Cation-exchange membrane fouling and cleaning in bipolar membrane electrodialysis of industrial glutamate production wastewater

Bipolar membrane electrodialysis (BMED) was used to regenerate ammonium and sulfuric acid from industrial glutamate production wastewater. However, membrane fouling was observed during BMED process. The aim of present study was to identify the nature of fouling deposits for cation-exchange membranes (CEMs) and investigates the effect of various cleaning methods on the removal efficiency of fouling. A significant amount of fouling deposits were observed by scanning electron microscopy (SEM) on the CEM surface in contact with the base stream after processing five successive batches of BMED. Furthermore, the deterioration in physical and chemical membrane parameters indicated the presence of the inner membrane fouling. Elemental analysis mapping results showed that the fouling on CEM surface was identified as calcium hydroxide along with the mixtures of calcium carbonate and magnesium hydroxide. The effect of hydraulic cleaning, acid cleaning and a combination thereof with ultrasound on deposits removal was investigated. The combination of acid cleaning and ultrasound treatment has been proposed to be the most effective cleaning method, which removed the CEM fouling on the surface and in the interior membrane as well as restored the membrane performance efficiently. After 60 s of ultrasound treatment in 1% HCl solution, the cleaned membrane presented a plane and clean surface similar to an original one in the analysis of SEM. The results of surface elemental analysis and membrane parameters detection indicated that the chemical composition and the performance of cleaned membrane were very close to an original one. (C) 2011 Elsevier B.V. All rights reserved

Transport properties of amino acid ions at isoelectric point in electrodialysis

The protonation and deprotonation reactions in systems containing amino acids play an important role and lead to some principal peculiarities of their transport in solution and membrane. A better understanding of the behavior of bipolar amino acid ions in electrodialysis would help a lot to facilitate or restrain the transfer of amino acids depending on the applications. In this work, the dissociation and migration of glutamic acid (acidic) and lysine (basic) in electrodialysis was ascertained using the special seven-compartment assemblies. It showed that acidic glutamic acid was inclined to be negatively charged and migrate towards the anode, while basic lysine preferred to be positively charged and migrate towards the cathode. Besides, the process performances of the same amino acids were also investigated during the conventional electrodialysis with the five-compartment assemblies. The pH and adsorption characteristics of membranes indicated that the above conclusion was valid for the conventional electrodialysis as well. Moreover, process parameters, i.e. overall current efficiency and energy consumption, were also assessed and compared for the electrodialysis of glutamic acid and lysine solutions. (C) 2016 Elsevier B.V. All rights reserved

Influence of different resins on the amino acid recovery by resin-filling electrodialysis

Compared to the concentration and separation of inorganic salts, recovery of amino acids by electrodialysis (ED) is normally more difficult due to their weak dissociation ability, relatively complex structure and zwitterionic properties. In this work, three kinds of resins, inert resin, 001 x 4 resin (strongly acidic) and 201 x 4 resin (strongly basic), were added in the diluted compartments of membrane stack to facilitate the transport of amino acids. The effect of the property and quantity of resin-filling on the ED behavior of glutamate (acidic) and lysine (basic) was investigated respectively. It was found that the promotion effect of different resins on the transport of amino acids was in this order: 201 x 4 > 001 x 4 >= inert resin. For inert resin, when the percentage of resin filling in the compartments reached 25% or 50%, the improvement in transport of amino acids was most significant. This was attributed to the influence of resins on the hydraulic conditions in the diluted compartments. As for 201 x 4 and 001 x 4 ion exchange resins, the higher quantity of resin-filling produced more obvious positive effect on the migration of amino acids as compared to inert resin, which was caused by the superior conductive and catalytic ability of the functional groups. (C) 2015 Elsevier B.V. All rights reserved

Characterization of cation-exchange membrane fouling during bipolar membrane electrodialysis of monosodium glutamate isoelectric supernatant

BACKGROUND: A novel procedure that involved regeneration and recycling of ammonia and sulfuric acid from monosodium glutamate isoelectric supernatant with bipolar membrane electrodialysis (BMED) was proposed. As the performance of the membranes deteriorated during the batch runs, fouling of the cation-exchange membrane (CEM) in contact with the base cell was studied

Total Hip Arthroplasty in Patients with Crowe III/IV Developmental Dysplasia of the Hip: Acetabular Morphology and Reconstruction Techniques

The severe anatomic deformities render acetabular reconstruction as one of the greatest challenges in total hip arthroplasty (THA) for patients with Crowe III/IV developmental dysplasia of the hip (DDH). Thorough understanding of acetabular morphology and bone defect is the basis of acetabular reconstruction techniques. Researchers have proposed either true acetabulum position reconstruction or high hip center (HHC) position reconstruction. The former can obtain the optimal hip biomechanics, including bulk femoral head autograft, acetabular medial wall displacement osteotomy, and acetabular component medialization, while the latter is relatively easy for hip reduction, as it can avoid neurovascular lesions and obtain more bone coverage; however, it cannot achieve good hip biomechanics. Both techniques have their own advantages and disadvantages. Although there is no consensus on which approach is better, most researchers suggest the true acetabulum position reconstruction. Based on the various acetabular deformities in DDH patients, evaluation of acetabular morphology, bone defect, and bone stock using the 3D image and acetabular component simulation techniques, as well as the soft tissue tension around the hip joint, individualized acetabular reconstruction plans can be formulated and appropriate techniques can be selected to acquire desired clinical outcomes