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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. [Display omitted] • Seed-induced crystal growth of C–BaPB enabled rapid boron removal. • Spiral surface growth was the rate-limiting step near pH pzc. • Continuous crystal growth of granular C–BaPB seeds removed 90% boron in FBC. • Two FBCs in-series eliminated boron from 500 to 8 mg-B/L, >92% on granular seeds. [ABSTRACT FROM AUTHOR]

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 SiO 2 -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@SiO 2 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, H 2 O 2 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 H 2 O 2 , 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. [Display omitted] • FBC-derived Fe–Co catalyst exhibited good catalytic activity toward RR195 degradation. • pH has the most significant effect among the variables for RR195 decoloration. • BBD can be efficiently utilized to optimize the degradation of RR195 with FCS under the PCO process. [ABSTRACT FROM AUTHOR]

The electrocoagulation (EC) using metallic Ni foam as electrodes was studied for the removal of boron from solution. The electrolytic parameters were pH (4–12), current density (0.6–2.5 mA cm −2 ), and initial concentration of boron (10–100 mg L −1 ). Experimental results revealed that removal efficiency was maximized at pH 8–9, and decreased as the pH increased beyond that range. At particular onset potentials (0.5–0.8 V vs. Hg/HgO), the micro-granular nickel oxide that was created on the surface of the nickel metal substrate depended on pH, as determined by cyclic voltammetry. Most of the crystallites of the precipitates comprised a mixed phase of β-Ni(OH) 2 , a theophrastite phase, and NiOOH, as revealed by XRD and SEM analyses. A current density of 1.25 mA cm −2 was effective in the EC of boron, and increasing the concentration of boric acid from 10 to 100 mg L −1 did not greatly impair removal efficiency. A kinetic investigation revealed that the reaction followed a pseudo-second order rate model. The optimal conditions under which 99.2% of boron was removed from treated wastewater with 10 mg L −1 -B, leaving less than 0.1 mg L −1 -B in the electrolyte, were pH 8 and 1.25 mA cm −2 for 120 min. [ABSTRACT FROM AUTHOR]

Animal and human studies have suggested that phthalate alters thyroid hormone concentrations. This study investigated the associations between phthalate exposure during the first trimester and thyroid hormones in pregnant women and their newborns. Pregnant women were enrolled from the prospective Ma’anshan Birth Cohort study in China. A standard questionnaire was completed by the women at the first antenatal visit. Seven phthalate metabolites were measured in one-spot urine at enrolment (10.0 ± 2.1 gestational weeks), as were thyroid hormone levels in maternal and cord sera. Multivariable linear regression showed that 1-standard deviation (SD) increase in natural log (ln)-transformed mono(2-ethylhexyl) phthalate (MEHP) and mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) was associated with 0.163 μg/dL ( p = 0.001) and 0.173 μg/dL ( p = 0.001) decreases in maternal total thyroxine (TT 4 ). Both MEHP and MEHHP were negatively associated with maternal free thyroxine (FT 4 ; β: −0.013, p < 0.001 and β: −0.011, p = 0.001, respectively) and positively associated with maternal thyroid-stimulating hormone (β: 0.101, p < 0.001; β: 0.132, p < 0.001, respectively). An inverse association was observed between monobenzyl phthalate and maternal TT 4 and FT 4 . A 1-SD increase in ln-transformed monoethyl phthalate was inversely associated with maternal TT 4 (β: −0.151, p = 0.002). By contrast, the concentrations of phthalate metabolites in urine were not associated with those of thyroid hormone in cord serum. Our analysis suggested that phthalate exposure during the first trimester disrupts maternal thyroid hormone levels. [ABSTRACT FROM AUTHOR]

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 :[M] 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. [Display omitted] • High-purity Fe–Cu particles were recovered from wastewater. • A total metal removal of 99% was achieved for both synthetic and real wastewater. • Cost reduction of up to 88% compared to conventional chemical precipitation. [ABSTRACT FROM AUTHOR]

Atmospheric carbon dioxide (CO 2) imbalance due to anthropogenic emissions has direct impact in climate change. Recent advancements in the mitigation of industrial CO 2 emissions have been brought about by a paradigm shift from mere CO 2 capture onto various adsorbents to CO 2 conversion into high value products. The present study proposes a system which involves the conversion of CO 2 into high purity, low moisture, compact and large CaCO 3 solids through homogeneous granulation in a fluidized-bed reactor (FBR). In the present study, synthetic solutions of potassium carbonate (K 2 CO 3) and calcium hydroxide (Ca(OH) 2) were used as sources of carbonate and precipitant, respectively. The effects of the degree of supersaturation (S) as chemical loading and influx flow rate (Q T) as hydraulic loading on CaCO 3 granulation efficiency were investigated. In the study, S was varied from 10.2 to 10.8 and Q T from 40 to 80 mL min−1 while the operating pH and calcium-is-to-carbonate molar ratio ([Ca2+/[CO 3 2−) were set at 10 ± 0.2 and 1.50, respectively. Results showed that carbonate ions end product distribution had a highest carbonate granulation efficiency at [Carbonate] G of 95–96% using S of 10.6 and Q T of 60 mL min−1. Characterization of the granules confirmed high purity calcium carbonate. Overall, the transformation of industrial CO 2 emissions into a valuable solid product can be a significant move towards the mitigation of climate change from anthropogenic emissions. Image 101088 • Carbon dioxide was recovered by calcium carbonate granulation. • Calcium carbonate removal and granulation efficiencies exceeded 95%. • Effects of supersaturation and cross-sectional loading on granulation were examined. • Physic-chemical characteristics of the recovered granules were analyzed. [ABSTRACT FROM AUTHOR]

Abstract: This work demonstrates the combination of UV/persulfate and adsorption processes for treating 2,2,3,3-tetrafluoro-1-propanol (TFP) wastewater. Under the optimum conditions, 20mM persulfate , 254nm UV–C, and pH 3, 99.7% of TOC removal from an initial TFP solution of 1.39mM was achieved. The photolysis of persulfate by UV irradiation yielded the sulfate radical with high activity, which mineralized most of the TFP in 2h. The released fluoride ions were then removed by using a waste iron oxide, BT-4 adsorbent. 20gL−1 BT-4 adsorbed 95% of the fluoride that was produced by mineralization of 1.39mM TFP. The kinetics and isotherms of adsorption were examined to determine the fluoride removal efficiency of BT-4 which co-existed with the sulfate ions from the consumed sulfate radicals. Accordingly, the kinetics of adsorption was described by a pseudo-second-order rate model, while the adsorption isotherms were well fitted with the Langmuir model. BT-4 had a high adsorption capacity of 26.4mgg−1 (25°C) in removing the fluoride from TFP mineralization, suggesting that the co-existing sulfate ions never significantly affected the fluoride removal efficiency. [Copyright &y& Elsevier]

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 Cu 2 O on the Al(OH) 3 surface (Fe 0.66 Cu 0.33 @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 [H 2 O 2 ] 0 /[ H 2 O 2 ] theoretical of 35%–120% were optimized. Under the optimal conditions, pH r = 5.0; [H 2 O 2 ] 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, O 2 •-, and O 2 1 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 k RB5 , k OA and k R from fitting are 0.0120, 0.0054 and 0.0001 M−1s−1, respectively. [Display omitted] • The binary oxide of by-product from FBC process is useful for organics treatment. • Treatability of azo dye RB5 by visible light-assisted photo-Fenton was investigated. • RB5 was completely degraded and mineralized of 55% using a 75% stoichiometric dosage of H 2 O 2 with the addition of oxalic acid at pH 5. • Up to 55% of TOC was mineralized mainly by O 2 •- and O 2 1. • Rate modeling of RB5 and TOC removal were explained using consecutive kinetics. [ABSTRACT FROM AUTHOR]

The environment is affected by agricultural, domestic, and industrial activities that lead to drastic problems such as global warming and wastewater generation. Wastewater pollution is of public concern, making the treatment of persistent pollutants in water and wastewater highly imperative. Several conventional treatment technologies (physicochemical processes, biological degradation, and oxidative processes) have been applied to water and wastewater remediation, but each has numerous limitations. To address this issue, treatment using bimetallic systems has been extensively studied. This study reviews existing research on various synthesis methods for the preparation of bimetallic catalysts and their catalytic application to the treatment of organic (dyes, phenol and its derivatives, and chlorinated organic compounds) and inorganic pollutants (nitrate and hexavalent chromium) from water and wastewater. The reaction mechanisms, removal efficiencies, operating conditions, and research progress are also presented. The results reveal that Fe-based bimetallic catalysts are one of the most efficient heterogeneous catalysts for the treatment of organic and inorganic contamination. Furthermore, the roles and performances of bimetallic catalysts in the removal of these environmental contaminants are different. Image 1 • Bimetallic catalysts possess different physicochemical properties than those of monometallic catalysts. • Bimetallic catalysts have remarkable catalytic properties and functions, and exhibit high reducibility. • Organic and inorganic pollutants in water and wastewater can be treated using bimetallic systems. [ABSTRACT FROM AUTHOR]

Activated carbon (AC), prepared from dried loofah sponge, was supported on nickel foam to fabricate AC/Ni electrodes. The characteristics of ammonium electrosorption on AC/Ni electrodes was studied. Results showed that AC prepared in one-step activation (without pre-pyrolysis), i.e., OAC, had relatively low crystallinity, high mesoporosity, and high specific capacitance compared to those made in two-step carbonation followed by activation. Adsorption and desorption density of NH 4 + were measured at constant potential of −1.0 V (vs. Hg/HgO) and +0.1 V (vs. Hg/HgO), respectively. Non-faradaic charging contributed to the electrochemical storage and adsorption of ammonium ions on the AC surface with a maximal charge efficiency of 80%, at an applied potential of −1.0 V (vs. Hg/HgO). Multiple-layer adsorption isotherm better described the electrosorption of ammonium ion on OAC/Ni electrodes yielding a maximum adsorption capacity of 6 mg-N g−1, which was comparable with other similar systems. Overall, results clearly demonstrated the effect of synthesis strategy on the capacitive charging behaviors of AC/Ni electrodes and its relationship to NH 4 + electrosorption. Image 1 • Dried loofah sponge was used to prepare activated carbon successfully. • One step activation without pre-pyrolysis yielded activated carbon of high specific capacity. • Activated carbon-nickel foam (OAC/Ni) electrode exhibited 80% charge efficiency. • OAC/Ni electrodes yielded a maximum ammonium adsorption capacity of 6 mg-N g−1. [ABSTRACT FROM AUTHOR]

Abstract This work reports the use of ferrioxalate complexes to assist solar photo-Fenton treatment of pentachlorophenol (PCP) in aqueous medium at mild pH, which inhibits the precipitation of iron hydroxides and allows working at a low iron dosage. The experimental parameters were optimized by assessing the effect of initial concentrations of H 2 O 2 (0–2.5 mM) and Fe(II) (2–10 mg/L), pH (3.0–9.0) and iron/oxalic acid molar ratios (1:0–1:13.5) on total organic carbon (TOC) removal. Ferrioxalate-assisted solar photo-Fenton achieved 97.5% mineralization in 120 min, clearly outperforming conventional Fenton and solar photo-Fenton. The presence of photosensitive ferrioxalate complexes accounted for the enhancement, as a result of Fe(II) regeneration that accelerated the hydroxyl radical (OH) production. The time course of H 2 O 2 and Fe(II) concentrations was evaluated under different iron/oxalic acid ratios. The five carboxylic acids determined by ion-exclusion HPLC and the eight aromatic by-products identified by GC-MS allowed the proposal of a degradation pathway that included hydroxylation, dechlorination and dimerization steps. Complete chloride ion release was achieved after 90 min of treatment. Highlights • Up to 97.5% mineralization achieved by ferrioxalate-assisted solar photo-Fenton process. • Similar TOC abatement was obtained within pH range 3.0–6.0 • Complete dechlorination of PCP at 90 min using low iron dosage (5 mg/L) at pH 5.0 • Fe(III) was maintained soluble, being efficiently reduced to Fe(II) in the presence of oxalate. • Up to 8 aromatic products found by GC-MS: hydroxylation, dechlorination and dimerization. [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]

Heavy metal removal is a significant task that protects our water resources. Fluidized-bed homogeneous granulation process (FBHGP) was used to treat nickel containing wastewaters by recovering nickel in the form of nickel carbonate hydroxide granules with low moisture content rather than soft sludge. This study investigated nickel removal and recovery through HFBGP by determining the effects of varying influent nickel concentrations, [CO 3 2− : Ni 2+ ] molar ratios, and pH of the precipitant. This was conducted in a continuous process using a laboratory scale fluidized-bed reactor that determined the effects driven by supersaturation. The best operating conditions that resulted in a 98.8% nickel removal and 97.8% granulation efficiency were 200 mg L −1 influent nickel concentration, 2.0 M R of [CO 3 −2 :Ni +2 ], and 10.7 pH of precipitant. Based on SEM analysis, the granules formed have sizes between 0.50 mm and 0.15 mm. EDS results showed that the atomic percentages of nickel carbon, and hydrogen were ∼50%, ∼9–12%, and ∼35% respectively, representing the nickel carbonate compound. The XRD results showed the low symmetry of the granules formed that confirmed the characteristics of nullaginite mineral of Ni 2 (CO 3 )(OH) 2 . [ABSTRACT FROM AUTHOR]

The strong oxidant, persulfate (PS, S 2 O 8 2−), was applied to treat the synthetic wastewater of benzoic acid (BA) under UV irradiation. UVC light initiated a chain reaction that derived the sulfate radical (SO 4 •-) and hydroxyl radical (HO•) from S 2 O 8 2− ion. The experiment parameters, including light irradiation (UVA and UVC), pH, dose ratio ([PS] 0 /[BA] 0), initial concentration ([BA] 0 , mg/L), was optimized based on degradation efficiency and total organic carbon (TOC) removal of BA, which reached up to 100% and 96%, respectively, under pH 3.0. The best dose ratio was close to equivalent stoichiometry (and [PS] 0 /[BA] 0 = 15) for the treatment of 100 mg-BA/L, suggesting that UV/S 2 O 8 2− was able to completely convert BA to carbon dioxide and water. The scavenging test showed that SO 4 •- contributed to about 60% of degradation rate, which the HO• predominated the mineralization rate, i.e., TOC removal. A consecutive kinetic model was proposed to clarify the reaction sequence and rate-determining factor of photo-persulfate oxidation for benzoic acid. [Display omitted] • The UVC-persulfate oxidation of benzoic acid was investigated. • Up to 100% of Benzoic acid was degraded within 1 h. • Up to 96% of TOC was mineralized within 1 h. • Sulfate radical is the predominant agent in benzoic acid mineralization. [ABSTRACT FROM AUTHOR]

Chemical oxo-precipitation (COP), which combines treatment with an oxidant and precipitation using metal salts, was developed for treating boron-containing water under milder conditions (room temperature, pH 10) than those of conventional coagulation processes. The concentration of boron compounds was 1000 mg-B L-1. They included boric acid (H3BO3) and perborate (NaBO3). Precipitation using calcium chloride eliminated 80% of the boron from the perborate solution, but was unable to treat boric acid. COP uses hydrogen peroxide (H2O2) to pretreat boric acid, substantially increasing the removal of boron from boric acid solution by chemical precipitation from less than 5% to 80%. Furthermore, of alkaline earth metals, barium ions are the most efficient precipitant, and can increase the 80% boron removal to 98.5% at [H2O2]/[B] and [Ba]/[B] molar ratios of 2 and 1, respectively. The residual boron in the end water of COP contained 15 ppm-B: this value cannot be achieved using conventional coagulation processes. [ABSTRACT FROM AUTHOR]