Resource World Magazine

o c t o b e r / n o v e m b e r 2 0 1 6 www.resourceworld.com 61 grEEN TECHNOlOgiES renewable energy by the end of 2018. Lens Technology is the first of Apple's partners to make such a move in line with Apple's sup- ply chain clean energy program. Apple's initiatives are not only intended to reduce its own environmental footprint, but also to help toward cleaning the envi- ronmental landscape in China, which for so long has been ignored by big-name companies in favour of cheap labour and low manu- facturing costs. Apple is working with its suppliers in China, and also announced that all 14 of its final assembly sites in China are now compliant with UL's Zero Waste to Landfill validation, which certifies that all waste is reused, recycled, composted, or, when nec- essary, converted into energy. "We want to show the world that you can manufacture responsibly and we're working alongside our suppliers to help them lower their environmental impact in China," said Lisa Jackson, Apple's vice president of Environment, Policy and Social Initiatives. "Our power purchase agreement is the first of its kind in southern China and we hope it will serve as an example for other companies looking to transition to cleaner, more economical sources of power," added Lens CEO, Zhou Qunfei. "We're pleased to be the first supplier to commit to covering all of our Apple pro- duction with renewable energy, and proud to source from local Hunan wind farms to power our facilities in Changsha." solar dEvicE disinfEcts watEr A tiny device, half the size of a postage stamp, which can rapidly disinfect water with solar energy has been developed by research- ers at Stanford University and the SLAC National Accelerator Laboratory. The nanostructured device has been tested with small amounts of water, and on three strains of bacteria, and shows promise in the search for affordable and effective low-power water purification solutions. We already use the sun's energy to disinfect and purify water, such as with solar stills or through passive solar UV disinfection (exposing the water to the sun's rays for up to 48 hours), but con- sidering the severe health threats that contaminated water poses to many people, there's always room for more options. And this gadget, because it's small and made from inexpensive and easy to make material, molybdenum disulfide, could eventually be a viable solution for point-of-use water disinfection, either in the developing world or for emergency situations. According to the researchers' findings, which were published in Nature Nanotechnology under the title "Rapid water disinfection using vertically aligned MoS 2 nanofilms and visible light," the tiny device killed "more than 99.999% of bacteria in just 20 min- utes" through the actions of its molybdenum disulfide nanoflakes (very thin films stacked on edge on a glass substrate). Molybdenum disulfide is an industrial lubricant, but, it takes on entirely different properties when made in layers a few atoms thick. In this case it becomes a photocatalyst: when hit by incom- ing light, many of its electrons leave their usual places, and both the electrons and the "holes" they leave behind are eager to take part in chemical reactions. "By making their molybdenum disulfide walls in just the right thickness, the scientists got them to absorb the full range of visible sunlight. And by topping each tiny wall with a thin layer of copper, which also acts as a catalyst, they were able to use that sunlight to trigger exactly the reactions they wanted – reactions that produce "reactive oxygen species" like hydrogen peroxide, a commonly used disinfectant, which kill bacteria in the surrounding water," according to Chong Liu, lead author of the report. The killer chemicals quickly dissipate, leaving behind just potable drinking water. However, because the device hasn't been tested with other bacterial strains, under real world conditions with the "complex stews of contaminants" found there, and doesn't remove chemical pollutants from water, it's not a one-size- fits-all purification device, but could lead to further innovations in water disinfecting. n a researcher holds a small, nanostructured device that uses sunlight to disinfect water. By harnessing a broad spectrum of sunlight, it works faster than devices that use only ultraviolet rays. (Jin Xie/ Stanford University)

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