article · Environment International
Groundwater contamination by toxic arsenic threatens drinking water supplies across the world. This pilot-scale evaluation tested agricultural and organic wastes, including egg shell, java plum seed, water chestnut shell, corn cob, tea waste, and pomegranate peel, to remove arsenate and arsenite from water. Among the tested materials, egg shell and java plum seed demonstrated the highest efficiency, removing 78 to 87 percent of arsenite at neutral pH, and 71 and 67 percent of arsenate under slightly acidic conditions. Maximum uptake occurred within two hours of contact time. Analysis indicated that hydroxyl, carboxyl, amine, and sulfur-bearing functional groups on rough, heterogeneous biosorbent surfaces enabled the binding of arsenic. Furthermore, both forms of arsenic could be desorbed up to 97 percent over four regeneration cycles, demonstrating reusable capacity for water treatment.
Arsenic in well water is a widespread, carcinogenic threat that affects millions of people. Conventional purification techniques can be unaffordable or inaccessible in low-resource areas. Demonstrating that everyday food waste materials like egg shells and fruit seeds can effectively capture and release toxic arsenic points the way towards low-cost, local solutions for safe community drinking water.
This work informs the development of low-cost, sustainable water filtration technologies targeting arsenic-affected communities and municipal or domestic water providers, particularly in developing regions. Because the research includes pilot-scale testing, contact-time dynamics, and multiple regeneration cycles, the concept sits at an applied testing stage, though engineering full filtration units and standardising sorbent preparation remain necessary steps before market deployment.
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Globally, contamination of groundwater with toxic arsenic (As) is an environmental and public health issue given to its carcinogenic properties, thereby threatening millions of people relying on drinking As-contaminated well water. Here, we explored the efficiency of various biosorbents (egg shell, java plum seed, water chestnut shell, corn cob, tea waste and pomegranate peel) for arsenate (As(V)) and arsenite (As(III)) removal from As-contaminated water. Significantly, egg shell and java plum seed displayed the greatest As(III) elimination (78-87%) at 7 pH followed by water chestnut shell (75%), corn cob (67%), tea waste (74%) and pomegranate peel (65%). In contrast, 71% and 67% of As(V) was removed at pH 4.1 and 5.3 by egg shell and java plum seed, respectively. The maximum As(V) and As(III) sorption by all the biosorbents was obtained, notably for egg shell and java plum seed, after 2 h contact time. Langmuir isotherm and pseudo-second order models best fitted the sorption data for both forms of As. The -OH, -COOH, -NH<sub>2</sub> and sulfur-bearing surface functional groups were possibly involved for As(III) and As(V) removal by biosorbents. The scanning electron microscopy combined with the energy dispersive X-ray spectroscopy (SEM-EDX) analysis showed that the heterogeneous surface of biosorbents, possessing rough and irregular areas, could have led to As sorption. Both As(V) and As(III) were successfully desorbed (up to 97%) from the biosorbents in four sorption/desorption (regeneration) cycles. This pilot-scale study highlights that egg shell and java plum seed have the greatest ability to remove both As species from As-contaminated drinking water. Importantly, these findings provide insights to develop an inexpensive, effective and sustainable filtration technology for the treatment of As in drinking water, particularly in developing countries like Pakistan.
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DOI: 10.1016/j.envint.2018.12.049
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