Juan An

Kinetic and Thermodynamic Studies on the Phosphate Adsorption Removal by Dolomite Mineral

The efficiency of dolomite to remove phosphate from aqueous solutions was investigated. The experimental results showed that the removal of phosphate by dolomite was rapid (the removal rate over 95% in 60 min) when the initial phosphate concentration is at the range of 10–50 mg/L. Several kinetic models including intraparticle diffusion model, pseudo-first-order model, Elovich model, and pseudo-second-order model were employed to evaluate the kinetics data of phosphate adsorption onto dolomite and pseudo-second-order model was recommended to describe the adsorption kinetics characteristics. Further analysis of the adsorption kinetics indicated that the phosphate removal process was mainly controlled by chemical bonding or chemisorption. Moreover, both Freundlich and Langmuir adsorption isotherms were used to evaluate the experimental data. The results indicated that Langmuir isotherm was more suitable to describe the adsorption characteristics of dolomite. Maximum adsorption capacity of phosphate by dolomite was found to be 4.76 mg phosphorous/g dolomite. Thermodynamic studies showed that phosphate adsorption was exothermic. The study implies that dolomite is an excellent low cost material for phosphate removal in wastewater treatment process.

Phosphate adsorption characteristics of wasted low-grade iron ore with phosphorus used as natural adsorbent for aqueous solution

AbstractA low-grade iron ore with phosphorus (LGIOWP), the extensive industrial solid waste generated in mining of high phosphorus iron ore, was investigated to assess the effectiveness for the removal of phosphate from aqueous solution. The factors influencing the adsorption were examined, and the related adsorption mechanism was discussed. The results showed that pH value had a significant effect on the phosphate removal. The optimum pH value for phosphate adsorption was 5.6. The adsorption of phosphate mainly on hematite ligand exchange is likely the key mechanism for phosphate removal when pH is in the range of 1−9. When pH value was above 9, the presence of dolomite played an important role in phosphate removal. The adsorption capacity is enhanced with a higher initial phosphate concentration. Kinetic studies show that the adsorption follow pseudo-second-order kinetic model. Langmuir and Freundlich isotherms were used to simulate the adsorption equilibrium data. The adsorption fits well with the Lang...

Acid–base properties and surface complexation modeling of phosphate anion adsorption by wasted low grade iron ore with high phosphorus

The adsorption phenomena and specific reaction processes of phosphate onto wasted low grade iron ore with high phosphorus (WLGIOWHP) were studied in this work. Zeta potential and Fourier transform infrared spectroscopy (FTIR) analyses were used to elucidate the interaction mechanism between WLGIOWHP and aqueous solution. The results implied that the main adsorption mechanism was the replacement of surface hydroxyl groups by phosphate via the formation of inner-sphere complex. The adsorption process was characterized by chemical adsorption onto WLGIOWHP. The non-electrostatic model (NEM) was used to simulate the surface adsorption of phosphate onto WLGIOWHP. The total surface site density and protonation constants for NEM (N(T)=1.6×10(-4) mol/g, K(a1)=2.2×10(-4), K(a2)=6.82×10(-9)) were obtained by non-linear data fitting of acid-base titrations. In addition, the NEM was used to establish the surface adsorption complexation modeling of phosphate onto WLGIOWHP. The model successfully predicted the adsorption of phosphate onto WLGIOWHP from municipal wastewater.

Removal of Phosphate Anions from Aqueous Solutions Using Dolomite as Adsorbent

Dolomite, an industrial solid material was used as an adsorbent to remove phosphate anions from wastewater. The effects of initial pH, initial phosphate concentration, reaction time, reaction temperature and adsorbent dosage on the phosphate removal efficiency were investigated. The results show that the phosphate removal efficiency exceed 99% under the conditions of pH 9.5, temperature 30 °C, reaction time 50 min, particle size <0.074 mm, initial phosphate concentration 50 mg•L-1, adsorbent dosage 10g•L-1 and stirring speed 250 r/min. After phosphate removal reaction, the residual phosphate concentrations completely meet the requirement of national discharge standards of the second category pollution (GB 1A (TP = 0.5 mgL-1)).

Roasting Pretreatment of High-Sulfur Bauxite with Low-Median Grade in Chongqing China

High-sulfur bauxite is being paid more and more attention due to the decreasing grade for traditional ore in China. There is rich high-sulfur bauxite with low-median grade in Chongqing, which is being treated with Bayer process with dressing. But there still exist excess impurities of sulfur and iron in the alumina product. The effect of surface density, particle size, temperature and time on the roasting desulfurization process was studied. The optimized roasting conditions are as follows: 750 °C, 60 minutes, the surface density of 7.6 kg / m2 and the particle size from 147 μm to 177 μm for the ore. Under these conditions, residual sulfur in the roasted ore is lower than 0.4%, which can meet the requirements of alumina production. Meanwhile, the digestion performance of the roasted ore improves. Roasting desulfurization might be one of methods for treating high-sulfur bauxite with low-median grade, and better technical and economic results might be attained when it is used to treat high-sulfur bauxite with organic and / or goethite impurites.

Removal of Phosphorus from High-Phosphorus Iron Ores by Sodium Roasting

The phosphorus removal from high-phosphorus iron ores by sodium roasting was studied. The effects of ratio of NaOH to NaCO3, roasting temperature and reaction time on the dephosphorization ratio were investigated. The results showed that the dephosphorization ratio can reach 80.1% under the conditions of ratio of NaOH to NaCO3 5:6, roasting temperature 1100°C, and reaction time 120min. After sodium roasting, the content of phosphorus in iron ore sample complied completely with the requirements of steel production.

Removal of Water-Soluble Manganese Ions from Electrolytic Manganese Residues by Hydrometallurgical Process

Electrolytic manganese residues containing a substantial amount of manganese are a potential pollution. Removing water-soluble manganese ions from electrolytic manganese residues by hydrometallurgical process was discussed. In the work, the basic property of the electrolytic manganese residues was analyzed. Based on it, we proposed the suitable method to remove Mn2+ from the slag by pollution-free oxidation in alkaline solution. The results shown that the best conditions to remove Mn2+ were pH 10.5, temperature 55 °C, the flow rate of hydrogen peroxide 0.50 mL·L-1·min-1 and agitation speed 250 r/min. At the optimum condition, the removal ratio of water-soluble Mn2+ exceeded 99.9% and the concentration of Mn2+ in the final solutions was about 3 mg/L.

Removal Phosphorous from High Phosphorous Converter Steel Making Slag by Hydrometallurgical Process

Removing phosphorus from high phosphorus converter steel slag by hydrometallurgical method was studied in this paper. The influence of different dephosphorizting agents on the effect of phosphorus slag was investigated, and high efficient dephosphorizating agent was found. The effects of reaction time, liquid to solid ratio, stirring speed, reaction temperature and dephosphorizing agent concentration on the impact of dephosphorization were studied. The results showed that on the conditions of the reaction time 40 min, slag particle size <0.147 mm, liquid to solid ratio of 4:1, stirring speed 400 rpm, the reaction temperature 25 °C, and dephosphorizing agent concentration 5 mol/L, the optimum dephosphorization results were achieved. The dephosphorization ratio can reach 70%, and the phosphorus content in steel slag decreased from 1.03% to 0.46%, the total iron content increase from 30.676% to above 44%.

Removal of Phosphorus from High Phosphorus Iron Ores in Wushan Mountain by Crosscurrent Acid Leaching

In the process of resource utilization of high phosphorus iron ores, phosphorus should be removed first. Compared to other dephosphorization methods, selective leaching with acid has special advantages such as high dephosphorization ratio, low iron loss and so on. However, a large amount of acidic wastewater containing phosphorus was produced after acid leaching. Therefore, the rational use of acidic wastewater and decrease of acid consumption is crucial to remove phosphorus by acid leaching. In this paper, the thermodynamics of the acid leaching was studied according to the existence form of mineral constituents in high phosphorus iron ores from Wushan Mountain. Then, crosscurrent acid leaching was employed to remove phosphorus from high phosphorus iron ores in Wushan Mountain and the changes in dephosphorization ratio, iron loss and acid concentration was observed during the leaching. The results showed that the phosphorus in Wushan iron ores could be removed selectively by acid leaching. After three-stage crosscurrent leaching, the dephosphorization ratio exceeded 74% and the iron loss was under 2.1%. Meanwhile, the acid concentration was decreased to 0.65mol/l in leaching solution, which could be returned to selective leaching after precipitation of phosphorus and supplement of hydrochloric acid.

Removal of Cd(II) Ion from Aqueous Solution by Adsorption on Wasted Low Grade Phosphorus-Containing Iron Ore

Low grade phosphorus-containing iron ore (LGPIO), a raw and wasted industrial solid material was used as an adsorbent to remove Cd(II) ion from wastewater. The effects of initial pH value, adsorptive time, initial Cd(II) ion concentration, adsorptive temperature and LGPIO dosage on the Cd(II) ion removal efficiency were studied. The results show that the Cd(II) ion removal efficiencies exceed 99.8% and Cd(II) ion concentrations are less than 0.10 mg/L under the pH value 6, temperature 20 °C, adsorptive time 90 min, initial Cd(II) ion concentration 50 mg/L, particle size <0.15 mm, adsorbent dosage 50 g/L and stirring speed 290 r/min. After Cd(II) ion removal reaction, the Cd(II) ion concentrations completely complies with the requirement of national discharge standard of water pollutants for cadmium and zinc industry (GB 20466-2010) (TCd(II) = 0.1 mg/L) in China. Therefore, it can be concluded that LGPIO is a new low-cost adsorbent which is suitable for the adsorption of Cd(II) ion from wastewater.