments carried out using jar/bucket and double filtration studies to demonstrate the efficacy for heavy metal removal by coagulo-adsorption processes. The result and data obtained have shown successful development of the green organobentonite composites. The results are also promising for the removal of heavy metals like cadmium, chromium and lead. It also proposes and recommend a model river/pond water treatment plant for the polluted waters leading to supply of potable water.