Utilization of agricultural waste adsorbent for the removal of lead ions from aqueous solutions

In this study, a performance evaluation of an aluminium oxide modified onion skin waste (Al2O3/OSW) for the removal of heavy metal ions (Pb2+ and Cd2+) from aqueous solution was investigated under batch mode adsorption. The surface morphology, elemental composition, functional groups, textural characteristics and surface charge of the as-made Al2O3/OSW adsorbent were examined using SEM, EDX, FTIR, BET surface area and pHpzc techniques, respectively. The effects of initial cations concentration, contact time, adsorbent dosage, and pH on adsorption of Pb2+ and Cd2+ onto Al2O3/OSW were studied. The adsorption data obtained were evaluated by various adsorption isotherm and kinetic models. Results obtained showed that maximum removal percentages of Pb2+ and Cd2+ were 91.23 and 94.10%, respectively, at the optimum Al2O3/OSW dosage of 1.4 g, contact time of 180 min and aqueous solution pH of 6.0. The isotherm and kinetic studies showed a multilayer adsorbate-adsorbent system with the dominance of the chemisorption mechanism. The study concluded that onion skin waste is a viable, cheap and very effective alternative for removing heavy metal ions from water/wastewater.

Onion (Allium Cepa) Processing Waste as a Sorption Material for Removing Pollutants from Aqueous Media

The paper summarizes the literature data on the use of onion (Allium cepa) processing waste as sorption materials to remove various pollutants (metal ions, dyes, antibiotics) from aqueous media. It provides brief literature data on the structure, volume of cultivation, and chemical composition of some components of onion biomass. It was found that onions contain many amino acids, vitamins, polyphenolic compounds, and other biologically active compounds that have various functional groups in their composition. This contributes to the removal of various metal ions (Ca2+, Cd2+, Cr(VI), Cu2+, Hg2+, Mg2+, Ni2+, Pb2+, Zn2+) from aqueous media with native and modified onion processing waste (onion skin). The work shows the possibility of increasing the sorption characteristics of pollutants by treating the Allium cepa biomass with various chemical reagents. It was found that the pollutant adsorption isotherms on onion skin are most often more accurately described by the Langmuir and Freundlich models, less often by other models. The kinetics of the process predominantly corresponds to the pseudo-second-order model. It was shown that the use of onion skin extracts modified with various chemical compounds is promising for removing heavy metal ions. The work also shows the possibility of using onion skin modified by plasma and microwave radiation to remove the Methylene blue dye from simulated solutions.

Physicochemical and Thermal Characteristics of Onion Skin from Fifteen Indian Cultivars for Possible Food Applications

Every year tons of onion waste is produced worldwide. The dried outer onion skin contributed up to 70% of this waste. Outer-dried skins of fifteen prominent onion cultivars from India were selected for the study. A comparative study was done for proximate profiling, thermal characteristics, functional grouping, and mineral contents. Skin of cv. “NHRDF Red” contained the highest amount of crude protein (5.97 ± 0.15 g/100 g), ash (12.24 ± 0.59 g/100 g), and fiber (8.28 ± 0.20 g/100 g), whereas cv. “Pusa Red” possessed the highest amount of total fat (0.47 ± 0.02 g/100 g) and the maximum carbohydrates (76.66 ± 0.56 g/100 g) were found in “Pusa Riddhi.” Mineral analysis showed that cv. “NHRDF Red” had the maximum concentration of all 9 minerals along with sulphur content. Fourier transform infrared spectroscopy analysis explored the various metabolites present in each cultivar. The thermal analysis explored cv. “Agri Found Dark Red” as highly thermally stable having 70.98% residual mass. The lowest Tg temperature range was found between 64.4°C and 90.6°C for “Agri Found Dark Red.” Skin of cv. “NHRDF Red” was reported as the best source of protein, fiber, and minerals, which may be utilized for developing a food product.

Wastewater Washing Rice With Onion Skin On Growth And Production Of Chillian Plants

Cayenne pepper (C frutescent L.) is one of the leading horticultural commodities in general. Chili fruit also contains many nutrients that are needed for human health including protein, fat, carbohydrates, calcium (Ca), phosphorus (P), iron (Fe), vitamins and contain alkaloid compounds such as capsicum, flavonoids, and essential oils (Adhi Santika, 1996). One type of fertilizer that is known to increase soil nutrients is organic fertilizer. Organic fertilizer in liquid form is one type of fertilizer that can be an option, in addition to facilitating the absorption of nutrients. Based on the results of laboratory analysis, it is known that the nutrient content contained in liquid organic fertilizer of rice washing water with onion skin does not meet the minimum technical standards under the Regulation of the Minister of Agriculture No. 70 of 2011 concerning organic fertilizers, biological fertilizers, and soil enhancers. Along with the results of the laboratory analysis, the POC of rice washing water with onion skin did not have a significant effect on the vegetative growth of cayenne pepper with concentrations of 50 and 75%.