China 
Africa 
Explore chapters and articles related to this topic
Ion Exchange in Purification
Published in Juan A. Asenjo, Separation Processes in Biotechnology, 2020
Elution is widely used in both analytical and preparative separations. A feed is usually diluted with an eluant and injected into a column, which is preequilib rated with the eluant. The repetitive adsorption and desorption of solutes eventually leads to separation (resolution) of the solute bands. This process is called “elution development” (Tiselius, 1943).
Chromatography
Published in Jerome Greyson, Carbon, Nitrogen, and Sulfur Pollutants and Their Determination in Air and Water, 2020
As was mentioned earlier, gas chromatography may be carried out iso-thermally or with temperature programming to reduce the retention times of analytes with high valued partition coefficients. Temperature is less effective in enhancing separations in liquid chromatography. However, liquid chromatography has its analogous operational modes. That is, since both the stationary and mobile phases contribute to separation in LC, the solvent character of the mobile phase may be used as an additional adjustable parameter to enhance separation. Thus, one may use either a mobile phase of fixed chemical composition or change its composition in some systematic way throughout the course of a run. Use of constant composition is called isocratic elution while a programmed change in composition is called gradient elution. Gradient elution requires the use of two or more solvent reservoirs (Figure 9.7), which supply the components required to vary the mobile phase composition. The parameters that may be thus adjusted include pH, ionic strength, or solvent polarity.
Comparison of aerobic and anoxic-oxic sequential batch reactors for treating textile wastewater
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
To prevent biological degradation, the collected samples from A/O-SBR and A-SBR were stored in a 1.0-liter polypropylene bottle at 4°C. The AAs were extracted from the aqueous samples using the following steps: 1) 0.45 mm glass papers were used for filtration before extraction, and 2) solid-phase extraction (SPE) columns C18 (DIONEX SOLEX, 6 mL, 1000 mg, Thermo Fisher, USA) were utilized for SPE extraction. The details of the AAs extraction process (conditioning, extraction, and elution) were previously discussed in a study by (Albahnasawi et al. 2020). The column (C18) conditioning process involved two steps. First, 5 ml of methanol was used to condition the column, followed by an additional 5 ml of ultra-pure water. This process ensures proper preparation of the column for efficient separation and analysis. After conditioning, the wastewater samples were passed through the column. The column serves as a medium to selectively retain and separate the desired analytes from the wastewater matrix. For elution, 10 ml of methanol was used to extract the AAs from the C18 column. Elution is the process of removing the retained analytes from the column, allowing them to be collected for further analysis. To concentrate the eluted analytes, nitrogen gas was used to evaporate the methanol. This step removes the solvent and leaves behind a concentrated residue of the AAs. Subsequently, a 1 ml mixture consisting of 75% ultra-pure water and 25% methanol was added to the residue. This step serves to reconstitute the analytes in a suitable solvent for subsequent analysis. The final mixture, prepared after reconstitution, was ready for injection into LC-MS/MS and GC-MS/MS instruments.
Recovery of phosphorus from wastewater: A review based on current phosphorous removal technologies
Published in Critical Reviews in Environmental Science and Technology, 2023
Yulin Zheng, Yongshan Wan, Yue Zhang, Jinsheng Huang, Yicheng Yang, Daniel C. W. Tsang, Hailong Wang, Hao Chen, Bin Gao
Metal oxyhydroxide modified porous adsorbents such as zeolites, porous silica, clay minerals have been developed for P adsorption (Bacelo et al., 2020). Acid and heat treatment are always involved in the synthesis process followed by metal impregnation to achieve ordered mesoporous or microporous structure, enhanced specific surface area, and exposed P sorption sites (Loganathan et al., 2014; Wu et al., 2020). P-laden adsorbents with magnetic properties can be recovered with a magnetic field in high gradient magnetic separators. Large scale magnetic separation relies on electrically generated magnetic wires to recover adsorbents from aqueous flow and suspension. Various magnetic adsorbents carried with magnetite, zirconium ferrate, carbonyl iron, and iron oxides (Mehta et al., 2015) have been explored for P adsorption and recovery (Bacelo et al., 2020; Yi et al., 2020). The P adsorbents are often tested to recovery P and to be regenerated for multiple application cycles. Adsorption processes have great potential on recovering P for sustainable and economic purposes. Elution can be applied as a reverse chemical desorption process by saline solutions, complexing agents, and acids or alkalis (Bacelo et al., 2020). To reverse the ligand exchange and surface complexation of P, sodium hydroxide (NaOH) is commonly accepted in the literature as the effective desorption solution for P recovery. The desorption efficiency of NaOH solutions varied by the type of P adsorbent, however, generally increases with its concentration until reaching to an optimal point. After the regeneration process, the P enriched solution can undergo P precipitation and recovery as struvite, calcium phosphate products and hydroxyapatite. Metal oxides/hydroxides and their derived adsorbents are usually with less efficient regeneration and reusability (Wu et al., 2020). For example, Ca and Mg contents in the adsorbents can generally enhance P removal in high P loadings via the formation of surface precipitation, resulting in decrease of P desorption (Kasprzyk & Gajewska, 2019; Loganathan et al., 2014). Although acid wash is able to desorb P extensively, dissolution of the metal contents may cause the damage of P surface adsorption sites followed with subsequent loss in the reusability of the adsorbent (Tan et al., 2016).