Volume 25 - 2023

The management of water pollution has been one of the main problems as people pay more and more attention in the current society to the preservation and repair of the natural environment. In this paper, natural montmorillonite was modified with starch as well as lanthanum chloride. The removal efficiency of various modified montmorillonites on pollutants was examined by simulating the water quality conditions of heavily polluted lake reservoirs in order to provide new eco-friendly and effective materials for the treatment of heavily polluted lakes and reservoirs. The experimental results showed that: The nitrogen removal rates of Na-Mont, St-Mont, La-Mont, St-La-Mont and La-St-Mont for 2 mg/L TN solution were 28.48%, 5.18%, 59.55%, 98.39%, 64.73%, respectively, and total phosphorus removal rates for 10 mg/L TP contaminated solution were 6.24%, 4.16%, 87.41%, 93.66%, 91.58% and for 100 mg/L COD solution the removal rates were 32.37%, 41.46%, 51.68%, 86.89%, 77.8%, respectively. By exploring the effect of La6-Mont adsorption for Cr6+ removal at different temperatures as well as reaction times, the results showed that the Cr6+ removal at saturation of La6-Mont adsorption was 76%, 80.5%, and 82.5% at the reaction temperatures of 15℃, 25℃, and 35℃, respectively. Among them, the removal rates of St-La-Mont reached more than 85%, 50% and 70% for COD, TN and for TP, respectively, and can be applied as fillers for enhanced artificial fast infiltration systems. The light rare earth composites La-St-Mont and LaCl3-Mont have achieved removal rates of 35%, 50% and more than 90% for COD, TN and for TP, respectively, and can be used as effective purification materials for treating water quality of heavily polluted lakes and reservoirs. Meanwhile, La6-Mont can effectively fix heavy metal ions and avoid the release of endogenous pollution in the bottom mud, which can be used as a material for the treatment of bottom mud in lake reservoirs. This shown that lanthanum, a light rare earth element, modified montmorillonite can not only remove a range of pollutants from water bodies but also has excellent removal rates. Additionally Besides, starch, lanthanum and montmorillonite are widely available materials with high economic benefits. Therefore, further studies on St-La-Mont, La-St-Mont, LaCl3-Mont and La6-Mont can provide new materials for the treatment of pollution in heavily polluted lakes and reservoirs.

This study analyses nighttime (7 p.m. to 6 a.m.) light pollution effects on ground-level ozone production in urban and sub-urban sites in Malaysia. In the absence of solar radiation, no photochemical reaction will occur during nighttime, resulting in zero readings of ground-level ozone (O3). O3 and nitrogen dioxide (NO2) data collected in 2020 were analysed to assess time series and diurnal variability at each site and between sites. The highest nighttime mean O3 concentration is Minden (60 ppb); meanwhile, for nighttime mean NO2 concentrations, the highest is Klang (43 ppb). The results show that sub-urban experienced higher O3 variations compared to urban areas. The monthly mean nighttime O3 and NO2 in urban and suburban areas display a gradual increase in O3 and NO2 variations from March to April, followed by a decreasing trend in the mid of the year. These variations in monthly air pollutants are related to the MCO, CMCO, and RMCO in Malaysia during 2020. Putrajaya (sub-urban site) was the darkest site (average lux: 20) for the whole dataset. In contrast, Minden (sub-urban site) was recorded as the brightest site with maximum light pollution (average lux: 70). The relationship between O3 and NO2 shows a negative correlation during nighttime for urban and suburban sites. Light pollution can reach levels that might affect nocturnal O3 and NO2 concentrations; therefore, the long-term variability of light pollution is essential for air pollution studies.

This goal of this study was to evaluate the effectiveness of a new coagulant extract from pumpkin seeds (PSC) for removing turbidity and organic compounds from different natural surface waters. Two design experiment methods, namely central composite design (CCD) and response surface methodology (RSM) were used to optimize PSC for removal of turbidity and organic matter via the chemical oxygen demand (COD) of surface water. The CCD results indicated that more than 74.7% of COD and 94.4% of nephelometric turbidity unit (NTUs) were removed under optimized conditions (pH = 7.4; mPSC = 1.5 g/L; time: 88 min). They allowed for final effluent with significantly higher quality in terms of organic content and safe to Vibrio fischeri to be obtained

Permanent damages and spalling occur in conventional concrete due to high temperatures. Also concrete loses its compressive strength amounting to about 50 to 75% of the original strength as reported in most of the research works. As opting for high grade of concrete leads to higher costs and emits CO2, an attempt to develop thermal-resistant geopolymer concrete is done. A new class of silica-alumina binders called geopolymers has the ability to withstand high temperatures. Generally geopolymer concrete (GPC) is having good strength and durability properties. In this paper, the heat resistance and strength performance of geopolymer is improved by adding aluminium oxide as an admixture in the doses of 1% and 2% by weight of rice husk ash. With rice husk ash, fine aggregate and coarse aggregate, thermally resistant GPC was created. As alkali activators, sodium hydroxide and silicate were employed. The molarity of NaOH solution was 12 and 14. The specimens were cast and oven-cured at 60°C for 24 hours. The specimens were tested to determine the strength, permeability, durability and thermal studies of geopolymer concrete.