Orange peels clean copper from water

When it comes to cheap organic materials for getting copper out of water, orange peels are quite appealing. But researchers need to make the peels more absorbent if they are to take on high levels of copper contamination such as those found in wastewater from Mexican mines, says Linda V. Gonzalez-Gutierrez of the Center for Research & Technological Development in Electrochemistry. Gonzalez-Gutierrez and her colleagues have tripled orange peels’ copper-absorbing abilities with help from a food-processing technique used to add texture to vegetables (Ind. Crops Prod. 2016, DOI: 10.1016/j.indcrop.2016.02.027). In this process, the researchers put millimeter-sized chunks of orange peels in a vacuum, spray them with pressurized steam, and then rapidly return the peels to a vacuum. Cycling this process pulls out any residual moisture from the peels and makes them puffier and more porous. The team further treats the peels to a citric acid bath, which populates their heightened surface area with carboxylic acid groups to snatch copper(II) out of solution. The porous peels could also take on organic contaminants in water. The modified peels are capable of absorbing nearly 15 times as much phenol as unmodified peels, the team reports.