Reactive Crystallization of Calcium Sulfate Dihydrate from Acidic Wastewater and Lime

The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater dis charged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from plateletlike and nee dlelike shape to rodlike shape when the temperature was increased from 25 to 70 ℃. An increase in the agglom.

Synergistic coagulation of bauxite residue-based polyaluminum ferric chloride for dyeing wastewater treatment

Considering that Fe,Al elements in bauxite residue are active components for water purification,an effective polyaluminum ferric chloride(PAFC)coagulant derived from bauxite residue,with Fe2O3 content>5.1%,Al2O3%>6.5%,basicity>65%,was successfully prepared.The effect of as-prepared PAFC on the zeta potential for printing and dyeing wastewater was investigated.Comparing with polyferric chloride(PFC)and polyferric sulfate(PFS)for printing and dyeing wastewater treatment,prepared bauxite residue-based PAFC exhibited the optimal performance in the aspects of chromaticity and chemical oxygen demand(COD)removal rate.Furthermore,the combination of bauxite residue-based PAFC and PFS for synergy coagulation of such wastewater demonstrated an obvious positive effect.With the proportion between as-prepared PAFC and PFS to be 2.5:1,the COD of treated wastewater could be further reduced to meet the national level A standard of China,providing a promising route to solve the problem of substandard printing and dyeing sewage outfall by a simple coagulation strategy.

Leaching of lead from zinc leach residue in acidic calcium chloride aqueous solution

A process with potentially reduced environmental impacts and occupational hazards of lead-bearing zinc plant residue was studied to achieve a higher recovery of lead via a cost-effective and environmentally friendly process. This paper describes an optimization study on the leaching of lead from zinc leach residue using acidic calcium chloride aqueous solution. Six main process conditions, i.e., the solution pH value, stirring rate, concentration of CaC12 aqueous solution, liquid-to-solid （L/S） ratio, leaching temperature, and leaching time, were inves- tigated. The microstructure and components of the residue and tailing were characterized using scanning electron microscopy （SEM） and X-ray diffraction （XRD）. On the basis of experimental results, the optimum reaction conditions were determined to be a solution pH value of 1, a stirring rate of 500 r·min-1, a CaC12 aqueous solution concentration of 400 g·L-1, a liquid-to-solid mass ratio of 7：1, a leaching tempera- ture of 80℃, and a leaching time of 45 min. The leaching rate of lead under these conditions reached 93.79%, with an iron dissolution rate of 19.28%. Silica did not take part in the chemical reaction during the leaching process and was accumulated in the residue.

Efficient Separation of Butyric Acid by an Aqueous Two-phase System with Calcium Chloride

One of the bottlenecks for bioproduction of butyric acid as bulk chemical is the difficulty in separating butyric acid from the fermentation broth,compared with the petroleum-based chemical synthesis method.In the present work,a novel separation methodology was developed based on an aqueous two-phase system with inor-ganic salts.Calcium chloride was screened out for effective separation of butyric acid from butyric acid-water-salt systems.Within appropriate concentration range of butyric acid and salt,butyric acid was enriched in the upper phase and most of calcium ions remained in the lower phase.This"salting out"effect is very efficient to separate butyric acid from the simulated butyrate fermentation broth,which consists of butyric acid and acetic acid with concentration ratio of 4︰1,so that the final ratio of butyric acid/acetic acid in the upper phase is improved to 9.87. The aqueous two-phase system was used to separate butyric acid from the actual fermentation broth with satisfac-tory result.

Effect of Storage Conditions on the Sensory Quality, Colour and Texture of Fresh-Cut Minimally Processed Cabbage with the Addition of Ascorbic Acid, Citric Acid and Calcium Chloride

The aim of this study was to investigate the effect of storage conditions on the sensory quality, colour and texture of fresh-cut cabbage during the addition of ascorbic acid, citric acid and calcium chloride. Ascorbic acid maintained the overall quality for 14 days at 0℃ and 7 days at 5℃;no difference, however, was observed regarding browning of cut surface compared to the control sample at both storage temperatures. Calcium chloride maintained the overall quality and cut surface browning for 14 days at both storage temperatures. It was also found that citric acid 1% can be used for minimally processed cabbage. Soaking with citric acid helped retain the color and increased the overall acceptance and organoleptic quality of fresh cut cabbage;it reduced browning of the cut surface and protected against formation of black specks. Citric acid treatment combined with low temperature storage (0℃) prolonged the shelf life of minimally processed cabbage for 22 days, time sufficient for acceptable marketing of the product. The lightness of minimally processed cabbage decreased linearly from 70.94 ± 6 to 63.8 ± 8.5 - 61.3 ± 8 units for the chemical treatments during 22 days of storage at 0℃. Hue angle values during storage time were also significantly influenced by chemical treatments mainly at 0℃.

Vapor Pressure Measurement and Correlation of 2-Methyl-Butanol Acetate Containing Calcium Chloride

The CaCl2 solubility in 2-methyl-butanol acetate and the vapor pressure of 2-methyl-butanol acetate containing CaCl2 were measured in the range of 90-135°C and from very low salt concentration to saturation.The experimental data were correlated with two equations,a modified Antoine equation with the dissolved salt taken into account and a nonrandom two liquid-electrolyte（e-NRTL）model.Both models are in good agreement with the experimental data.This study provides essential physical data for further investigation of vapor-liquid equilibrium system containing salt.

Amelioration of Saline Soil by the Application of Gypsum, Calcium Chloride, Rice Husk and Cow Dung

A pot experiment was conducted to investigate the effect of cow dung, rice husks, calcium chloride and gypsum on soil reclamation and compare the effect of organic and inorganic amendments on soil reclamation during the period of 5th March to 20th April, 2017. The experiment was laid to fit a completely randomized design (CRD) with seven treatments [Reference soil (T0), Cow dung (T1), Rice husk (T2), Gypsum (T3), Calcium chloride (T4), Cow dung + Rice husk (T5) and Gypsum + Calcium chloride (T6)] each having three replications for this experiment. After incubation (45 days), the laboratory investigation was carried out in the Soil, Water and Environment Discipline, Khulna University, Khulna, Bangladesh. Results indicate that the individual or combined effect of gypsum (T3) was more effective in changing EC and SAR. Gypsum application in combination with calcium chloride (T6) improved the soil chemical properties by reducing the EC. Among the treatment, calcium chloride (T4) had a remarkable effect in reducing sodium adsorption ratio and gypsum had a remarkable effect in reducing pH. Cow dung (T1), rice husk (T2), combination of cow dung and rice husk (T5) were less effective to reduce EC, pH and SAR. It’s measured for soils of different soil amendments varied significantly

Effect of Calcium Chloride Addition on Properties of Corundum Spinel Castable

Corundum spinel castable was prepared using tabular corundum as aggregates,white fused corundum powder,spinel powder and alumina powder as the matrix,pure calcium aluminate cement as a binder,and extra adding calcium chloride(0,1%,2%,and 3%,by mass).The effects of the CaCl2 addition on the cold physical properties,the hot strength,the thermal shock resistance and the microstructure of the castable were studied.The results show that,for the corundum spinel castable fired at 1550℃,with the increase of the CaCl2 addition from 0 to 3%,the cold strengthes first increase,then decrease,the apparent porosity increases,the volume density decreases,and the linear change rate first decreases and then increases,while the overall change is not significant;however,the hot modulus of rupture and the thermal shock resistance are obviously improved.This is mainly due to that,CaCl2 is evenly distributed in the castable in the form of solution,and reacts with Al2O3 to form small flake CA6 crystals,which evenly distributed in the sample matrix strengthening and toughening the material.

Kinetics of the Chlorination of Copper （I） Sulphide by Calcium Chloride in the Presence of Oxygen

The chemism of the chlorination of copper （I） sulphide by calcium chloride in the presence of oxygen has been determined based on the thermodynamic analysis in the Cu2S-CaCl2-O2 system as well as characterization of used raw materials and obtained products. The influence of temperature （from 473 to 773 K）, time （from 2 to 120 min）, oxygen flow （from 20 to 100 L/h） and calcium chloride quantity （from 5 to 40%） on the chlorination degree has been investigated. Kinetic analysis and the activation energy values of 20.89 kJ/mol showed that the chlorination of copper （I） sulphide by calcium chloride in the presence of oxygen is diffusion controlled.

Improving Photosynthetic Responses during Recovery from Heat Treatments with Brassinosteroid and Calcium Chloride in Indian Bread Wheat Cultivars

Climate change is expected to unleash severe and frequent heat waves in future, adversely affecting crop productivity. The aim of this study was to examine the effect of two separate episodes of heat stress, mimicking heat wave conditions on the physiology of four Indian bread wheat cultivars and to study the ameliorating effects of epibrassinolide (BR) and calcium chloride on the recovery of these cultivars. The two thermo-tolerant cultivars C306 and K7903 suffered less inhibition of photosystem II efficiency as compared to the two thermo-susceptible cultivars HD2329 and PBW343. Application of BR and calcium chloride resulted in faster recovery in all the four cultivars. Measurement of the minimum fluorescence (Fo) versus temperature curves revealed a higher inflection temperature of Fo (Ti) for the two tolerant cultivars as compared to the susceptible cultivars, emphasizing greater thermo stability of the photosynthetic apparatus. The two thermo-tolerant cultivars showed higher photochemistry (ΦPSII) relative to the two susceptible cultivars. An increase in the steady state fluorescence was observed in both the susceptible cultivars as compared to the tolerant cultivars. Expression analysis revealed faster recovery of the transcripts involved in photosynthesis in tolerant cultivars as compared to susceptible cultivars. Exogenous application of the ameliorating compounds resulted in faster recovery of transcripts in all the cultivars. The result suggested that under severe stress conditions tolerant cultivars showed faster recovery and a better thermo-stability of its photosynthetic apparatus as compared to susceptible cultivars and application of epibrassinolide and calcium chloride could ameliorate the damaging effect of severe temperature stress to a considerable level in all the four cultivars under study.

The Effect of Calcium Chloride on the Microbiological Characteristics of Fermented Chile Pepper （Capsicum annuum cv. Mesilla Cayenne） Mash

Fermented chile pepper mash （Capsicum annuum cv. Mesilla Cayenne） is a major industrial food product in New Mexico. The fermentation of chile pepper mash depends on temperature, acidity, salt concentration, dissolved air, available carbohydrates and enzymes. The objective of this study was to evaluate the effects of the addition of calcium chloride （CaCI2） on the microbial characteristics of the pepper mash fermentation. Nine five gallon buckets were prepared with pepper that had been washed and ground by the manufacturer, each with 15% sodium chloride added. The buckets were allotted randomly to 1 of 3 treatments. The treatments included no CaCl2, 0.2% CaCl2 and 0.4% CaCl2 added to the pepper mash. Samples were stored at room temperature and sampled over a 3 months period to examine changes in the microflora. Chile mash samples were serially diluted in butterfield＇s phosphate buffer for microbial enumeration. Aerobic plate counts were conducted by pour plating with an overlay. Petrifilms were used for E. coil/coliform counts and Enterobacteriaceae. Yeasts and molds were surface plated on Rose Bengal Chloramphenicol agar while streptococci and lactobacilli were plated onto M17 and acidified MRS respectively. Aerobic plate counts, coliforms, E. coli, Enterobacteriaceae, yeast, mold, lactobacilli, and streptococci were not affected by CaCl2 level. The addition of 0.4% CaCl2 was found to have no effect on the chile pepper mash fermentation.

Biodegradation of oil wastewater by free and immobilized Yarrowia lipolytica W29

The ability of Yarrowia lipolytica W29 immobilized by calcium alginate to degrade oil and chemical oxygen demand （COD） was examined. The degradation rules of oil and COD by immobilized cells with the cell density of 6.65 × 10^6 CFU/mL degraded 2000 mg/L oil and 2000 mg/L COD within 50 h at 30℃ （pH 7.0, 150 r/min）, similarly to those of free cells, and the degradation efficiencies of oil and COD by immobilized cells were above 80%, respectively. The factors affecting oil and COD degradation by immobilized cells were investigated, the results showed that immobilized cells had high thermostability compared to that of free cells, and substrate concentration significantly affected degrading ability of immobilized cells. Storage stability and reusability tests revealed that the oil degradation ability of immobilized cells was stable after storing at 4~C for 30 d and reuse for 12 times, respectively, the COD degradation rate of immobilized cells was also maintained 82% at the sixth cycle. These results suggested that immobilized Y lipolytica might be applicable to a wastewater treatment system for the removal of oil and COD.

Development of an evaporation crystallizer for desalination of alkaline organic wastewater before incineration

A wastewater evaporation-desalination pretreatment method was introduced to remove the Na+ and K+ salts in volatile organic compounds (VOCs) wastewater before it was fed into the incinerator. VOCs in the wastewater were volatilized in the evaporation system and then the vapor was combusted in an incinerator. Simulated phenol wastewater containing sodium chloride was evaporated and concentrated and sodium chloride was crystallized in different parameters. The experimental results showed that the higher initial concentration of sodium chloride increases the ratio of volatilization of VOCs, which was due to the effect of “salting out” (a decrease in the solubility of the nonelectrolyte in the solution, or more rigorously, an increase in its activity coef-ficient, caused by the salt addition (Furter and Cook, 1967)). When evaporation speed was increased from 1.67 ml/min to 2.73 ml/min, the total removal coefficient of sodium chloride was about 99.88%～99.99%. This pretreatment procedure eliminates the slag phenomenon caused by Na+ and K+ salts during wastewater incineration, so the incinerator could operate continuously, and the wastewater evaporation could increase the heat value of wastewater, and the operation cost would be reduced.

Experimental investigation and theoretical modeling on scale behaviors of high salinity wastewater in zero liquid discharge process of coal chemical industry

Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stability of the device.In this study,the effects of solution temperature,steel,reaction time and wall roughness on fouling were investigated.The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively,and the formation of scale was observed by SEM.The results show that with temperature increasing,Q235 steel is the most difficult to scale.Scaling rate of all salt scales reaches a maximum after 12 h,and the fouling rate decreases significantly from 12 to 48 h.It gradually stabilizes at 48 to 96 h.With the roughness increasing,the thickness of fouling layer increases,and a linear relationship is presented for 1 to 10 h.By comparing actual and simulated wastewater scaling rates,the relationship between actual and simulated wastewater scaling rates is y=ax-0.494.The composition of the scale was analyzed,calcium carbonate is the main product and increases with fouling time.Based on the above-mentioned results combining literatures,the hybrid prediction model with calcium carbonate as the main product is put forward.It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.

Two-stage treatment process of pickling wastewater in the cold-rolling production of stainless steel

Based on the characteristics of pickling wastewater in the cold-rolling production of stainless steel, a new processing route, featuring source sludge reduction, wastewater two-stage treatment, heavy metal-contained sludge and calcium salt sludge separating recovery, was proposed. As shown by the research results, after the two-stage process treatment, the effluent water can steadily reach the emission standards, the sludge yield can be decreased by more than 8% ; within the heavy metal-contained sludge, the recovery rates of Fc,Cr and Ni can either reach or surpass 95% ,and the total content ofF and S can drop to around 3%. Therefore,the sludge in the front part can be used as ferric dust. In the calcium salt sludge ,the recovery rate of F can either reach or surpass 85% ,and the total contents of Fe,Cr and Ni can fall below 0.5%. So the sludge in the rear part can be used as fluorgypsum or fluorite. Meanwhile,the results of the analysis on heavy metals leaching toxicity and morphologic distribution indicate that the two kinds of sectionalized sludge are not classified as hazardous wastes, which have a stable behavior and better utilization values compared with the former mixed- sludge.

Treatment of sauce wastewater by sequencing biological -chemical reactor (SBCR)

The concept of SBCR was put forward to treat sauce wastewater. Further study showed that adding appropriate amount of calcium chloride to SBR can improve the quality of effluent. The removal rate of COD and color was 84% and 80%, 36%, 96% higher than those of traditional SBR respectively. The results of continuous experiments and biophase observing showed that calcium chloride accumulation increased the sludge production slightly while the sludge dewatering characteristic was improved.

Pretreatment of Wastewater Streams from Petroleum/Petrochemical Industries Using Coagulation

Coagulation-flocculation processes using different types of conventional coagulants, namely, ferric chloride (FeCl3), aluminum sulfate (AL2(SO4)3·18H2O), lime and ferrous sulfate (FeSO4) were investigated using the Jar-test technique. A further aim is to determine the optimum conditions for the treatment of industrial wastewater effluents i.e. coagulant dosage, mixing rate, temperature and pH control. Under optimal condition of process parameters, coagulation/flocculation process was able to lower the turbidity well below the permissible level (1.8 NTU). The results indicate that ferric chloride had superior efficiency compared with other coagulants with efficient dose of 800 mg/l. The optimal initial pH of the effluents that enhanced the turbidity removal was 8.6. The temperature showed no significant effect on the turbidity removal.

A Novel Coating Method for Create Filter Media Capable to Remove Phosphate from Wastewater Effectively

Filtration materials coating with metallic oxides represented a good method for phosphate sorption. However, most of the researchers utilize chemicals as a source of metallic oxides and heating process to set the chemicals over the filtration materials. This study is aimed to introduce the furnace bottom ash FBA as a source of metallic oxides;it is available free because it is dumped as a waste material from power generation plants. The method of creating new filter media involves coating the limestone and sand by FBA, and the ordinary Portland cement OPC utilized as binder to binding the mixture materials. The water is the factor which is responsible for activating the OPC. All factors such as mixed materials ratio, water content and age of reaction have subjected to optimization process. The results revealed that the optimal mixture for phosphate removal consists of 40% FBA, 5% OPC from dry weight of supporting material, 35% water ratio from the total weight of FBA and OPC, and 14 days are enough to complete the materials reaction. Limestone-furnace bottom ash LFBA indicated high capacity for phosphate sorption and possibility of efficiency regenerate. This study demonstrates a new method for coating the filtration materials more convenient with sustainability approach.

Purification of Produced Water from a Sour Oilfield in South Kuwait. 2. Oil-Water Separation and Crystallization of Calcium Carbonate

Oil-water separation for produced water (PW) originating from an oil extraction site in South Kuwait was carried out using bleached, esterified cellulosic material from used coffee grounds. Thereafter, earth-alkaline metal ions, specifically calcium ions, of the de-oiled PW were removed by precipitation with sodium carbonate to give access to pure sodium chloride as industrial salt from the remaining PW. While the purity of the precipitated calcium carbonate (CaCO3) depends on the precipitation conditions, CaCO3 of up to 95.48% purity can be obtained, which makes it a salable product. The precipitation of CaCO3 decreases the amount of calcium ions in PW from 11,300 ppm to 84 ppm.