Phytomining of precious metals from mine wastes

The increasing demand for precious metals such as palladium and gold for industrial applications has led to the exploration of sustainable environmental-friendly technologies to capture and recycle these metals from mine wastes. Phytomining is an emerging technology that makes use of the ability of plants to extract and accumulate metals from soil and water. Chapter 3 discusses the potential of phytomining to recover palladium from mine waste materials. These studies determined that willow (Salix sp.) and miscanthus (Miscanthus giganteus) were able to accumulate high levels of palladium in the aerial tissues when grown on synthetic media containing palladium as well as on mine waste materials. The use of chemical lixiviants improved the uptake and translocation of palladium in both willow and miscanthus. The potential of palladium nanoparticle formation in plants as plant-based catalysts was investigated but no palladium nanoparticles were detected when the plants were grown on synthetic mine waste. Chapter 4 evaluates the potential of merA gene for mercuric reductase in Arabidopsis as a genetic engineering approach to improve tolerance to gold and palladium in plants. In contrast to previously published findings merA expression did not increase tolerance of the transgenic plants to toxic levels of gold and palladium. Inhibition studies on purified mercuric reductase further revealed that gold and palladium inhibited the activity of MerA with ionic mercury. In Chapter 5, the potential of synthetic biology strategy was also investigated where the expression of synthetic short peptides, which are shown to be responsible in the formation of various sizes of metal nanoparticles in vitro, were found to increase the formation of smaller sized gold nanoparticles (<10 nm diameter) compared to wild type plants when expressed in Arabidopsis. Chapter 6 describes the transcriptional response of Arabidopsis to precious metals and investigates the potential involvement of heavy metal transporter 5 (AtHMA5) in the detoxification mechanism for gold and palladium. AtHMA5 was found to be strongly up regulated in response to gold and palladium. However, studies with Arabidopsis hma5-1 mutant knockout lines and yeast heterologous expression studies demonstrated that gold and palladium is not a substrate for AtHMA5 suggesting that AtHMA5 is not involved in gold and palladium detoxification. Overall, this work is the first to describe a holistic approach in searching for suitable field applicable plant candidates for phytomining of precious metals such as palladium and gold as well as strategies to improve its uptake, tolerance and nanoparticle formation in plants

Indeed money (gold) grows on trees

Recent Kim Kim River toxic pollution incident has raised eyebrows and sparked anger of Malaysian public about the irresponsible act of water pollution. Although this is an extreme pollution case of toxic proportion, day-to-day mining activities will leave behind mine wastes which may contain toxic chemicals such as arsenic that might be leached out during the refining process. Scientists are now using plants to remediate this hidden threat, and literally turning mine tailings into gold nanoparticles for industrial use. The Petri Dish (PD), guest writer, SHAWN KENG interviewed International Islamic University Malaysia’s Dr Zakuan Azizi Shamsul Harumain (ZA) – to explain what phytomining and phytoremediation are, and its promising “Midas Touch” potential in turning mine tailings into mine treasures

Biodegradation of Petroleum Sludge by Methylobacterium sp. Strain ZASH

A bacterium was isolated from sludge-contaminated soil in a petroleum refinery and tested for its ability to degrade aliphatic hydrocarbon compounds present in petroleum sludge. The isolate was grown on minimal salt media agar supplemented with 1 % (w/v) petroleum sludge. The isolate was tentatively identified as Methylobacterium sp. strain ZASH based on the partial 16s rDNA molecular phylogeny. The bacterium grew optimally between the temperatures of 30 °C and 35 °C, pH 7 and 7.5, 0.5 and 1.5 % (v/v) Tween 80 as the surfactant, and between 1 and 2 % (w/v) peptone as the nitrogen source. The constants derived from the Haldane equation were ?max = 0.039 hr-1, Ks = 0.385 % (w/v) total petroleum hydrocarbons (TPH) or 3,850 mgl-1 TPH, and Ki =1.12 % (w/v) TPH or 11,200 mgl-1. The maximum biodegradation rate exhibited by this strain was 19 mg l-1 hr-1 at an initial TPH concentration of 10,000 mg l-1. Gas chromatography analysis revealed that after 15 days the strain was able to degrade all aliphatic n-alkanes investigated with different efficiencies. Shorter n-alkanes were generally degraded more rapidly than longer n-alkanes with 90% removal for C-12 compared to only 30% removal for C-36. The addition of sawdust did not improve bacterial degradation of petroleum hydrocarbons, but it assisted in the removal of remaining undegraded hydrocarbons through adsorption

Evaluation of occupational exposure to TiO2 nanoparticles: microwave-assisted acid digestion method on air membrane filters

Titanium dioxide (TiO2) nanoparticles have been extensively used in various industrial sectors and applications, including cosmetics, catalysts, food additives, inks, paints, and coatings. However, the International Agency for Research on Cancer (IARC) has classified TiO2 nanoparticles as a potential carcinogen for humans, meaning they may cause cancer and pose serious health complications, particularly for manufacturing workers. This highlights the need for better evaluation to determine worker exposure. In this study, suspended TiO2 nanoparticles were sampled using a nanoparticle respiratory deposition (NRD) sampler fitted with specially designed membrane filters and analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The digestion method used for titanium element recovery after nanoparticle sampling is crucial for optimal ICP-MS analysis. Therefore, this study aimed to investigate the most suitable digestion method. A microwave-acid digestion method using concentrated nitric acid and concentrated hydrochloric acid at a 7:4 ratio, with a run time of 30 minutes and the temperature set to 200°C showed remarkable titanium recovery compared to other methods. These findings may pave the way for optimal analysis of suspended TiO2 nanoparticles in assessing occupational exposure while promoting sustainability and eco-friendliness in resource utilization

The potential of silica from rice husk ash on removal of sulphide in wastewater

The production of propylene from propane dehydrogenation process in the petrochemical sector regularly produce high concentration of sulphur in the form of sodium sulphide (Na2S). High concentration of sulphide can lead to corrosion in sewage pipes, massive fish kill and obnoxious odors into the atmosphere. Adsorption technique using lowcost and environmentally friendly adsorbents derived from natural resources such as rice husk ash (RHA) may offer a suitable alternative for in situ removal of contaminants such as sodium sulphide in industrial wastewater. In this work, the use of silica synthesized from RHA was investigated for its potential in removing high concentration of sulphide (S2-) in the form of sodium sulphide from wastewater. Results showed that pure silica with the size around 0.9 to 2.0 μm was successfully synthesized from RHA. Significant reduction of sulphide level was observed after being treated with RHA based silica calcined with clay compared to other adsorbents such as chemically treated nanoporous zeolite and natural clay itself with more than 90 % removal after 120 minutes of treatment with the value of the pseudo-first-order rate constant, k of 0.1404, 0.14 and 0.1519 for silica compared to zeolite. This suggests that the use of silica derived from RHA has a potential to be used as sulphide remover in industrial wastewater without extensive chemical treatment to improve its removal capacity

Towards developing methods to increase uptake of palladium by plants for revegetation and remediation of mine wastes

Waste materials (tailings) generated from mining processes contain significant amounts of palladium, which are considered uneconomical to be extracted using conventional methods. Studies have demonstrated that Arabidopsis thaliana (Arabidopsis) can accumulate palladium as nanoparticles in the plant tissues. In collaboration with the Green Chemistry Centre of Excellence at the University of York, we have recently demonstrated that this nanoparticle rich material can be used as a high-value catalyst, without the need to extract the metals from the plant biomass [1]. One of the properties of palladium is that it occurs naturally in the zero valent form. This represents a problem for phytoextraction as transition metals are usually taken up by plants as cations. To overcome this problem phytoextraction of gold, which is chemically similar to palladium, uses cyanide-based methods to promote gold solubility in soil. The use of cyanogenic compounds is not a long-term, environmentally sustainable method for palladium phytoextraction. Alternative methods may come from a greater understanding of the biological processes involved. Our studies have identified genes that are strongly regulated by gold, including a discreet suite of divalent metal cations [2]. We are now extrapolating these investigations to palladium to investigate solubilisation, uptake and nanoparticle formation of palladium in plants. [1] Parker et al. (2014). PLoS One 9:e87192 [2] Taylor et al (2014). PLoS One 9:e9379

Biodegradation of petroleum sludge by Methylobacterium sp

A bacterium was isolated from sludge contaminated soil in petroleum refinery centre and tested for its ability to degrade hydrocarbon in petroleum sludge obtained from Shell Refinery Centre, Port Dickson, Negeri Sembilan. The isolate was tentatively identified as Methylobacterium sp. strain ZASH based on the partial 16s rRNA molecular phylogeny. The optimum condition for the strain to degrade petroleum sludge was characterized and quantified using GCFID. It was revealed that the bacterium degrade optimally between the temperature of 30°C to 35°C, pH 7 to 7.5, 0.5 to 1.5% (v/v) Tween 80 as surfactant source and at 1 to 2% (w/v) peptone as the nitrogen source. Gas chromatography analysis revealed that after 15 days, the Methylobacterium sp. strain ZASH was able to degrade 70% of hydrocarbons component of chain length C12-C36 found in petroleum sludge. It was also found that sawdust can be a good hydrocarbon adsorbent as its addition increase the hydrocarbon removal up to 99% removal

R&D to commercialization – nanotechnology

The reciprocal relationship between research development (R&D) and commercialization lies on its ability to compensate the needs of both parties. In today’s world, without having a strong commercialization aspect, millions of dollars spent on R&D would be pointless and futile. Nanotechnology is a continuation of R&D in advance technology that deals with nanoscale materials which has a strong potential in transforming economies and societies on a global scale. This fast emerging technology has already booked its place in the industry such as the production of graphene, a single-layer man-made material which has 200x more strength than normal steel and possess high conductive capacity important in the electronics sector. In NanoMalaysia Berhad, we champion nanotechnology’s R&D and commercialization as a single entity by bringing potential research products from academia or research institute into market by either by forming new companies or joint ventures with local or international collaborators. This will not just benefit the government’s economic growth in a long run, but will also help in creating more alternative career opportunities as an industrialist equipped with research degrees

Malaysia’s graphene commercialization progress National Graphene Action Plan 2020

NanoMalaysia’s National Graphene Action Plan 2020 is supported by the country’s 11th Malaysia Plan (2016- 2020) as a catalytic support to expedite industrial adoption of graphene applications. Realizing the economic significance in the global market, more than 30 product development and pilot production projects have been initiated in the form of – government-industry-academia partnerships. These graphene based products are at the cusp of entering mainstream local and global markets

The potential of agro based nanomaterials for nanofilters to capture suspended titanium nanoparticles in the air

Nanomaterials have a wide range of new technologies and industrial use and have created many new products and employment opportunities. However, they can also pose unknown risks and specific uncertainties in occupational safety and health issues. The latest and most worrying issue involves the increasing production and nanoparticles, particularly titanium dioxide (TiO2). Therefore, a rigorous study should be carried out to obtain more intensive information to develop a new technique for personal exposure monitoring. The commercially available nanoparticle respiratory deposition (NRD) sampler usually occupied with nylon filter contains TiO2 background material and is rather expensive. As an alternative, agro based nanofilters were developed from nanomaterials synthesized from rice husks, namely, nanosilica and nanozeolite embedded on/in a polyvinylidene fluoride (PVDF) membrane. As a comparison, graphene was also used to produce nanofilters due to its outstanding performance in chemical absorption. Analysis using Field Emission Scanning Electron Microscope (FESEM) showed a formation of cracks on both nanofilters when embedded with 1% w/v of either nanosilica and nanozeolite compared to 0.1 and 0.5 % w/v. Agglomerate of nanosilica particles with the size between 20 – 40 nm and nanozeolite with the size between 18 – 30 nm were identified on the developed nanofilter. Energy Dispersive X-ray (EDX) confirmed the presence of functional groups such as silica, oxide, sodium, alumina, and carbon on the developed nanofilters, further confirming the deposition of the nanomaterials on the PVDF membrane. Further investigation on the ability to capture titanium nanoparticles using 0.1 % w/v nanofilters from both materials showed that all filters tested could capture titanium nanoparticles with nanozeolite filters showing the highest accumulation with 9170 mg/m3. These results suggest that agro-based nanomaterials can be used as nanofilters to capture titanium nanoparticles in the air