The characteristics of aerogel materials such as the low density and large surface area enable them to adsorb large amounts of substances, so they show great potential for application in industrial wastewater treatment. Herein, using a combination of completely environmentally friendly materials such as cellulose nanofibers (CNFs) extracted from the petioles of the nipa palm tree and graphene oxide (GO) fabricated by simple solvent evaporation, a composite aerogel was prepared by a freeze-drying method. The obtained aerogel possessed a light density of 0.0264 g/cm 3 and a porosity of more than 98.2%. It was able to withstand a weight as much as 2500 times with the maximum force (1479.5 N) to break up 0.2 g of an aerogel by compression strength testing and was stable in the aquatic environment, enabling it to be reused five times with an adsorption capacity over 90%. The CNF/GO aerogel can recover higher than 85% after 30 consecutive compression recovery cycles, which is convenient for the reusability of this material in wastewater treatments. The obtained aerogel also showed a good interaction between the component phases, a high thermal stability, a 3D network structure combined with thin walls and pores with a large specific surface area. In addition, the aerogel also exhibited a fast adsorption rate for methylene blue (MB) adsorption, a type of waste from the textile industry that pollutes water sources, and it can adsorb more than 99% MB in water in less than 20 min. The excellent adsorption of MB onto the CNF/GO aerogel was driven by electrostatic interactions, which agreed with the pseudo-second-order kinetic model with a correlation coefficient R 2 = 0.9978. The initial results show that the CNF/GO aerogel is a highly durable “green” light material that might be applied in the treatment of domestic organic waste water and is completely recoverable and reusable.
Groundwater is an important resource of provinces in Ca Mau Peninsula. The water is supplied to household, industrial, agricultural and aquacultural activities. More important, in this area, as the majority of surface water is contaminated and requires further treatment to become usable, the main source of water supply is the groundwater. Under the impacts of socialeconomic development, the increase of population and the urbanization rate in the region, groundwater resource is under a pressure of exploitation and utilization. Yearly exploited amount of groundwater is larger than the replenishment amount in most aquifers, so the groundwater level is lowered gradually year by year. According to statistics from 2000 to 2010, the groundwater level has been lowered from 0 to -14m (in some places, the water level is lowered to -28m below sea level) in qp2-3 and qp1 aquifers, with the highest drops in Bac Lieu and Soc Trang provinces. The amount of pumped groundwater in the region has been increasing from 159.914 to 931.944 m3 / day, whereas the replenishment amount has been decreasing from 526.121 to 185.004 m3 / day. Stated otherwise, groundwater in the region is declining in both volume and quality under the impact of climate change and exploitation activities. This paper uses the DPSIR framework to assess causal relationships of factors that impact to the groundwater environment in the region, and thereby propose appropriate solutions under the impacts. In combination with groundwater environmental indicators to quantify the degradation impacts to groundwater resource, the results of this paper indicate that water supply used mainly in Ca Mau Peninsula is groundwater ( 85.74%); the capacity of renewable water per capita in the region is still very low (80.06 l / day / person); the water loss from aquifer systems is much larger than the amount of replenishment (141.02%), however the amount of water extraction for domestic service was still in permissible limits of the aquifers (8.71%). The numbers show that groundwater in Ca Mau Peninsula is in decline but still within safe limits. Results from this paper can give authorities a more intuitive view about the current situation of groundwater when planning and using water resources.
This paper reveals the capacity of supplement for groundwater by rainfall resource based on the monitoring and analyzing result of rainfall, evaporate, groundwater table of central-collecting well and monitoring wells as well as the geophysical test result in dormitory area of VNU-HCM from November 2007 to February 2009.
In Ca Mau peninsula region, groundwater resource is the main source of water supply for agriculture, industry, domestic uses. In this paper, the authors study groundwater origin in middle - upper pleistocene (qp2-3) aquifer in Ca Mau peninsula and give some opinions about the groundwater origin formation for planning and managing reasonable, safe, and sustainable. There are many studies about groundwater origin in the Mekong delta plains and these studies showed different results. Up till now, there is not a consensus on an exact origin of groundwater in Mekong delta plains, especially in Ca Mau peninsula. Therefore, the authors use the Xulin approach to determine groundwater origin based on the concentration of ions Na+, Cl-, SO42-, Mg2+. Then we use Piper diagram, Gibbs plot, Mercado plot, and hydro-geochemical section plot to explain the origin of groundwater in Ca Mau peninsula region. The results show that there are 4 types of groundwater origin in the studied region: magnesium – chloride, marine origin; calcium – chloride, deep metamorphic environment; sodium – sulfate, the continental leaching origin; bicacbonnat-sodium, continental environment. The groundwater origins relate to the marine transgression and regression process, or weathering, leaching, and freshwash processes. The groundwater origin formation do not have participation of rainfall water and river water, which are two important components contribute to the groundwater recharge formation. Therefore, researching groundwater recharge of th e qp2-3 aquifer in the Ca Mau peninsula is according to other aspects.
It is indicated from the research results that the middle-upper Pleistocene aquifer (qp2-3) in Ca Mau peninsula region has the groundwater source which is formed including static reserves, marginal penetration reserves, and other aquifer penetration reserves, in which the static reserves ranges greatly. The unreasonable exploitation of groundwater with a great number of wells in the qp2-3 aquifer exceeded the limit reserve, as a result, the annual lowering of the groundwater level is very high, and other sustainable values of this aquifer exceeded the limits many times. From the research, it is very necessary to collaborate between the local governments in managing and exploiting the groundwater resource. And the urgent solution is to select the exploitation areas, to balance the reasonable number of wells, and to manage the exploitation volume. Another solution is to research the exploitation capacities of deeper aquifers, and to have an effective plan of using rainwater and surface water resources in parallel.
Đánh giá sự tổn thương do tác động xâm nhập mặn đến tầng chứa nước pleistocene giữa -trên (qp 2-3 ) vùng bán đảo Cà Mau Đào Hồng Hải, Nguyễn Đình Tứ Tóm tắt-Tác động của biến đổi khí hậu (BĐKH) và hoạt động khai thác quá mức đang làm suy giảm chất lượng và trữ lượng nước dưới đất khu vực bán đảo Cà Mau. Nghiên cứu này sử dụng chuỗi chỉ số GALDIT đánh giá khả năng tổn thương nguồn tài nguyên nước dưới đất do xâm nhập mặn dưới tác động của hoạt động khai thác và mực nước biển dâng. Kết quả phân vùng theo chỉ số GALDIT cho thấy sự tổn thương do tác động của xâm nhập mặn của tầng chứa nước Pleistocen giữa -trên (qp2-3) có mức độ từ trung bình đến cao. Khu vực có khả năng bị tổn thương cao phần lớn thuộc tỉnh Cà Mau và Sóc Trăng, chiếm khoảng 54,52% diện tích khu vực nghiên cứu, khu vực có khả năng bị tổn thương mức độ trung bình thuộc các tỉnh Kiên Giang và Bạc Liêu. Kết quả này có thể được sử dụng làm cơ sở hoạch định chính sách phù hợp trong việc quy hoạch, khai thác, sử dụng tài nguyên nước dưới đất bền vững, và xây dựng các khuyến cáo hợp lý cho người dân trong khu vực nghiên cứu.Từ khóa-sự tổn thương tài nguyên nước xâm nhập mặn, chỉ số GALDIT, nước dưới đất, bán đảo Cà Mau.
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