Volume 40, Issue 6

In recent years, a significant increase in the amount of research published about the application of eggshells for the removal of metal ions from aqueous solutions has been observed. The paper presents different aspects of metal adsorption from aqueous solutions on untreated eggshells. Pretreatment procedures and tested parameters for the adsorption differ significantly across all the reviewed data, providing a source of variance for the results. For untreated eggshells, the range of the reported BET surface area is from 0.07 m 2 /g to 8.941 m 2 /g. Correlation between particle size and BET surface area has been highlighted. Reported removal efficiencies for the untreated eggshell have been compared. Reported results show that eggshell is most employed for the removal of Pb(II), Cd(II), and Cu(II) from aqueous solutions. Eggshell capacity to remove metal ions from the main group elements has also been demonstrated. While results look promising, not enough data are present to make reliable conclusions about its efficiency with other (mainly transition) metal ions – which makes it a possible research direction. Based on the reported data, multiple removal pathways are involved. Several eggshell modification methods and possibilities of creating new adsorbents using eggshells only as a part of the raw material have been assessed. Finally reported eggshell modification methods have been assessed and it is clear that to compare different material’s effectiveness as an adsorbent, comparing only materials adsorption capacities is insufficient. Certain environmental water pollution removal studies using adsorption demand further study, such as metal ion specification in aqueous solution, in different processing water, and even in wastewater.

Nutrient management methods based on ecosystems are crucial for providing agricultural nutrient needs while reducing the environmental impact of fertilizer usage. With increasing agricultural production, the global demand for potassium is increasing, with India importing potassium from countries like Canada, USA, Israel, and Russia. Biomass-fired industries generate biomass ash as a residue so management of the resultant ash is important. Agricultural residue ashes contain abundant potassium so could potentially be used for fertilizer application. This review describes different potassium sources and recovery processes, including chemical precipitation, water extraction, solvent extraction, membrane separation, and ionic exchange. Extraction time, temperature, and solid to solvent ratio affect the recovery of potassium from biomass ash. Water extraction is the most commonly used method for potassium recovery from biomass ash. The environmental impact of potassium fertilizer recovered from biomass ash is less than that of mining source of potash. This paper discusses topics not covered in previous reviews, such as different biosources of potassium, latest recovery methods, and life cycle assessment of these methods. The gaps identified in the reports are addressed, and future research opportunities are presented.

In the world’s rapidly expanding economy, textile industries are recognized as a substantial contributor to economic growth, but they are one of the most significant polluting industrial sectors. Dye-contaminated water sources can pose serious public health concerns, including toxicity, mutagenicity, and carcinogenicity among other adverse health effects. Despite a limited understanding of efficacious decolorization methodologies, the pursuit of a sustainable strategy for the treatment of a wide spectrum of dyes remains a formidable challenge. This article conducted an exhaustive review of extant literature pertaining to diverse physical, chemical, biological, and hybrid processes with the aim of ascertaining their efficacy. It also elucidates the advantages and disadvantages, cost considerations, as well as scalability impediments of the treatment methodologies, thereby facilitating the identification of optimal strategies for establishing techno-economically efficient processes in the sustainable handling of these effluents. The hybrid configuration exhibited superior efficiency and was documented to surmount the limitations and constraints inherent to individual techniques. The study also revealed that most of the proven and established dye removal techniques share a common limitation viz., the generation of secondary pollution (i.e., sludge generation, toxic intermediates, etc.) to the ecosystem.

Wax/paraffin deposition in production wells and oil pipelines is a major challenge for oil production. Extensive research has been conducted to improve understanding of this process. This paper presents a review of experimental work carried out with flow loops. Previous research investigated paraffin deposition process under the influences of temperature, flow rate/velocity, shear stress, water fraction, gas phase, pipe material, asphaltene concentration, and chemical inhibitors. Test results reveal that temperature and shear stress have significant impacts on wax deposition. Limited research has been conducted on wax deposition under multiphase flow. Even though more than 20 years of efforts have been spent on wax deposition studies, unfortunately we have not fully understood this phenomenon.