Removal of heavy metal ions from wastewaters: A review

Slow-pyrolysis of biomass for the production of biochar, a stable carbon-rich solid by-product, has gained considerable interest due to its proven role and application in the multidisciplinary areas of science and engineering. An alternative to slow-pyrolysis is a relatively new process called hydrothermal carbonization (HTC) of biomass, where the biomass is treated with hot compressed water instead of drying, has shown promising results. The HTC process offers several advantages over conventional dry-thermal pre-treatments like slow-pyrolysis in terms of improvements in the process performances and economic efficiency, especially its ability to process wet feedstock without pre-drying requirement. Char produced from both the processes exhibits significantly different physiochemical properties that affect their potential applications, which includes but is not limited to carbon sequestration, soil amelioration, bioenergy production, and wastewater pollution remediation. This paper provides an updated review on the fundamentals and reaction mechanisms of the slow-pyrolysis and HTC processes, identifies research gaps, and summarizes the physicochemical characteristics of chars for different applications in the industry. The literature reviewed in this study suggests that hydrochar (HTC char) is a valuable resource and is superior to biochar in certain ways. For example, it contains a reduced alkali and alkaline earth and heavy metal content, and an increased higher heating value compared to the biochar produced at the same operating process temperature. However, its effective utilization would require further experimental research and investigations in terms of feeding of biomass against pressure; effects and relationships among feedstocks compositions, hydrochar characteristics and process conditions; advancement in the production technique(s) for improvement in the physicochemical behavior of hydrochar; and development of a diverse range of processing options to produce hydrochar with characteristics required for various industry applications.

A comparative review of biochar and hydrochar in terms of production, physico-chemical properties and applications

Adsorption of heavy metals on conventional and nanostructured materials for wastewater treatment purposes: A review

The controversy related to the environment pollution is increasing in human life and in the eco-system. Especially, the water pollution is growing rapidly due to the wastewater discharge from the industries. The only way to find the new water resource is the reuse of treated wastewater. Several remediation technologies are available which provides a convenience to reuse the reclaimed wastewater. Heavy metals like Zn, Cu, Pb, Ni, Cd, Hg, etc. contributes various environmental problems based on their toxicity. These toxic metals are exposed to human and environment, the accumulation of ions takes place which causes serious health and environmental hazards. Hence, it is a major concern in the environment. Due to this concern, the significance of developing technology for removing heavy metals has been increased. This paper contributes the outline of new literature with two objectives. First, it provides the sketch about treatment technologies followed by their heavy metal capture capacity from industrial effluent. The treatment performance, their remediation capacity and probable environmental and health impacts were deliberated in this review article. Conclusively, this review paper furnishes the information about the important methods incorporated in lab scale studies which are required to identify the feasible and convenient wastewater treatment. Moreover, attempts have been made to confer the emphasis on sequestration of heavy metals from industrial effluent and establish the scientific background for reducing the discharge of heavy metals into the environment.

Efficient techniques for the removal of toxic heavy metals from aquatic environment: A review

Water pollution is a global problem threatening the entire biosphere and affecting the life of many millions of people around the world. Not only is water pollution one of the foremost global risk factors for illness, diseases and death, but it also contributes to the continuous reduction of the available drinkable water worldwide. Delivering valuable solutions, which are easy to implement and affordable, often remains a challenge. Here we review the current state-of-the-art of available technologies for water purification and discuss their field of application for heavy metal ion removal, as heavy metal ions are the most harmful and widespread contaminants. We consider each technology in the context of sustainability, a largely neglected key factor, which may actually play a pivotal role in the implementation of each technology in real applications, and we introduce a compact index, the Ranking Efficiency Product (REP), to evaluate the efficiency and ease of implementation of the various technologies in this broader perspective. Emerging technologies, for which a detailed quantitative analysis and assessment is not yet possible according to this methodology, either due to scarcity or inhomogeneity of data, are discussed in the final part of the manuscript.

Sustainable technologies for water purification from heavy metals: review and analysis

Removal of heavy metal from industrial wastewater using modified activated coconut shell carbon

Coagulation/flocculation process and sludge conditioning in beverage industrial wastewater treatment.

Coagulation/flocculation process in the treatment of abattoir wastewater

Performance optimization of coagulant/flocculant in the treatment of wastewater from a beverage industry

Attempts were made to compare the adsorption efficiency of coconut shell-based granular activated carbon with the adsorption efficiency of commercial carbon, Calgon carbon F-300, with respect to adsorption of organic matter from a beverage industrial wastewater. Freundlich adsorption isotherm was used to analyze the adsorption efficiencies of the two activated carbons. These studies indicate that acid-activated coconut shell carbon had higher adsorption for organic matter expressed as chemical oxygen demand, (COD), than barium chloride-activated coconut shell carbon and Calgon carbon (F-300) at all carbon dosages used. Thus, the potential for using agricultural waste (coconut shell) that litter our environment may be valuable resources for removal of organic matter from industrial wastewater.

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O.S. Amuda

Papers

Removal of heavy metal from industrial wastewater using modified activated coconut shell carbon

Coagulation/flocculation process and sludge conditioning in beverage industrial wastewater treatment.

Coagulation/flocculation process in the treatment of abattoir wastewater

Performance optimization of coagulant/flocculant in the treatment of wastewater from a beverage industry

Industrial wastewater treatment using natural material as adsorbent