Papaya-clay combo could cut cost of water purification in developing countries

Jun 12, 2013
Papaya-clay combo could cut cost of water purification in developing countries

An inexpensive new material made of clay and papaya seeds removes harmful metals from water and could lower the cost of providing clean water to millions of people in the developing world, scientists are reporting. Their study on this "hybrid clay" appears in the journal ACS Sustainable Chemistry & Engineering.

Emmanuel Unuabonah and colleagues explain that almost 1 billion people in developing countries lack access to reliable supplies of for drinking, cooking and other key uses. One health problem resulting from that shortage involves exposure to heavy metals such as lead, cadmium and mercury, released from industrial sources into the water. Technology exists for removing those metals from drinking water, but often is too costly in developing countries. So these scientists looked for a more affordable and sustainable water treatment adsorbent.

They turned to two materials readily available in some . One was kaolinite clay, used to make ceramics, paint, paper and other products. The other: seeds of the Carica papaya fruit. Both had been used separately in water purification in the past, but until now, they had not been combined in what the scientists term "hybrid clay." Their documentation of the clay's effectiveness established that the material "has a strong potential for replacing commercial activated carbon in treatment of wastewater in the ."

Explore further: Nano-scientists develop new kind of portable water purification system

More information: "Hybrid Clay: A New Highly Efficient Adsorbent for Water Treatment" ACS Sustainable Chem. Eng., Article ASAP DOI: 10.1021/sc400051y

Abstract
New hybrid clay adsorbent based on kaolinite clay and Carica papaya seeds with improved cation exchange capacity (CEC), rate of heavy metal ion uptake, and adsorption capacity for heavy metal ions were prepared. The CEC of the new material is ca. 75 meq/100 g in spite of the unexpectedly low surface area (≈9 m2/g). Accordingly, the average particle size of the hybrid clay adsorbent decreased from over 200 to 100 μm. The hybrid clay adsorbent is a highly efficient adsorbent for heavy metals. With an initial metal concentration of 1 mg/L, the hybrid clay adsorbent reduces the Cd2+, Ni2+, and Pb2+ concentration in aqueous solution to ≤4, ≤7, and ≤20 μg/L, respectively, from the first minute to over 300 min using a fixed bed containing 2 g of adsorbent and a flow rate of ≈7 mL/min. These values are (with the exception of Pb2+) in line with the WHO permissible limits for heavy metal ions. In a cocktail solution of Cd2+, and Ni2+, the hybrid clay shows a reduced rate of uptake but an increased adsorption capacity. The CEC data suggest that the adsorption of Pb2+, Cd2+, and Ni2+ on the hybrid clay adsorbent is essentially due to ion exchange. This hybrid clay adsorbent is prepared from materials that are abundant and by a simple means that is sustainable, easily recovered from aqueous solution, nonbiodegradable (unlike numerous biosorbent), and easily regenerated and is a highly efficient alternative to activated carbon for water treatment.

add to favorites email to friend print save as pdf

Related Stories

Meeting the 'grand challenge' of a sustainable water supply

May 22, 2013

Scientists and engineers must join together in a major new effort to educate the public and decision makers on a crisis in providing Earth's people with clean water that looms ahead in the 21st century. That's the focus of ...

Clean drinking water for everyone

May 01, 2012

Nearly 80 percent of disease in developing countries is linked to bad water and sanitation. Now a scientist at Michigan Technological University has developed a simple, cheap way to make water safe to drink, even if it’s ...

Is enough being done to make drinking water safe?

May 30, 2013

There is a lack of evidence regarding the effectiveness of technologies used to reduce arsenic contamination finds research in BioMed Central's open access journal Environmental Evidence. More studies assessing the techno ...

Turning glass into clay

Jul 06, 2012

The magic mineral and microbial processes that transform volcanic glass into clay have been identified, adding important knowledge to how clay is formed.

Recommended for you

European climate at the +2 C global warming threshold

3 hours ago

A global warming of 2 C relative to pre-industrial climate has been considered as a threshold which society should endeavor to remain below, in order to limit the dangerous effects of anthropogenic climate change.

Australia's dirty secret: who's breathing toxic air?

5 hours ago

Australians living in poorer communities, with lower employment and education levels, as well as communities with a high proportion of Indigenous people, are significantly more likely to be exposed to high ...

Predicting bioavailable cadmium levels in soils

23 hours ago

New Zealand's pastoral landscapes are some of the loveliest in the world, but they also contain a hidden threat. Many of the country's pasture soils have become enriched in cadmium. Grasses take up this toxic heavy metal, ...

User comments : 0

More news stories

Melting during cooling period

(Phys.org) —A University of Maine research team says stratification of the North Atlantic Ocean contributed to summer warming and glacial melting in Scotland during the period recognized for abrupt cooling ...