Employing waste to manage waste: Utilizing waste biomaterials for the elimination of hazardous contaminant [Cr(VI)] from aqueous matrices.

Pollution caused due to discharge of toxic and hazardous chemical contaminants from industrial processes is an issue of major environmental concern. Hexavalent chromium [Cr(VI)] is one such known toxic heavy metal contaminant emanated largely from various industrial processes. Since physical-chemical treatment techniques are beset with several problems, there is an increased attention on the use of waste biomaterials/biomass as sorbents for the elimination of heavy metals from aqueous matrices. The main purpose of this study was to evaluate the effectiveness of some low-cost waste biomaterials such as fruit wastes, agricultural and industrial waste/byproducts, waste parts of photosynthetic plants, aquatic plants and fungal biomass collected from different sources for the biosorption of Cr(VI) from aqueous matrices. Amid the tested biomaterials, wood apple shell (WAS) biomass (Limonia acidissima) was found to be highly efficient biosorbent for Cr(VI) sorption. In majority of biomass, it was observed that biosorption of Cr(VI) took place at acidic pH with optimum pH ranging from 2.0 to 5.0. Loading capacity of WAS biomass (29.37 mg/g) was higher than that of conventional adsorbent activated charcoal (26.56 mg/g), which was used as control. Cr(VI) treated biomass (WAS) was characterized using instrumental techniques such as Scanned Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) confirmed the adsorption of Cr(VI). Boehm titration and FTIR studies were conducted to ascertain the presence of functional groups responsible for Cr(VI) sorption by WAS biomass. The WAS biomass removed Cr(VI) from industrial wastewater with an efficiency of >99.9% thus complying with the statutory limits. Considering the economical aspect, the selected biomass can be viewed as a potential candidate for the elimination of toxic contaminant from wastewater.

Biomanagement of hexavalent chromium: Current trends and promising perspectives.

Chromium (Cr) is most widely used heavy metal with vast applications in industrial sectors such as metallurgy, automobile, leather, electroplating, etc. Subsequently, these industries discharge large volumes of toxic Cr containing industrial wastewaters without proper treatment/management into the environment, causing severe damage to human health and ecology. This review gives some novel insights on the existing, successful and promising bio-based approaches for Cr remediation. In lieu of the multiple limitations of the physical and chemical methods for remediation, various biological means have been deciphered, wherein dead and live biomass have shown immense capabilities of removing/reducing and/or remediating Cr from polluted environmental niches. Adsorption of Cr by various agro-based waste and reduction/precipitation by different microbial groups have shown promising results in chromium removal/recovery. Various microbial based agents and aquatic plants like duckweeds are emerging as efficient adsorbents of metals and their role in chromium bioremediation is an effective green technology that needs to be harnessed effectively. The role of iron and sulphur reducing bacteria have shown potential for enhanced Cr remediation. Biosurfactants have revealed immense scope as enhancers of microbial metal bioremediation and have been reported to have potential for use in chromium recovery as well. The authors also explore the combined use of biochar and biosurfactants as a potential strategy for chromium bioremediation for the development of technology worth adopting. Cr is non-renewable and finite resource, therefore its safe removal/recovery from wastes is of major significance for achieving social, economic and environmental sustainability.