•A process integrating block freeze concentration and precipitation is proposed.•Initial concentration and thawing rate influence the block freeze concentration.•Phosphorus and fluoride were ...separated in the first and second thawed fractions.•Thawing led to the recovery of pure water in the last thawed fraction.•Calcium fluoride, fluorapatite, and hydroxyapatite were produced by precipitation.
The work aims at developing a process for treating industrial wastewater from phosphoric acid and fertilizer production units by a coupled block freeze concentration-precipitation process. First, the block freeze concentration study, carried out on synthetic phosphoric acid solutions of concentrations ranging between 1.31 wt% 29.93 wt%, has shown that the purity of the ice block is strongly dependent on the initial concentration, the freeze duration, the thawing rate and the ice block temperature. Second, the block freeze concentration study, performed on a solution containing an orthophosphate-fluoride mixture, showed that the process increased the purity of the ice by the migration of occluded fluoride and orthophosphate ions until reaching a removal efficiency of F− and PO43− upper than 94 %. Further treatment by precipitation was studied on the first thawed fraction resulting from the freezing step. The results of the recovered liquid confirmed that, in the pH range between 2.4 and 12.73, the removal of fluoride and orthophosphate increased from 9.8 % to 96 % and from 6.3 % to 99 %, respectively. Precipitates characterization using methods such as X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy combined with energy dispersive X-ray analysis, indicated that CaF2, Ca5(PO4)3(OH)F and Ca5(PO4)3(OH) were successfully produced.
Desalination reverse osmosis reject brine-based porous geopolymer (RO/GP) was produced and investigated as an improved adsorbent for phosphorus (P) removal from tainted seawater, brackish water, ...river water, and municipal wastewater effluent. The RO reject brine/geopolymer was produced by reacting metakaolin and fly ash with a Na-alkali activator and anhydrous RO brine as a sacrificial template. The influence of RO reject brine content on water absorption, porosity, mechanical, and structural properties were examined. The developed RO-based geopolymers exhibited the greatest porosity (58.3–84.2 % vol%), a significant ratio of open porosity to total porosity (67.7–92.1 %), and outstanding compression strength (3.6–10.4 MPa). The produced RO/GP structure has an adsorption capacity of 92.4 mg-P/g. The sequestration reaction of phosphorus by RO/GP is of pseudo-second-order kinetic behavior via Chi-squared (χ2), RMSE, and determination coefficient (R2) values. Regarding their agreement with Langmuir behavior, the phosphorus adsorption uptakes occur in homogeneous and monolayer states. The reaction is exothermic, spontaneous, and favorable. The RO/GP exhibits significant affinity for phosphorus co-existing with Cl−, Na+, SO42−, K+, HCO3−, and Ca2+. The RO/GP shows high safety during the adsorption investigation, with a total cost of 0.32 $/kg-P.
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•RO reject brine as a precursor of porous alkali-activated materials.•Highly porous building geopolymers were obtained with porosity from 58.3 to 84.2 % vol%.•RO/GP was applied to remove phosphate ions from contaminated real aqueous media.•The maximum phosphate uptake capacity of RO/GP was 92.4 mg/g.•RO/GP has prospective safety and feasibility as a promising material for phosphate ions removal from contaminated media.
In this work, the salinization mechanisms were highlighted in the coastal area between Sidi Abed and Ouled Ghanem (El Jadida Province, Morocco). This study was based on analyzing and discussing the ...physicochemical data of water samples from 73 wells distributed in the whole studied region. Firstly, the results of the principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed that the study area is composed of three main groups. This classification is firstly based on the proximity of the wells to the seawater. In fact, it was found that the first and second groups of wells which are located in the coastal fringe are characterized by high concentration of sodium and chloride and EC values whereas lower values are found in the third group that is located in upstream. Moreover, the results also showed the influence of the hydrogeological characteristics of the area where the wells are located on the composition of the water samples. The evaluation of the hydrochemical facies using Piper trilinear diagram have also confirmed these results and showed the probable contribution of seawater intrusion in the modification of wells composition by ion exchange process and by increasing the concentration of sodium and chloride. Then, the groundwater quality were assessed using Sodium Adsorption Ratio (SAR) and sodium percentage (Na %) parameters. In order to define the salinization processes occurring in the aquifer, the binary diagrams between chloride and the other elements were plotted. It was found that the groundwater is contaminated by seawater intrusion which is accompanied by ions exchange depending on the hydrogeological characteristics of the area.
•The salinity of groundwater in the region Sidi Abed−Oulad Ghanem was evaluated.•The origin of groundwater salinization in this coastal aquifer was studied.•Several tools and methods were applied to draw relevant conclusions.•The salinization is mainly due to marine intrusion and aquifer rock dissolution.•Some cares should be taken in order to properly exploit this natural water resource.
Reject desalination brine is a rich source of salts and valuable materials. But, its disposal into the external environment generates a major source of pollution. This paper investigated the ...production of reactive CaO from reverse osmosis (RO) reject brine and its use as adsorbent for phosphate removal from contaminated seawater and RO industrial waste. This study was realized via two steps. Firstly, the recovery of Ca-phase from reject brine via oxalic acid at optimized conditions resulting clcium oxalate monohydrate, and its calcination at 900°C for 2 h to produce the reactive CaO. Secondly, the produced reactive CaO was doped by Fe3O4 via co-precipitation method to produce reactive CaO@Fe3O4 composites. The reactive CaO@Fe3O4 was explored as a potential adsorbent with enhanced capacity for phosphate ions (PO43−) removal. The estimated maximum reactive CaO@Fe3O4 uptake capacity for PO43− (106.3 mg/g) is comparatively higher than the identified values for the reactive CaO (72.8 mg/g) and Fe3O4 (41.6 mg/g). The kinetics of the PO43− uptake reaction via reactive CaO@Fe3O4 obey the Pseudo-Second order model (R2 > 0.98) and the equilibrium time was determined after 450 min. The equilibrium study of the demonstrated reaction exhibited excellent agreement with the isotherm assumption of the Freundlich model implying multilayer and heterogeneous adsorption processes. The thermodynamic aspect of PO43− adsorption reaction is favorable and exothermic. The adsorbent selectivity, reusability experiments and realistic study were also discussed . Furthermore, the computational study using DMs was applied to better understand the interaction for {PO43−/CaO(111)&CaO@Fe3O4(111)} systems. The simulation results demonstrate favorable, more stable, spontaneous adsorption and exothermic for PO43−/CaO@Fe3O4(111) than PO43−/CaO(111)complex. Overall, CaO@Fe3O4(111) could serve as a effective and reusable adsorbent for phosphate ions recovery from aqueous solutions.
In this work, we will study the nitrate pollution level in the groundwater of the coastal area between Sidi Abed and Ouled Ghanem (Province of El Jadida, Morocco). This area is characterized by the ...dominance of vegetable market gardening and cattle breeding. The aim of this study is to identify the main factors contributing in nitrate pollution. It was based on piezo-metric data, Lambert coordinate and the results of physicochemical analyzes of the water from 73 wells. The principal components analysis (PCA) was applied to all data collected. Firstly, the descriptive statistics shows that the well depth varies between 1 and 75 m with 16.5 m as average. Nitrate levels vary between 25.7 mg/l and 161.5 mg/l with 89 mg/l as average. Secondly, the results of the PCA revealed the impact of the depth, correlated with the geographic location, on the quality of 89% of the wells. However, 11% of the wells remain indifferent to this parameter. In this case, we can say that nitrate pollution is mainly due to the geological nature of the region allowing greater infiltration of nitrates.
In this work, we will study the nitrate pollution level in the groundwater of the coastal area between Sidi Abed and Ouled Ghanem (Province of El Jadida, Morocco). This area is characterized by the ...dominance of vegetable market gardening and cattle breeding. The aim of this study is to identify the main factors contributing in nitrate pollution. It was based on piezo-metric data, Lambert coordinate and the results of physicochemical analyzes of the water from 73 wells. The principal components analysis (PCA) was applied to all data collected. Firstly, the descriptive statistics shows that the well depth varies between 1 and 75 m with 16.5 m as average. Nitrate levels vary between 25.7 mg/l and 161.5 mg/l with 89 mg/l as average. Secondly, the results of the PCA revealed the impact of the depth, correlated with the geographic location, on the quality of 89% of the wells. However, 11% of the wells remain indifferent to this parameter. In this case, we can say that nitrate pollution is mainly due to the geological nature of the region allowing greater infiltration of nitrates.
