Application of Carbon Nanotubes (CNTs) for Remediation of Emerging Pollutants - A Review

Nanotechnology is currently an upward trend in diverse fields, and therefore, its application will be reviewed in this paper. One of the nanotechnologies which can be used in environmental remediation is carbon nanotube (CNT). Its excellent mechanical and chemical properties allow it to have better achievement in remediating a wide range of organic and inorganic pollutants. CNT can be categorized into two types: single-walled carbon nanotube and multi-walled carbon nanotube. Due to urbanization, various types of pollutants have been released into the environment in great amounts. For instance, estrogen is the hormone generated and released from animals and humans. However, the overconcentration of estrogen affects the physiology of biological life. Besides, pesticides are frequently used by farmers to increase the fertility of the land for agricultural purposes, while heavy metals are commonly found during anthropogenic activities. Long-term absorption of heavy metals into the body tissues will accumulate toxic effects, leading to body system dysfunction. Hence, CNT technologies, including adsorption, membrane filtration, disinfection, hybrid catalysis, and sensing and monitoring, can be applied to remediate these pollutants. However, the application of nanotechnology and CNT faces several challenges, such as production costs, toxicity, ecological risks, and public acceptance. Application of CNT also has pros and cons, such that the lightweight of the CNT allows them to replace metallic wires, but dealing with nano-sized components makes it challenging.

Adsorption of Methylene Blue and Reactive Black 5 by Activated Carbon Derived from Tamarind Seeds

One of the most environmentally friendly methods to treat wastewater, especially synthetic dyes, is the production of activated carbon from agricultural waste. Tamarind seeds were transformed from negative-value waste into activated carbon in order to study the removal of synthetic dyes. The particular agro waste was soaked in ZnCl2 for chemical activation to increase its surface area and enhance its porosity. Physical activation of tamarind seeds was done by the carbonization process by burning at a temperature of 300 °C for 1 hour and cooling for 24 hours before washing with HCL to activate a pore surface for the tamarind seeds' carbon. The effects of parameters related to the adsorption of the dyes by tamarind seed activated carbon, such as contact time, initial concentration, absorbance dosage, and pH, were studied. The experimental data found that adsorption on both synthetic dyes exhibited a Langmuir isotherm in which the correlation value, R2, was 0.9227 (methylene blue) and 0.6117 (Reactive black 5). Meanwhile, the rate of adsorption for methylene blue (MB) and Reactive black 5 (RB5) by tamarind seed activated carbon was found to be well fitted in a pseudo-second-order model. More research is needed to meet the standard effluent of dyeing wastewater from the industrial sector.

Phenol Removal from Aqueous Solution by Adsorption Technique Using Coconut Shell Activated Carbon

Adsorption is one of the simplest techniques with low economic requirements. Coconut shell is an abundant agriculture waste which is inexpensive and easy to be obtained in Malaysia. This agriculture waste was transformed to activated carbon via 600°C of carbonization and zinc chloride activation. The ability of coconut shell-based activated carbon to remove phenolic compounds from aqueous solutions was evaluated. From the experiment, the equilibrium time for the adsorption of phenol onto coconut shell-based activated carbon is 120 minutes. The effect of the operating parameters, such as contact time, initial concentration, agitation speed, adsorbent dosage, and pH of the phenolic solution were studied. Adsorption kinetics models (pseudo-first-order, pseudo-second-order, and Elovich equation) and isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) were used to fit the experimental data.Pseudo-second-order was found to be the best fitted kinetics model to describe the adsorption of phenol on coconut shell-based activated carbon. While the equilibrium experiment data was well expressed by the Temkin isotherm model, The maximum adsorption capacity is determined as 19.02 mg/g, which is comparatively lower than the previous research. Meanwhile, 92% of removal efficiency was achieved by a dosage of 10g/L. Meanwhile, the adsorption of phenol by activated carbon was more favorable under acidic conditions. The favourable isotherm behavior was indicated by the dimensionless separation factor. The functional group and compound class of activated carbon before and after the experiment were determined through the analysis of Fourier-transform infrared (FTIR) spectroscopy.

A Study Case on Estimation of Soil Loss and Sediment Yield in Curtin University, Malaysia

Because of human activities, soil erosion has been one of the most concerning issues in Malaysia in the past decades. This study aimed to estimate the amount of soil loss and sediment yield at Curtin University, Malaysia by using the Revised Universal Soil Loss Equation (RUSLE) and the Modified Universal Soil Loss Equation (MUSLE), respectively. The parameters of RUSLE include rainfall erosivity factor (R), soil erodibility factor (K), slope length factor (L), slope steepness factor (S), cover-management factor (C) and support practice factor (P). The rainfall data (10 years) from the Sarawak Meteorological Department was used to determine the R-factor. The K-factor was determined by sieve analysis, hydrometer analysis, the Standard Proctor Test (SPT), and organic content testing. The L-and S-factors were performed by measuring on site and using Google Earth. The C-and P-factors were based on the ground surface cover condition (bare soil in this study). In the MUSLE, the runoff factor comprises V and Qp, while the other parameters are the same as in the RUSLE. The runoff depth, V, is equivalent to the rainfall intensity. Rainfall intensities were recorded by using a rain gauge. The highest rainfall intensity was used for runoff depth. The Rational method has been utilized to calculate Qp. The amount of soil loss estimated was 119.97 tons/ha/year and the sediment yield amount estimated was 0.76 ton/storm event in Curtin University, Malaysia.

Water Quality Assessment of Roof-collected Rainwater in Miri, Malaysia

Rainwater harvesting systems are becoming more acceptable as an alternative method to harvest water sources for both potable and non-potable uses. While the method has proven to be very simplistic and cost-effective, the collected rainwater source remains untreated and can pose serious health concerns if not used properly. This study focused on the physicochemical and heavy metal parameters of roof-collected rainwater in Miri, Sarawak. Individual sites were chosen throughout Miri, Sarawak for representative samples. Atomic Absorption Spectroscopy was used for the analysis of heavy metal concentrations. Heavy metal analysis included manganese, zinc, iron, copper, and cadmium. pH, temperature, turbidity, dissolved oxygen (DO), total suspended solids (TSS), total dissolved solids (TDS), nitrate, and fluoride were among the physicochemical parameters examined. Seasonal comparison indicated the majority of the higher concentration levels occurred during the wet season. The overall mean concentration for the physicochemical parameters indicated CLASS I usage, with the exception of BOD5, which was CLASS III usage. The overall mean concentration for metals analyzed indicated a CLASS I usage threshold with the exception of copper, which had concentrations well above the 0.02mg/L threshold for all sites. Thus, copper was considered one of the major contaminants for this study. Moreover, the types of storage tanks also showcased key findings. Open top storage tanks are more vulnerable to contamination than closed storage tanks. Metal storage tanks offer higher rainwater temperatures in comparison to other types of storage tanks.

Decolorization of Remazol Brilliant Violet 5R and Procion Red MX-5B by Trichoderma Species

Industrial wastewater including dye waste disposal, has been released in a massive amount and is difficult to degrade, especially synthetic dyes. In this study, 10 different types of fungi were isolated from a decayed wood in UTM forest and were labelled as S1-S10. Two dyes were chosen for this study, which were Procion Red MX-5B (PRMX5B) and Remazol Brilliant Violet 5R (RBV5R). These fungi were screened for their ability to decolor both dyes and further tested for their ability to decolor the dyes in liquid medium under several parameters; carbon and nitrogen sources, initial pH value, temperature, and agitation. S1 decolorized PRMX5B efficiently with the addition of glucose (45%), ammonium nitrate (61%), pH 3 (69%), temperature 37°C (49%), and agitation 100 rpm (69%), whereas S2 decolorized efficiently with the addition of glucose (60%), ammonium nitrate (49%), pH 3 (70%), temperature 37°C (46%), and agitation 100 rpm (74%). S1 demonstrated efficient decolorization of RBV5R with the addition of glucose (80%), ammonium nitrate (62%), pH 3, temperature 37°C (75%), and agitation 100 rpm (90%), whereas S2 demonstrated efficient decolorization with the addition of glucose (52%), ammonium nitrate (67%), pH 3, temperature 37°C (75%), and agitation 100 rpm (71%).The percentage of decolorization of dyes was measured by using a UV-Vis spectrophotometer. These fungi were then identified using the 18sr RNA method. Based on macroscopic and microscopic characteristics and a polygenetic tree, fungi S1 belong to Trichoderma koningiopsis and fungi S2 belong to Trichoderma atroviride.

Level and distribution of heavy metals in Miri River, Malaysia

Heavy metal pollution in water resources has become a serious and hazardous environmental problem all over the world because of its non-biodegradability, emanating from multiple sources, easy accumulation, and biological toxicity. This research was carried out to study the level and distribution of heavy metals at different sampling locations (upstream, midstream, and downstream), at different depths (0.5 m and 1.5 m from surface water level), and during low tide and high tide conditions in the Miri River of Miri City in Malaysia. The river water samples were collected and analyzed for Ca, Mg, Cu, Fe, Mn, Ni, Pb, and Zn by flame atomic absorption spectrophotometer. The concentration of Ca was found to be the highest in the Miri River, followed by Mg and Fe, and with traces of Cu, Mn, Ni, Pb, and Zn. An increase in the concentration of heavy metals, such as Cu, Mg, and Ni, was observed while flowing from upstream to downstream of the Miri River. Concentrations of heavy metals, such as Ca, Mg, Cu, and Zn, were clearly lower at 1.5 m depth than at 0.5 m depth. High tides in the river decrease the concentration of heavy metals, such as Ca, Cu, Mn, and Ni, compared to low tides. From this research, it gets clear that using the Miri River water for domestic and recreational purposes, washing, and fishing is detrimental to human health and the environment.

Interactions of Microplastics with Persistent Organic Pollutants and the Ecotoxicological Effects: A Review

With the increasing presence of microplastics and persistent organic pollutants (POPs), it is crucial to understand the interactions between the two emerging environmental pollutants and their ecotoxicological risks. This paper reviews more than 50 relevant scholarly papers published mainly in the past 10 years. It shows that the sorption of POPs to microplastics is affected by environmental factors and the properties of microplastics. The environmental factors comprise salinity, pH, natural organic matters and temperature. The properties of microplastics include degree of aging, molecular weight, size, shape, density, crystallinity, polymer type and color. The two factors are interconnected through weathering and weatherability of microplastics, where properties of microplastics, hence their interactions with POPs would be modified by environmental factors. Microplastics are potential vectors of POPs due to their ability to sorb and concentrate POPs. However, the studies reviewed showed the impacts to be low or insignificant and the sorbed POPs do not demonstrate significantly high accumulation, bioavailability and toxicity. In some literature, it has been reported that microplastics might reduce POPs in an organism. Due to limited studies and opposing views, there is a need to conduct more studies involving diverse POPs and microplastics under multiple conditions to provide a more holistic understanding on this subject.

Soil Remediation Applications of Nanotechnology

With the growth of urbanization, the anthropogenic activities have increased and thus increase occurrence of soil contaminants. In order to eliminate the contaminants in soil environment, the application of nanotechnology for soil remediation has become a great concern in the world. This review will discuss about the fate of contaminants in soil environment; the mechanisms of nanotechnology with various types of nanomaterials for the soil remediation; the advantages and disadvantage of nanomaterials towards the terrestrial organisms, human health as well as the soil environment; and the challenges of using nanotechnology for soil remediation.

Utilization Of Construction And Demolition Waster And Environmental Management Practice In South East Asian Countries

The ASEAN population will increase to 724.8 million by the year 2030 and the urbanization rate increases with years. This leads to the development of the construction industry to fulfil the fundamental social and physical requirements. Construction activities create an adverse negative impact on the environment, such as pollution and damage to the environment. This article will study more about the construction and demolition waste (C&D waste) and it can be founded in various construction stages. Therefore, the government and authorities introduce environmental management practices to mitigate the negative impact on construction on the environment and minimize the pollution at the source. What, why and where are terms required to consider before the implementation of environmental management practice. The government policies of Malaysia, Singapore and Thailand are summarized. Approximately 10% of total synthetic carbon dioxide (CO2) sourced from concrete production. The content more emphasizes the green materials generated from agricultural waste to replace the silica in concrete. The bamboo is used as interior decoration and material for building construction. Green materials technology is solar panel, solar thermal collector, geothermal technology, hydropower technology and cooling roof system.