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Chemistry in Wastewater Treatment
Published in Sreedevi Upadhyayula, Amita Chaudhary, Advanced Materials and Technologies for Wastewater Treatment, 2021
Sonali Sengupta, Chandan Kumar Pal
Fluoride can be removed to a great extent by combining activated alumina adsorption and reverse osmosis. But in some cases, coagulation using alumina coagulant is effective and economical. The removal is highly dependent on the pH of water and the coagulant dose. The optimum pH for this operation is in the range of 6–7.5. Fluoride ions reacting with aluminum hydroxide produce complex aluminum-fluoride ions, which generate flocs. Some fluoride ions adsorb on the aluminum flocs rather than producing complex ions. In a recent study, it was observed that fluoride removal efficiency was increased with increasing alum coagulant concentration and contact time. The maximum removal rate (93.3 percent) was achieved with 300 mg/l alum concentration, 45 minute contact time, and pH value of 6 when fluoride concentration in water was 3 mg/l (24). Also, removal efficiency is decreased by increasing fluoride concentration. Experimental results reveal that aluminum sulfate coagulant shows an acceptable efficiency with easy operation.
Membrane Technologies for Water Purification
Published in P.K. Tewari, Advanced Water Technologies, 2020
To understand reverse osmosis, it is necessary to know osmosis. Osmosis is a natural process. If a semipermeable membrane separates two salt solutions of different concentrations, water migrates from the dilute solution through the membrane to the concentrate solution, until the solutions have the same salt concentration. Reverse osmosis involves applying pressure on the concentrated solution side to reverse the natural flow of water, forcing the water to move from the more concentrated solution to the dilute solution. The semipermeable membrane allows water to pass through, but not the salt molecules.
Project Cost Overview
Published in Nikolay Voutchkov, Desalination Project Cost Estimating and Management, 2018
Table 1.3 presents the range of water production costs of medium and large size seawater reverse osmosis desalination projects. Information for this table is compiled based on comparative review of over 50 desalination projects in the United States, Australia, Europe, the Middle East, the Caribbean, and other parts of the world. As seen in Table 1.3, at present (in 2018 US$) the average industry-wide cost of production of desalinated water by reverse osmosis is approximately US$1.1/m3.
Catalytic wet air oxidation of phenol: Review of the reaction mechanism, kinetics, and CFD modeling
Published in Critical Reviews in Environmental Science and Technology, 2021
Tladi J. Makatsa, Jeffrey Baloyi, Thabang Ntho, Cornelius M. Masuku
There are different wastewater treatment methods available such as, biological (Krastanov et al., 2013; Pradeep et al., 2015; Alves et al., 2017; Zhou et al., 2018), adsorption (Luo et al., 2015; Frascari et al., 2019; Sun et al., 2019), electrochemical oxidation (Abbas & Abbas, 2019; Liu et al., 2019), incineration (Ye et al., 2011; Wang et al., 2019), reverse osmosis (Al-Obaidi et al., 2017; Al-Obaidi et al., 2019b, 2019a) and advanced oxidation processes (Cao et al., 2018; Dewidar et al., 2018; Radwan et al., 2018). Microbial degradation is unsuitable for waste that is too concentrated and toxic, moreover, it produces by-products that pose environmental problems such as sludge (Krastanov et al., 2013; Yu et al., 2016; Guerra-Que et al., 2019). Incineration is energy-intensive and is only applicable when waste has a chemical oxygen demand (COD) of at least 300 g/L (Cybulski, 2007). Reverse osmosis produces a concentrated and smaller waste making disposal easy, however, the costs of membrane replacement and energy requirement are high (Crini & Lichtfouse, 2019; Pervov & Nguyen, 2019; Tałałaj et al., 2019). The incapability of traditional methods to effectively remove refractory organic wastewater makes it clear that there is an urgent need to develop more efficient and economic processes of treating refractory wastewater before discharging it to water bodies.
Adsorption of fluorine ion from water by composite nonwovens
Published in The Journal of The Textile Institute, 2021
Minglei Lu, Hao Liu, Fukui Pan, Xin Ning, Jinfa Ming
Many methods have been used to remove fluoride ions from water, including reverse osmosis, electrodialysis, ion exchange, precipitation, adsorption and so on (Ahmed, 2011; Cai et al., 2018; Lahnid et al., 2008; Meenakshi & Viswanathan, 2007; Ndiaye et al., 2005; Reardon & Wang, 2000). Among them, adsorption method has become the most commonly used, because of its advantages of high efficiency and low cost (Gu et al., 2005; O’Connell et al., 2008). Low cost adsorbents have been concerned and examined for the removal of fluoride from aqueous solution (Mohammad et al., 2016). Carbon nanotubes (CNTs), owning a large specific surface area, as well as the high mechanical, chemical and thermal stabilities, are emerging as one of the most promising absorbent materials (Sarkar et al., 2018). Earlier works have reported the excellent adsorption capability of CNTs towards different contaminants such as air particles, dyes, and heavy metals (Lutiane et al., 2020). Rashid et al. reviewed different types of CNTs membranes for the removal of small air particles and the ion filtration of aqueous solution (Md. Harun-Or & Stephen, 2017). Shabaan found anionic dyes and cationic dyes were removed efficiency reaching 98.7% and 97.2% by multiwall carbon nanotubes (MWNTs), when the condition was normal pH, contact time 60 min with agitation speed 240 rpm and initial concentration of dyes 10 mg/L (Ola et al., 2020). Fiyadh et al. reviewed the most efficient adsorption process for heavy metals from water is to use functionalized CNTs with deep eutectic solvents as an adsorbent (Seef et al., 2019).
Preparation of colloidal hydrated alumina modified NaA zeolite derived from rice husk ash for effective removal of fluoride ions from water medium
Published in Journal of Asian Ceramic Societies, 2020
For removal of fluoride, the common technologies available are chemical treatment, membrane process and adsorption. However, the presence of competing ions such as phosphate, nitrate, chloride, carbonate, silicate and sulfate affects the removal efficiency. Reverse osmosis (RO) and nanofiltration (NF) method could be suitable for the removal of fluoride in the presence of the above competing ions. However, high operating cost, limited electricity supply for water pumping and washing of fouled membrane and scraping in the above processes are the major setback for rural population. Adsorption technique has proved an effective method due to its simple operation, high efficiency, little toxic sludge generation and low cost. Many adsorptive materials have been developed for the removal of F− ions, such as activated alumina [5,6], activated carbon [7], bone charcoal [8], hydrotalcite-like compounds [9,10] and mixed metal oxides [11,12]. We investigated the effects of mesoporous alumina modified with different organic acids for the removal of fluoride ions [13]. However, searching a new type of adsorbent with its interesting properties toward the removal of fluoride is of utmost important in terms of low cost and high efficiency. Zeolites have been used for the removal of radioactive cations like Cs+ and Sr2+ [14].