Enhanced photocatalytic disinfection of microorganisms

In this article, palladium modification and silver modification were used as examples to demonstrate the disinfection effects on microorganisms in aqueous environment of photocatalytic transition-metal-ion-modified nitrogen-doped titanium oxide (TiON/M) materials. Transition metal ion modification was applied to TiON to take advantage of the coupling between transition metal ion addition and TiON semiconductor matrix under visible light illumination. The coupling promotes the separation of electron and hole pairs produced by photon excitation, thus it could reduce the intrinsic charge carrier recombination from anion-doping, which largely limits the photoactivity of TiON under visible light illumination. Large enhancements on the hydroxyl radical production and the photocatalytic disinfection efficiency on microorganisms under visible light illumination were observed for TiON with both palladium and silver modifications. The superior photocatalytic performance under visible light illumination suggests that the transition metal ion modification is an effective approach to reduce the massive charge carrier recombination from anion-doping and to enhance the photocatalytic performance of anion-doped TiO2. The resulting photocatalytic materials have the potential for a wide range of environmental applications.

fulltext

P25-Graphene Composite as a High Performance Photocatalyst

Abstract

Herein we obtained a chemically bonded TiO2 (P25)-graphene nanocomposite photocatalyst with graphene oxide and P25, using a facile one-step hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide and loading of P25 were achieved. The as-prepared P25-graphene photocatalyst possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously, which was rarely reported in other TiO2−carbon photocatalysts. Hence, in the photodegradation of methylene blue, a significant enhancement in the reaction rate was observed with P25-graphene, compared to the bare P25 and P25-CNTs with the same carbon content. Overall, this work could provide new insights into the fabrication of a TiO2−carbon composite as high performance photocatalysts and facilitate their application in the environmental protection issues.

Particle length-dependent titanium dioxide nanomaterials’toxicity and bioactivity

Titanium dioxide (TiO2) nanomaterials have considerable beneficial applications varying from additives in paint, paper, plastics and cosmetics to uses in photocatalysts, solar cells and medical materials and devices. It has been established for many years that pigment-grade TiO2 (200 nm sphere) is relatively inert when internalized into a biological model system (in vivo or in vitro).

For this reason, TiO2 nanomaterials are an attractive alternative in applications where biological exposures will occur. Unfortunately, metal oxides on the nanoscale (one dimension <100 nm) may or may not exhibit the same toxic potential as the original material.

A further complicating issue is the effect of modifying or engineering of the nanomaterial to be structurally and geometrically different from the original material.

Results: TiO2 nanospheres, short (15 um) nanobelts were synthesized, characterized and tested for biological activity using primary murine alveolar macrophages and in vivo in mice. This study demonstrates that alteration of anatase TiO2 nanomaterial into a fibre structure of greater than 15 um creates a highly toxic particle and initiates an inflammatory response by alveolar macrophages.

These fibre-shaped nanomaterials induced inflammasome activation and release of inflammatory cytokines through a cathepsin B-mediated mechanism. Consequently, long TiO2 nanobelts interact with lung macrophages in a manner very similar to asbestos or silica.

Conclusions: These observations suggest that any modification of a nanomaterial, resulting in a wire, fibre, belt or tube, be tested for pathogenic potential.

As this study demonstrates, toxicity and pathogenic potential change dramatically as the shape of the material is altered into one that a phagocytic cell has difficulty processing resulting in lysosomal dysruptiion.

source

Nano-Based Sanitary Method Invented for Waste Water Treatment

TEHRAN (FNA)- Iranian researchers at Isfahan University came up with a type of nanoparticles that reduces the pollution caused by textile dyes through a relatively fast method.

“This research was based on nano-structural composite films of titanium dioxide, as a photocatalyst which is famous for its pollutant degradability characteristic,” Mojtaba Nasr Esfahani, the researcher in chief, told Iran Nanotechnology Initiative Council (INIC).

Noting that the main purpose of the research was to tackle waste water treatment and pollution related problems, Nasr Esfahani reiterated, “We exploited the photocatalytic behavior of titanium dioxide nanoparticles and by coating the particles into composite structure, it was practical to separate (or recover) catalyst from solution easily.”

In the research, three composite film types of titanium dioxide were prepared from different commercial titanium dioxide nanopowders. Stable suspensions of nanopowders with optimal molar ratios were dispersed in TiO2 cells and coated over glass slides.

The resulted composite films with specific concentration and acidity were ready to use after oxygen saturation process in exposure of UV irradiation.

Nasr Esfahani pointed out that the prepared composite films can be used to degrade some common textile synthetic dyes such as methyl orange, solophenyl red, light yellow (X6G), tertro direct light blue.

He referred to resolution of the problems concerning separation and filtration of titanium dioxide, and improvement of photocatalytic efficiency of the nanostructural composite films (with modified superficial characteristics) as advantages of the research work.

International effort to drain dangerous Bhutan lake underlines costs and risks of climate change

Thorthormi Tsho is a glacial lake perched precariously at 4428 metres above sea level in the remote Lunana area of northern Bhutan Rated as one of Bhutan’s likeliest future catastrophes, a breach and outburst flood through Thorthormi Tsho’s unstable moraine walls would most likely spill into the also vulnerable Raphsthreng Tsho 80 metres below, with the combined flood suddenly releasing up to 53 million cubic metres of water and debris into the upper catchment of the Po Chu river.

The first phase of an international project to reduce the risk to a Bhutan valley from the threatening bursting of a growing and increasingly unstable glacial lake is emphasising the huge costs of climate change adaptation in the Himalayas.

In a valley still bearing the scars of a just one third as large 1994 Glacial Lake Outburst Flood (GLOF) which took more than 20 lives and devastated villages and wrecked transport and power facilities, the prospect is frightening.

Rhino poaching surges in Asia, Africa

Rhino poaching worldwide is on the rise, according to a new report by TRAFFIC and the International Union for the Conservation of Nature (IUCN).

The trade is being driven by Asian demand for horns and is made worse by increasingly sophisticated poachers, who now are using veterinary drugs, poison, cross bows and high caliber weapons to kill rhinos, the report states.

Since 2006 the majority (95 percent) of the poaching in Africa has occurred in Zimbabwe and South Africa, according to new data.

“These two nations collectively form the epicentre of an unrelenting poaching crisis in southern Africa,” said Tom Milliken of TRAFFIC.

The report, which was submitted to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) ahead of its 15th meeting of the Conference of the Parties (CoP15) in March, documents a decline in law enforcement effectiveness and an increase in poaching intensity in Africa. The situation is most serious in Zimbabwe where rhino numbers are now declining and the conviction rate for rhino crimes in Zimbabwe is only three percent. Despite the introduction of a number of new measures, poaching and illicit horn trade in South Africa has also increased.

“Concerted action at the highest level is needed to stop this global crisis of rampant rhino poaching,” said Amanda Nickson, Director of the Species Programme at WWF International. “We call on the countries of concern to come to COP 15 in March with specific actions they have undertaken to show their commitment to stopping this poaching and protecting rhinos in the wild.”

The report also raises concerns regarding the low and declining numbers as well as the uncertain status of some of the Sumatran and Javan rhino populations in Malaysia, Indonesia and Vietnam.

“Sumatran and Javan rhino range countries need to increase efforts to better assess the current status of many of their rhino populations – to enhance field law enforcement efforts – prevent further encroachment and land transformation in rhino areas – and improve biological management of remaining rhinos to ensure the few remaining Sumatran and Javan Rhino numbers increase,” said Dr. Bibhab Kumar Talukdar, Chair of the IUCN/SSC Asian Rhino Specialist Group

Most rhino horns leaving southern Africa are destined for medicinal markets in southeast and east Asia, especially Vietnam, and also China. The report highlights Vietnam as a country of particular concern – noting that Vietnamese nationals operating in South Africa have recently been identified in rhino crime investigations. In addition, concern has been expressed about the status of Vietnam’s single Javan rhino population.

However, the report does note that in some areas populations of rhinos are increasing.

“Where there is political will, dedicated conservation programs and good law enforcement, rhino numbers have increased in both Africa and Asia,” said Dr Richard Emslie, Scientific Officer of IUCN’s African Rhino Specialist Group.

IUCN’s Rhino Specialist Groups and TRAFFIC were mandated to produce the report by CITES. The data collection and report writing for the report was partially funded by WWF and partners.

source: WWF

Cheap Dye sensitized Solar cells

Brazil sets example on halting forest loss

The recent announcement by Brazil – one of the world’s top emitters of greenhouse gases from deforestation – that it is adopting new emissions reduction targets could help steer negotiators in Copenhagen toward a stronger climate change deal.

Brazil’s top environment ministers said late last week the country is committing to an emission reduction target of between 36.1 and 38.9 percent by 2020. Brazil announced those figures only a day after saying new data showed the lowest deforestation rates in the Amazon in the past 21 years.

The new commitment can help unblock and steer climate negotiations toward a new global agreement in Copenhagen, which will be considered next month, said WWF-Brazil CEO Denise Hamú.

“As Brazil announces these figures, it moves from a situation where it merely holds developed countries to account to a situation where it can be a role model in the establishment of a new low-carbon development model for the world,” Hamú said.

“It should be noted, however, that the data needs to be more detailed,” she said. “We are not sure which baseline scenario was used, that is, how the Brazilian government estimated Brazil’s emission growth trends by the end of the next decade. Neither do we know how we will reach those targets.”

“No detailed information is available on all actions across the various industries and on our low-carbon plan of action. It is fundamental that all government policies be consistent with the announcement made today,” Hamú said.

As far as international climate negotiations are concerned, Brazil now has a more legitimate case to demand a clearer financial support commitment from the developed nations for the establishment of adequate actions to adapt to the effects of global warming, according to WWF.

Data released by the Brazilian government earlier this month showed that the deforestation rate in the Amazon fell between August 2008 and July 2009. Overall, the deforested region is a 45 percent smaller than Amazon land cleared the previous year, or between August 2007 and July 2008.

This is the lowest rate of deforestation in the Amazon since record-keeping began in 2000, and down from a high of more than 27,000 square kms in 2004.

However, deforestation also must be reduced in other damaged forest areas in Brazil, such as in the Cerrado, according to WWF:

Despite conservation efforts, global deforestation continues at an alarming rate – 13 million hectares per year, or 36 football fields a minute. It generates almost 20 per cent of global greenhouse gas emissions and halting forest loss has been identified as one of the most cost-effective ways to keep the world out of the danger zone of runaway climate change.

EU optimistic on climate deal after Brazil pledge

Brazil’s pledge to cut climate-warming emissions to 1994 levels over the next decade could help lead to a breakthrough at global climate talks next month, the head of the EU’s executive body said on Saturday.

“This is a potentially decisive step to achieve a global deal in Copenhagen in December and to succeed in the fight against climate change,” Jose Manuel Barroso, president of the European Commission, said.

The climate talks in Copenhagen aim to hammer out a new deal for battling global warming after the current Kyoto Protocol expires in 2012.

Brazil said on Friday it would take its emissions back to as low as 1994 levels of 1.7 billion tonnes — a cut of between 36.1 percent and 38.9 percent from projected 2020 levels.

Among the world’s biggest carbon polluters mostly due to deforestation, Brazil has become a major player in climate negotiations after years of rejecting such talks and saying the onus was entirely on rich countries to cut emissions.

Its gesture was seen as a possible way out of the deadlock in preparatory talks for Copenhagen that has arisen because rich countries have been slow to come forward with the billions of dollars needed to help poor nations tackle their rising emissions.

“All countries in the world have set December 2009 as a deadline for reaching an international agreement, and Brazil’s timing shows that this deadline works,” Danish climate minister Connie Hedegaard, whose country will host the negotiations, said in a statement.

“We are seeing more and more countries coming forward with climate plans.”

Many industrialized nations say they will not commit to handing funding to the developing world without getting concrete pledges of emissions cuts in return.

Alaska critical habitat for polar bear declared

In a move applauded by WWF, the US Department of the Interior has announced the proposed designation of almost 52 million hectares of key polar bear habitat across Alaska. The requirement for the identification of ‘critical habitat’ was triggered by the listing of polar bears as threatened under the US Endangered Species Act in 2008.

“Designation of critical habitat affords important protections to the polar bear, a species imperiled by dramatic changes in its sea ice environment,” says Geoff York, senior program officer for Polar Bear Conservation at WWF.

“As sea ice habitat shrinks, it becomes increasingly important to protect areas that are crucial for the bears’ survival.”

The critical habitat proposal announced today identifies habitat in three separate areas or units: barrier island habitat, sea ice habitat and terrestrial denning habitat. The total area proposed for designation would cover almost 52 million hectares (200,541 square miles).

Barrier island habitat includes coastal barrier islands and spits along Alaska’s coast, and is used for denning, refuge from human disturbances, access to maternal dens and feeding habitat, as well as travel along the coast. Sea ice habitat is located over the continental shelf, and includes water 300m and less in depth. Terrestrial denning habitat includes lands within 32 km (about 20 miles) of the northern coast of Alaska between the Canadian border and the Kavik River and within 8 km (about 5 miles) between the Kavik River and Barrow.

WWF works around the Arctic with local communities, scientists and governments to enhance polar bear conservation, protect their habitat, and ensure sustainable populations. WWF encourages the Department of the Interior to ensure that the views of local people are incorporated in the designation of critical habitat areas.

The world’s top scientific experts on polar bears, the Polar Bear Specialist Group of the International Union for the Conservation of Nature (IUCN), recently concluded that the IUCN Red List classification of the polar bear should be upgraded from ‘Least Concern’ to ‘Vulnerable’. That was based on the likelihood of an overall decline in the size of the total population of more than 30% within the next 35 to 50 years.. The principal cause of this decline is climatic warming as it melts away the polar bears’ important sea ice habitat.

At the Polar Bear Specialist Group Meeting this summer, the experts concluded that eight polar bear population groups are now in decline, up from five in 2005.

“Polar bears are not land animals – they evolved over thousands of years to be sea ice specialists. They need the ice to hunt for seals, their primary food. Take away the ice and you take away the bears,” added York.

In recent years, science has documented a decline in the condition and cub survival rate of some of the most southerly bear populations, and most recently significant increases in polar bear movements and home ranges as animals are forced to migrate longer distances in search of food or habitat.

“The changes we are witnessing in the Arctic do not just raise concerns about the fate of iconic species such as polar bear – our own future is at stake,” said York.

“The planet is changing in dangerous ways and the longer we wait to address the climate crisis the costlier it will be. While designation of critical habitat for polar bear is a positive step, it remains critical that the U.S. Senate pass a climate bill this year, moving us closer to reaching a global agreement in Copenhagen this December.”

Source:wwf