Purification of protease from pre-treated tuna spleen extract by ultrafiltration: An altered operational mode involving critical flux condition and diafiltration

A comparison of struvite precipitation thermodynamics and kinetics modelling techniques

Solution thermodynamics and kinetic modelling applied to struvite crystallisation-precipitation were reviewed from diverse references to determine proximity between predicted and cited experimental measurements. These simulations show the expected variability range of struvite saturation calculation when only limited solution compositional information is given, showing acceptable agreement between predicted and experimental struvite mass. This work also compares results from struvite crystallisation kinetic studies on liquid phase species depletion, crystallisation induction time, primary nucleation, secondary nucleation, crystal growth, and crystal aggregation. Large inconsistencies between reported kinetics were observed in many scenarios. Variations in species depletion models highlighted that they are only suitably applied to the specific system from which they were regressed. Spontaneous primary nucleation was predicted to occur in the range of SI = 0.237-0.8. Predicted primary nucleation rates vary over at least 10 orders of magnitude (depending on supersaturation) because of uncertainties in interfacial tension and maximum achievable nucleation rate. Secondary nucleation rates are more agreeable, varying over approximately two orders of magnitude. Growth rates varied over five orders of magnitude due to variations in experimental conditions. Aggregation rates are not thoroughly examined enough to make any inferences.

Struvite production from anaerobic digestate of piggery wastewater using ferronickel slag as a magnesium source

This study aimed to fully recover ammonia contained at a high concentration in anaerobic digestate of piggery wastewater (ADPW) by forming struvite. As magnesium and phosphorus sources, ferronickel slag (FNS) and K₂HPO₄ were used, respectively. By leaching 200 g L^-1 of FNS with 3.0 M H₂SO₄, 10,309 mg L^-1 of magnesium ions were extracted, and this acid-leachate of FNS (FNSL) also contained 5965 mg L^-1 of total iron. In order to simultaneously remove both high concentrations of organic matters in ADPW and iron in FNSL which were known to hinder struvite formation, the mixture of ADPW and FNSL was added with H₂O₂ at the H₂O₂/Fe molar ratio of 0.75 and pH 4.0. After Fenton reaction, removal efficiencies of COD and total iron reached 77.36% and 99.89%, respectively. Then COD and an iron-reduced mixture of ADPW and FNSL were added with K₂HPO₄ satisfying Mg:N:P molar ratio of 1.2:1:1.15 at pH 9.5 to produce struvite for 1 h. From 1 L of ADPW (2.21 g NH₃-N), 0.65 L of FNSL (4.65 g Mg²⁺), and 5.63 g of PO₄ ^3-P, 46.7 g of precipitates were obtained. Overall removal efficiencies of magnesium, NH₃-N, and phosphorus were 98.59%, 94.25%, and 99.97%, respectively. Obtained precipitates were analysed by using XRD, XRF, SEM-EDX and found to be struvite with impurities of potassium and metals. Additionally, the economic feasibility of FNS was assessed by estimating chemical costs of various magnesium sources.

Optimization of phosphate recovery as struvite from synthetic distillery wastewater using a chemical equilibrium model

This study investigates the feasibility of recovery of phosphorus via struvite precipitation from a synthetic anaerobically treated distillery spent wash by optimizing the process using a chemical equilibrium model, namely Visual MINTEQ. Process parameters such as Mg²⁺, [Formula: see text], and [Formula: see text] ion concentrations and pH were used as inputs into the model. Increasing the molar ratio of [Formula: see text] from 0.8:1 to 1.6:1 at pH 9 led to an increase in phosphate recovery from 88.2 to 99.5%. The model and experimental results were in good agreement in terms of phosphate recovery, indicating that the Visual MINTEQ model can be used to pre-determine the process parameters for struvite synthesis. Increasing the concentration of calcium ion adversely affected the synthesis and purity of struvite, whereas the presence of melanoidins had no significant impact. This study demonstrates that phosphorus recovery through struvite precipitation is a sustainable approach to reclaim phosphorus from high-strength industrial wastewater.

One-Step Ultrafiltration Process for Separation and Purification of a Keratinolytic Protease Produced with Feather Meal

A purification technique to obtain keratinolytic proteases produced byBacillussp. P45 in a medium containing chicken feather meal as substrate is presented. The experiments were carried out in a dead-end ultrafiltration unit, and the influence of the membrane cutoff, pH of enzymatic extract, and operating pressure on the purification of keratinase were studied. The one-step ultrafiltration process with the membrane molecular mass cutoff of 10 kDa at pH 8.0 and operating pressure of 0.147 MPa showed an enzyme recovery of 87.8% and a 4.1-fold purification factor. It is showed that ultrafiltration could be potentially used in the purification of keratinases.