Fluidized-bed Crystallization Process Research Articles

Application of Fe0.66Cu0.33@Al(OH)3 catalyst from fluidized-bed crystallizer by-product for RB5 azo dye treatment using visible light-assisted photo-Fenton technology

This study aims to explore the reusability of wastewater treatment by-product for photo-Fenton process to treat an organic pollutant model. The optimal condition, reactive oxygen species (ROS), and kinetic approach in photo-Fenton process was discussed. The Metal oxide crystal pellets from are a by-product of the Fluidized-Bed Crystallization (FBC) process and can be used as a catalyst in the Photo-Fenton process. Electroplating wastewater containing iron and copper was treated via the FBC process using granulated Al(OH)3 as carrier seeds. The binary oxide of FeOOH and Cu2O on the Al(OH)3 surface (Fe0.66Cu0.33@Al(OH)3) was identified as the FBC by-product after characterization using FTIR and XPS analysis.In the photo-Fenton process, visible light from a fluorescence lamp with a wavelength of 400–610 nm was chosen as an irradiation source. Oxalic acid was added as chelating agent to form photosensitive iron oxalate species and hydrogen peroxide was applied as oxidant to generate active radical to decolorize and mineralize RB5 synthesized solution (100 mg/L). The operating conditions including the oxalic acid to pollutant ratio ([OA]0/[RB5]0) of 4.5–13.0, reaction pH (pHr) of 3–7 and initial to theoretical hydrogen peroxide molar ratio [H2O2]0/[ H2O2]theoretical of 35%–120% were optimized. Under the optimal conditions, pHr = 5.0; [H2O2]0/[RB5]0 at 75% stoichiometric and [OA]0/[RB5]0 = 9, the RB5 is almost completely decolorized after 210 min of operation and the mineralization efficiency is 58%. The contribution of •OH, O2•-, and O21 to the Photo-Fenton system was determined using ESR analysis with the addition of DMPO and TEMP as spin trap agents. The kinetic analysis reveals the observed rate constants kRB5, kOA and kR from fitting are 0.0120, 0.0054 and 0.0001 M−1s−1, respectively.

Photocatalytic oxidation of Reactive Red 195 by bimetallic Fe–Co catalyst: Statistical modeling and optimization via Box-Behnken design

Response surface methodology (RSM) is an effective tool for process optimization with multi-complex operational factors. The present work aims to model and optimize the photocatalytic oxidation (PCO) parameters of Reactive Red 195 (RR195) dye decoloration with the SiO2-supported Fe–Co catalyst (FCS) derived from a novel catalyst synthesis method, fluidized-bed crystallization (FBC) process, using Box-Behnken design (BBD) as the RSM statistical model. The Fe–Co@SiO2 catalyst was successfully fabricated using the FBC process, and it showed good catalytic activity and performance toward the degradation of RR195. The extent of the effects of pH, H2O2 dosage (HD), catalyst loading (CL), and operating time (t) on the decoloration of RR195 was studied. Hence, the order of variable significance follows the sequence: pH > t > CL > HD. pH has the most significant effect among the variables for RR195 decoloration. The decoloration efficiency predicted by the BBD model was 88.3% under the optimized operation conditions of initial pH of 3.15, 0.76 mM H2O2, 1.18 g L−1 FCS and 59.4 min of operating time. The actual decoloration efficiency was very close to the predicted value indicating that BBD can efficiently be utilized to optimize RR195 degradation with FCS under the PCO system.

Enhanced struvite (MgNH4PO4·6H2O) granulation and separation from synthetic wastewater using fluidized-bed crystallization (FBC) technology

Struvite (MgNH4PO4·6H2O) could be recovered from wastewater containing phosphorus and showed high potential as an alternative source of phosphorus fertilizer. A comparison of batch experiment and continuous crystallization processes was carried out using batch reactor and fluidized bed reactor (FBR) methods, respectively. The continuous crystallization processes for phosphorus granulation were conducted both in a seeded (FBC) and unseeded (FBHC) system. Various seed materials such as dolomite-(CaMg(CO3)2), CaHPO4, and SiO2 were applied as seed material in FBC. In the batch reactor, the operating parameters, including pH, [Mg]0/[P]0 molar ratio, and initial phosphorus concentration were first optimized. The effects of the coexisting ions (SO42−, Cl−, NO3−, Na+, K+, Ca2+) and organic pollutants (Ethylenediaminetetraacetic acid-EDTA, and Citric acid) on phosphorus-containing wastewater treatment were also examined. The hydraulic parameters of FBR (Fluidized-bed reactor), including effluent pHe, and cross-sectional surface loading (L, kg m−2 h−1) were investigated to recover phosphorus and ammonium as struvite pellets. Under optimum conditions (pHe 8.8, [Mg]0/[P]0 = 1.3/1, L = 2.4 kg-P m−2 h−1), FBC using dolomite as seed resulted in higher phosphorus removal efficiency than the FBHC system with total removal (TR) = 93.0 % and a crystallization ratio (CR) = 85.0 %. As confirmed by the XRD pattern, the solid products consist of magnesium ammonium phosphate (MgNH4PO4·6H2O) from both FBC and FBHC processes. The high crystallization ratio (CR = 85 %) and the recovery of crystal pellets (>1 mm) in the FBC process reduce the production of sludge compared to traditional chemical precipitation and FBHC processes.

Applying a Novel Sequential Double-Column Fluidized Bed Crystallization Process to the Recovery of Nitrogen, Phosphorus, and Potassium from Swine Wastewater

Given the potential shortage of critical nutrients (e.g., nitrogen, phosphorus, and potassium) predicted in the near future, nutrient recovery technologies have attracted wide attention from the sc...

Defluoridation by fluorapatite crystallization in a fluidized bed reactor under alkaline groundwater condition

Fluoride removal using fluidized bed crystallization (FBC) technology with phosphate rock (PR) and calcite as seed particles under an alkaline groundwater condition was investigated. The results indicated that the optimized operating parameters were: upflow velocity = 7.21 m h−1, Ca:P:F molar ratio = 10:4:1, and initial bed height = 120 cm. The turbidity of FBC reactor effluent was 1.5–5.9 NTU at the first phase, and then reduced to less than 1.0 NTU at the second phase, while the effluent fluoride level remained at a constant level (0.4–0.9 mg L−1) during the entire procedure. The exfoliation and dissociation of newly-generated nuclei from the seed particles surfaces after aging and drying for three days could serve as an additional filtration layer (located on the top of the expanded bed with a thickness of 1.0 cm) to intercept the fine particles in the second phase. Consequently, a rational strategy for fluidized bed operation was provided, which focused on turbidity control and fluoride removal. FBC performance can be divided into ripening and running periods according to the evolution of turbidity in effluent. Fluoride removal was achieved by the formation of amorphous calcium phosphate and then recrystallization into fluorapatite and/or FCO3-apatite and induced crystallization of fluorapatite and/or FCO3-apatite. The FBC process with additional filtration function of dissociated newly-generated nuclei could be regarded as a cleaner technology for fluoride removal; additionally, the spent seed particles could be utilized as resources in the phosphatic fertilizer industry. However, the fertilizer industry should continue to recover fluoride for further economic benefits.

Fluorine removal and calcium fluoride recovery from rare-earth smelting wastewater using fluidized bed crystallization process.

As a regulated pollutant, fluorine compounds affect the health of millions of people all over the world. Their removal using a fluidized bed reactor (FBR) through crystallization process is a new method. Instead of chemical precipitation, which produces large amounts of sludge-containing wastewater hard to recover and treat. In this work, FBR was applied to a typical rare-earth smelting wastewater containing fluorine. Influence of different seed materials, seed size, and seed amounts on the fluorine removal and calcium fluoride recovery in the FBR were studied. When silica sand was used as the seed crystal and the amounts reached 30g, the concentration of fluorine in the actual wastewater decreased to 8.2 mg L-1 or lower. The removal efficiency of fluorine and recovery ratio of calcium fluoride were obtained as 93.79% and 89.45%, respectively. The particle size of recovered calcium fluoride was about 1.5mm. The results show that FBR with silica sand as seed crystal is a feasible and economical method for removing fluorine and recovering calcium fluoride from rare-earth industrial wastewater.

Fluidized-bed crystallization of iron phosphate from solution containing phosphorus

Abstract This work demonstrates the recovery of phosphorus from a solution (150 mg-P/L) using ferrous salts (FeSO 4 ) and hydrogen peroxide (H 2 O 2 ) as precipitants through the fluidized bed crystallization (FBC) process. Jar-test experiments were conducted to investigate effective pH and molar ratios of H 2 O 2 /Fe(II) and Fe(II)/P in the removal of phosphate. The pure ferric phosphate crystal was then recovered using the FBC process and the effluent pH e and surface loading (L, kg-P/m 2 h) were tested. The results of XRD revealed that the FBC pellets were composed of the mixtures of rodolicoite and giniite, with a Fe/P molar ratio of approximately 1.1, based on elemental analysis. Under conditions pH e = 2.6, an H 2 O 2 /Fe(II) molar ratio of 0.6, an Fe(II)/P molar ration of 1.2, and L = 0.3–0.89 kg/m 2 h, a crystallization ratio of 86% and a removal efficiency of 95% were achieved.

Removal of sulfate by fluidized bed crystallization process

This study investigated the behavior of sulfate removal and gypsum crystallization in an FBR with varying seed dosage, initial sulfate concentration and calcium to sulfate concentration ratio. The effect of recycling and use of silica carriers were also evaluated. A bench-scale glass fluidized-bed reactor (FBR) with gypsum seed crystals was used. Results showed that sulfate removal and gypsum crystallization increased with the tested parameters. Sulfate conversion increased from 70.29% to 77.69% and sulfate removal from 52.34% to 65.87% when seed dosage was increased from 4.0g/L to 11.0g/L. Similar trend was observed when the initial sulfate concentration was increased from 80mM to 160mM, sulfate conversion also increased from 75.05% to 85.40% and removal from 55.29% to 77.88%. When calcium to sulfate concentration ratio was increased from 1.0 to 2.0, sulfate conversion increased from 70.40% to 79.19% and removal increased from 49.45% to 65.08%. Product crystals and silica sand carriers were found to be as effective as fresh gypsum seed crystals, hence, the potential for economic recovery of sulfate.

Removal and recovery of lead in a fluidized-bed reactor by crystallization process

Lead (Pb) is known for its high and long-term toxicity even at very low concentrations and its presence limits the reusability and recyclability of industrial wastewaters. In this study, Pb was recovered from synthetic wastewater as PbCO3 crystals via the fluidized-bed crystallization process. Pb removal exceeded 99% when the operating pH was kept within a range of 8–9 and the carbonate-to-lead molar ratio was set to 3:1. Higher Pb removals were obtained with the gradual reduction of recirculation flow rate. The present study demonstrates the potential of Pb recovery from contaminated wastewaters using fluidized-bed crystallization technology.

Study of crystal size distributions in a fluidized bed crystallizer

A fluidized bed crystallization process was investigated experimentally, characterized by a continuous withdrawal of a suspension containing target particles having narrow size distribution. Three industrially relevant substances were applied in the study, namely l-glutamic acid, l-asparagine monohydrate and ortho-aminobenzoic acid. A continuous supply of seeds, required for the establishment of a steady state, was achieved by applying ultrasonic comminution of bigger crystals and agglomerates withdrawn from the bottom of the conical shaped lower section of the fluidized bed crystallizer. The influences of the flow rate and the initial seed crystal sizes on the generated product size distribution were studied. Steady state operation was achieved, i.e. the median sizes of the collected product crystals remained constant. A simple empirical force balance model based on the Richardson–Zaki relation could be successfully applied to explain main features of the observed internal crystal size distributions.

Development and Nonlinear Analysis of Dynamic Plant Models in ProMoT /Diana

AbstractIn the process design of chemical production plants, dynamic simulation plays an important role. This paper gives a short introduction to the process modeling tool ProMoT and the simulation tool Diana. Both are open‐source programs intended for the dynamic analysis of chemical engineering and biological systems. They support the implementation and analysis of large nonlinear differential algebraic systems. An overview is given on the functionality of ProMoT and Diana. The use of the tools is illustrated by their application to an innovative fluidized bed crystallization process.

A comparative study of phosphate removal technologies using adsorption and fluidized bed crystallization process

This study compared the two novel technologies “calcium phosphate fluidized-bed crystallization (FBC) process” and “adsorption” which used an amorphous iron oxide BT-1 as the adsorbent for treating an industrial wastewater with high concentration of phosphate (1,000 mg P L–1). In the adsorption process, most of phosphorus was adsorbed rapidly initially and then reached the thermodynamics equilibrium in 24 h. The phosphate adsorptive capacity of BT-1 was 2.03 mmole/g when the PO4 3– equilibrium concentration was conditioned at 8.23 mM. The adsorption process followed the Langmuir and Temkin adsorption isotherm. In the FBC process, the optimum pH range was wider (pH > 5.3) for the total removal of phosphate than that for crystallization (optimum pH = 5.3–5.9). The total removal efficiency and crystallization ratio of phosphate were about 90% and 60%, respectively, in the optimum pH range. The EDS analysis showed that the Ca–P crystal products had an approximate 1:1:6 molar ratio of Ca:P:O. The XRD diagrams ...

Treatment of high‐level arsenic‐containing wastewater by fluidized bed crystallization process

AbstractGallium arsenide technology has been widely applied in the communication and optical electronics industries. The process of chip manufacturing produces a stream of wastewater unique in its low flow rate and high arsenic concentration. Fluidized bed crystallization (FBC) technology combines the advantages of a fluidized bed reactor and crystallization. It is highly efficient with low capital and operational costs, while producing no sludge. The waste from the FBC is small in volume, high in crystal purity and recyclable. Jar tests were first performed to evaluate the precipitation of arsenic sulfide. Then a lab‐scale fluidized bed reactor was applied to screen critical operational parameters and the process was optimized to meet the wastewater discharge standard. The results obtained in this study confirmed that the FBC process is capable of treating wastewater containing high concentrations of arsenic, reducing the concentration to µg L−1 levels. Sulfide dosage and operating pH are the two most significant parameters determining the residual arsenic concentration of the effluent, with optimum conditions of pH = 2 and S/As = 2.2 to meet the local discharge limit. Copyright © 2007 Society of Chemical Industry