Topic
Lime softening
About: Lime softening is a research topic. Over the lifetime, 184 publications have been published within this topic receiving 2223 citations. The topic is also known as: Clark's process.
Papers published on a yearly basis
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Papers
TL;DR: In this article, the results and attributes of two new separation processes using ion exchange fibers (IX-fibers) were discussed, and the first process involves the selective removal of arsenic using hybridized IX-fiber that contain dispersed hydrated ferric oxide (HFO) nanoparticles.
Abstract: Separation processes using ion exchange materials are ubiquitous regarding the selective removal of contaminants of environmental concern. Recently, highly regulated contaminants, such as arsenic, have gained notoriety on account of carcinogenic effects and subsequent promulgation of new drinking water standards by the United States Environmental Protection Agency. Other nonregulated compounds such as hardness (e.g., Ca2+, Mg2+), pose a particular concern to avoid scaling in heat-transfer equipment, foulingz in membranes, and high consumption of detergents and sequestering chemicals in cooling and wash water. In general, ion exchange processes used to remove hardness generate concentrated brine or mineral acid as a waste regenerant stream. Residuals management and long-term sustainability issues will continue to be major concerns with these processes. The subject paper reports and discusses the results and attributes of two new separation processes using ion exchange fibers (IX-fibers). The first process involves the selective removal of arsenic using hybridized IX-fibers that contain dispersed hydrated ferric oxide (HFO) nanoparticles. Anion-exchanger-supported HFO particles offered a high arsenic removal capacity; less than 10% of influent arsenic broke through after 30,000 bed volumes. Hybrid fibers were also amenable to efficient regeneration with 2% NaOH and 2% NaCl and capable of simultaneous removal of both arsenic(V) and arsenic(III). The second process involves the environmentally benign removal of hardness. Most importantly, this process uses harvested snowmelt (or rainwater) sparged with carbon dioxide as the regenerant. Consequently, the spent regenerant does not contain a high concentration of aggressive chemicals such as sodium chloride or acid like traditional ion-exchange processes nor does the process produce voluminous sludges as does lime softening. The bulk of carbon dioxide consumed during regeneration remains sequestered in the aqueous phase as alkalinity. For both treatment strategies, IX-fibers form the heart of the process. They are essentially thin cylindrical polymeric strands 10–20 μm in diameter with functional groups residing near to the fiber surface. Low intraparticle diffusional resistance is the underlying reason why calcium loaded weak acid IX-fibers are amenable to efficient regeneration using either snowmelt or rainwater sparged with carbon dioxide. Additionally, for hybrid IX-fibers, enhanced adsorption kinetics may offer the possibility for certain point of use applications, which are unavailable to their resin counterparts. © 2006 American Institute of Chemical Engineers Environ Prog, 2006
114 citations
TL;DR: In this article, the major treatment methods applied for uranium removal from groundwater, with specific applications in drinking water treatment, are reviewed, including pump-and-treat, anion exchange, and the use of adsorbents, such as iron oxides, or titanium dioxide, as well as the application of coagulation processes with the addition of Fe/Al salts, or by lime softening.
Abstract: In the present article, the major treatment methods applied for uranium removal from groundwater, with specific applications in drinking water treatment, are reviewed. These include pump-and-treat technologies, such as membrane filtration methods, anion exchange, and the use of adsorbents, such as iron oxides, or titanium dioxide, as well as the application of coagulation processes with the addition of Fe/Al salts, or by lime softening. In all cases, uranium removal is mainly dependent on its speciation, which is greatly affected by the (usually coexisting) carbonate ions in the contaminated water. Under circumneutral pH values, uranium forms anionic complexes with carbonate of the type , or . In situ treatment technologies comprise mainly the use of permeable reactive barriers. These contain reactive materials, such as zero valent iron or hydroxyapatite, and uranium is usually removed by reduction to the respective insoluble products of U(IV); reducing bacteria, when present, can play a suppleme...
111 citations
TL;DR: The most common method of color removal is lime-soda softening as discussed by the authors, which removes a substantial amount of the color in waters with high concentrations of magnesium, particularly in waters of low alkalinity and low buffer capacity.
Abstract: platinum-cobalt scale. Most municipalities, however, endeavor to maintain lower concentrations, on the order of 10 or even less. Many industrial users, of which the pulp and paper industry is possibly the best example, require waters with low concentrations of color. For the production of highbrightness bleached pulp and paper, the maximum concentration of color tolerated is usually 5 or less. In many areas of the United States where the prevailing aquifers are limestones and where solution-type topoggraphy permits high recharge of surface water, considerable concentrations of organic color may be present in water from both deep and shallow wells. In such instances, lime-soda softening has been shown to remove a substantial amount of the color, particularly in waters with high concentrations of magnesium. The concentration of organic color in water from more than twenty wells supplying the Hialeah plant at Miami, Fla., is reduced to 5-8 by lime softening followed by free residual chlorination. Organic color, however, is more characteristic of soft surface waters of low alkalinity and, consequently, of low buffer capacity. The most common method of color
76 citations
TL;DR: The results of this work show that intermediate treatment of NF/RO concentrate is capable of producing treated concentrate with water quality approximately equal to the initial source water.
74 citations
Patent•
3 Oct 2008
TL;DR: In this article, a method and system for treating an aqueous liquid containing dissolved minerals and dissolved hydrocarbons is described, which utilizes a warm lime softening system in fluid communication with the waste water feed stream, wherein sludge from the warm limesoftening system is recycled to improve lime utilization and enhance silica and boron removal without the addition of an external source of magnesium.
Abstract: The invention relates to a method and system for treating an aqueous liquid containing dissolved minerals and dissolved hydrocarbons. Method steps and apparatus for treating a waste water feed stream are disclosed which utilize a warm lime softening system in fluid communication with the waste water feed stream, wherein sludge from the warm lime softening system is recycled to improve lime utilization and enhance silica and boron removal without the addition of an external source of magnesium. In addition, a microfiltration system and/or an air stripper system may be used in fluid communication with at least one reverse osmosis system to produce a treatment water that meets state and federal guidelines for surface discharge.
74 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 3 |
| 2020 | 5 |
| 2019 | 6 |
| 2018 | 3 |
| 2017 | 6 |
| 2016 | 14 |