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The mixture of copper and iron often results in materials with favorable properties. The material production processes involving these metals including electroplating produce hazardous wastewater. In this study, the Fluidized Bed Homogeneous Crystallization (FBHC) process was applied to treat iron and copper-containing wastewater. The initial iron copper particles were successfully recovered from synthetic wastewater with [Fe] 0 :[Cu] 0 of 2:1, the total metal concentration of 3 mM, at effluent pH = 7.75 ± 0.75, with the upflow velocity (U) of 1.76 m/h. The agglomerates hardening process is a crucial step for initial particle synthesis. The SEM analysis reveals the spherical particle's densified crust and porous core. The particle formation mechanism which includes the formation of the nucleus, attachment of precipitate flakes, and densification of particles was proposed after microscopic observation. The initial particles synthesized were used to initiate the treatment of synthetic wastewater at the operating condition pH = 7.75 ± 0.5, [Fe] 0 :[Cu] 0 of 2:1, the total metal concentration of 3 mM, [CO 3 2- ] 0  = 1.2:1, and U of 28.66 m/h which results in the total metal removal of 99% and crystallization ratio of 90% and 88% for iron and copper respectively. The conditions were then applied to treat electroplating wastewater and resulted in the total metal removal of 99% for both iron and copper and a crystallization ratio of 83% and 79% for iron and copper, respectively. The treatment provided advantages in terms of treating larger amounts of sludge while eliminating the need to provide seed thus yielding a higher purity of product.0  = 1.2:1, and U of 28.66 m/h which results in the total metal removal of 99% and crystallization ratio of 90% and 88% for iron and copper respectively. The conditions were then applied to treat electroplating wastewater and resulted in the total metal removal of 99% for both iron and copper and a crystallization ratio of 83% and 79% for iron and copper, respectively. The treatment provided advantages in terms of treating larger amounts of sludge while eliminating the need to provide seed thus yielding a higher purity of product., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Chemical oxo-precipitation (COP) is an enhanced precipitation method for boron removal with the conversion of boric acid to perborate anions. When using barium-based precipitant, the boron can be effectively precipitated as barium perborates (BaPBs). The phase transformation of BaPBs from amorphous (A-BaPB, Ba(B(OH) 3 OOH) 2 ) to crystalline (C-BaPB, BaB 2 (OO) 2 (OH) 4 ) form is crucial for effective boron removal. However, scaling up this phase transformation of BaPBs is hindered by poor diffusion. This study aims to promote the growth of C-BaPB through seed-induced crystal growth, eliminating the need for phase transformation. By examining the relationship between crystal growth rate and supersaturation, surface spiral growth was identified as the rate-limiting step of the growth of micron-sized seeds near pH pzc . To enable continuous crystal growth, granular seeds of C-BaPB were prepared and employed as the medium for fluidized-bed crystallization (FBC). The system reached steady state 3 hydraulic retention times, achieving 90% boron removal. The effect of surface loading, ionic strength, and dosages on steady-state crystal growth rate was studied, revealing a shift of the rate-limiting step in FBC to diffusion. Lastly, the system that constituted of two FBCs in-series for sequential crystallization of A-BaPB and C-BaPB was demonstrated. The integrated system provided 97.8% of boron removal from synthetic wastewater containing 500 mg-B/L, with 92.3% of boron crystallized on the granular seeds of BaPBs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This work demonstrated the removal of lead (Pb) from aqueous solution using fluidized-bed crystallization (FBC, using silica sand as seeds) and fluidized-bed homogeneous crystallization (FBHC, without seeds) systems. Synthetic lead wastewater with concentrations of 10, 40 and 200 ppm were treated. The results thus obtained indicated that effluent pH was an essential parameter in determining the efficiency of FBC and FBHC. A comparison between theoretical solubility and residual Pb in effluents revealed that FBHC in the predictable metastable region of pH 6.5–8.5 guaranteed 99% Pb removal and a crystallization ratio of 95% (CR%). XRD analysis suggested that the lead carbonate of FBHC products comprised either a cerussite (PbCO 3 ) or a hydrocerussite (Pb 3 (CO 3 ) 2 (OH) 2 ) phase, depending on pH. FBHC was proven to be effective in remediating lead wastewater under optimal hydraulic conditions (initial molar ratio of [Na 2 CO 3 ]/[Pb] > 1.2, upflow velocity = 25–35 m h −1 and pH e = 7.2 ± 0.4), which were all similar to those in FBC. The cross-section loading (L, kg m −2 L −1 ) depended on the input Pb level; L was controlled at 0.15 kg m −2 h −1 for treating 10 ppm-Pb and was increased to 5.73 kg m −2 h −1 for 40 and 200 ppm-Pb, optimizing the FBHC and FBC processes. Without the addition of seed materials, FBHC recovered purer lead carbonate than did FBC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sulfide-containing synthetic wastewater was treated by fluidized-bed homogeneous crystallization. • Fluidized bed homogeneous crystallization technology does not need to add the heterogeneous seeds. • The crystallization efficiency of sulfide recovered as zinc sulfide particles reached 97.8%. • Supersaturation is calculated to determine the optimum condition of sulfur crystallization. Sulfide wastewater that is anthropogenically generated from industrial activities is highly corrosive, hazardous, and harms the natural ecosystem. This study uses a novel fluidized-bed homogeneous crystallization (FBHC) method to remove sulfide ions from an aqueous solution. Zinc is used as a precipitant to crystallize ZnS homogeneously in the FBHC reactor to reduce the sludge, which is commonly produced in a conventional chemical precipitation process. The optimal pH value, [Zn2+] 0 /[S2-] 0 M ratio, sulfide cross-sectional surface loading (L, kg-S/m2.hr), and hydraulic retention time (HRT) for the system are established, to optimize the sulfur removal efficiency. The maximum crystallization ratio and the total removal efficiency for sulfur are 97.7% and 98.8%, respectively, at pH = 5.4, a [Zn2+] 0 /[S2-] 0 M ratio of 1, a cross-sectional surface loading of 2.2 kg-S/m2.hr, and an HRT number of 6 with an initial sulfur concentration of 320 mg/L. The solid products are collected and identified as zinc sulfide (wurtzite) using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). [ABSTRACT FROM AUTHOR]

• Extremely high concentrations form denser sludge instead of suspended particulates. • A preliminary experiment formed atypical flake-like CaF 2 particles. • Various flow regimes can be crucial to CaF 2 granulation. • A 2.0-mm glass-bead bed enhances the over-all granulation efficiency. • CaF 2 homogenous granulation is achieved with 98% removal and granulation. Excessive and industrial advances have increased fluoride quantity in the effluents. However, the environmental carrying capacity for fluoride is relatively slim immediately affecting both aquatic and terrestrial animals while its transport can further contaminate the water source. To protect the public and the environment, different environmental agencies globally set their respective effluent standard restricting F- concentration to 15 mg/L as the median value. However, various processes from previous investigations have mostly been limited in treating 100–1000 mg F-/L with secondary pollution commonly overlooked. Re-assessing the available defluoridation technologies, chemical precipitation has still been the most feasible among the technologies, especially extremely high fluoride concentrations. In this study, fluoride removal through chemical precipitation was investigated using conventional precipitation and fluidized-bed homogeneous crystallization. Parameters such as a wide range of initial concentrations from 100 to10,000 mg/L and pH 2.0–11.0 under conventional precipitation were varied and analyzed. To reduce high water content sludge, a 550-mL cylindrical glass was modified to simulate a fluidized-bed reactor to investigate homogenous crystallization varying influent concentration, bed-support size, and fluid flow. Results showed that chemical precipitation could effectively remove fluoride even at very high fluoride concentrations ranging from 1,000 to 10,000 mg/L. Alternatively in the fluidized-bed granulation process, an initial very low flow without recirculation flow was required to initiate particle formation. The predominant size of the recovered particle was < 0.2 mm which was relatively heavy atypically not reaching the upper region of the reactor. Under the observed optimum condition with an initial fluoride concentration of 450 mg/L, both total removal and crystallization ratio could reach ∼ 98% efficiency lowering fluoride concentration to < 15.0 mg F-/L within 7 days. [ABSTRACT FROM AUTHOR]

Sulfide-containing wastewater, characterized by its foul odor, corrosiveness, and toxicity, can endanger human health. Fluidized-bed homogeneous crystallization (FBHC) avoids the excessive sludge production commonly associated with conventional chemical precipitation methods. In this study, FBHC is used to treat sulfur-containing synthetic wastewater. Furthermore, nickel-containing wastewater was utilized as a precipitant in the system, hence the advantage of simultaneous sulfur and nickel removal from the wastewater. The operating parameters, including pH, a precipitant dosage of [Ni2+] 0 /[S2−] 0 , and cross-sectional surface loading (L S , kg/m2h) are optimized. The optimum operating conditions of pH 9.8 ± 0.3, [Ni2+] 0 /[S2−] 0 = 0.8, and L S = 1.5 kg/m2h results in total sulfur removal (TR) of 95.7% and crystallization ratio (CR) of 94.8%. The effect of organic compounds (acetic acid, oxalic acid, EDTA, and citric acid) and inorganic ions (NO 3 −, CO 3 2−, PO 4 3−, F−, and Cl−) on the nickel sulfide granulation process was discussed. [Display omitted] • Sulfide wastewater could be treated by FBHC. • The total sulfur removal achieves 95.7%. • The waste cost is 86.0% lower than chemical precipitation. [ABSTRACT FROM AUTHOR]

The crystallization of struvite in fluidized-bed crystallizer (FBC) was performed to treat synthetic wastewaters that contain phosphorous. Under optimal conditions (pH 9.5, molar ratio Mg/N/P = 1.3/4/1, struvite seed dose (53–297 μm) = 30 g L −1 , total flow rate = 12 ml min −1 , reflux = 120 ml min −1 ), the removal of phosphate (PR) and the crystallization ratio (CR) were 95.8% and 93.5%, respectively. Based on a thermodynamic prediction, the supersaturation, which was obtained from the difference between the theoretical solubility and phosphate concentration, predominated the crystallization efficiency and the properties of the struvite pellets, such as their morphology, particle size and apparent density. Coexisting ions NO 3 − (80, 160 ppm), CH 2 COOH − (260, 520 ppm), F − (650, 1300 ppm) and SO 4 2− (650, 1300 ppm), were utilized to prepare P-containing wastewaters. Of these ions, SO 4 2− (1300 ppm) remarkably reduced the capability of FBC to remove phosphate from solution. In the presence of NO 3 − and CH 3 COO − (for synthesizing TFT-LCD wastewater), and F − and SO 4 2− (for synthesizing semiconductor wastewater), CR% was lower than in pure water, although the ultimate PR% did not differ significantly. [ABSTRACT FROM AUTHOR]

• Simultaneous recovery of phosphorus and potassium from urine was achieved. • Recovery of P and K reached 98.4% and 70.5%, respectively at low Mg:K ratio of 1.25. • K-struvite pellets recovered have low water content and high purity (>95%). • The fluidized bed homogeneous crystallization (FBHC) was performed without seeds. • FBHC recovery can help yield a profit of $0.26/m3-urine. Most of nutrients in municipal wastewater originate from human urine. In this study, a novel fluidized-bed homogeneous crystallization process was developed for the simultaneous recovery of phosphorus (P) and potassium (K) from synthetic human urine. The operational variables including pH, Mg:K ratios and up-flow velocity were tested in the laboratory. The total removal of P and K (TR%) reached 98.4% and 70.5%, respectively, and the crystallization ratios (CR%) were 86.5% and 62.3%, respectively, at conditions of pH 10 ± 0.2, molar ratio Mg:K = 1.25, initial concentrations 850 mg P/L and 1830 mg K/L. The SEM and XRD analyses showed that the fluidized bed homogeneous crystallization (FBHC) product was pure magnesium potassium phosphate (K-struvite) (average size = 0.85 mm; purity = 95 ± 3%). The modelling of minimum fluidization velocity (MFV) resulted in values of up-flow 1.5–2.0 times the MFV for the effective fluidization. The profit of the recovery of P and K from human urine via FBHC process could be $0.26/m3-urine. [ABSTRACT FROM AUTHOR]