Kong Lingwei

Phosphate removal of acid wastewater from high-phosphate hematite pickling process by in-situ self-formed dynamic membrane technology

Phosphate removal from pickling milling wastewater of high-phosphate hematite mineral by in-situ self-formed dynamic membrane reactor (DMR) developed with raw and activated red mud (RM-raw and RM-a) was studied in this paper. The results indicated that RM dosage, velocity gradient of the mixer (G value), reaction time (t), and pH were main effects on phosphate removal. The pH of the actual mineral processing wastewater is 2.50 similar to 2.53 while the phosphate concentration is 98.85 mg/l. After the treatment, the removal rate of phosphorus with RM-raw and RM-a can reach 94.33% and 99.72%, respectively, with the dosage of 23.00 g/l and 20.00 g/l, respectively. Correspondly, effluent pH was respectively 8.12 and 3.06, and both turbidity could reach the effluent requirement. Brush cleaning was a very effective cleaning method, and the membrane flux of DMR could be restored. Also, it demonstrated that acid reuse from the phosphate-contained acidic wastewater from wastewater produced in high-phosphate hematite pickling process could be achieved by in-situ self-formed dynamic membrane technology.

Phosphorus removal from domestic sewage by adsorption combined photocatalytic reduction with red mud

Phosphorus removal from domestic sewage by adsorption combined photocatalytic reduction with raw and modified red mud (RM) was studied in this paper. The results indicated that RM dosage, reaction time, stirring rate, phosphorus concentration, and initial pH of solution (pH(i)) were the main factors to effect on phosphorus removal. It was found that the phosphorus removal efficiency of modified red mud (RM-m) under the photocatalytic test conditions was higher than only by adsorption process, while raw red mud (RM-raw) showed no significant difference under the two conditions. With initial phosphorus concentration 8.26mg/L, reaction time 60min, stirring rate 200r/min, under the adsorption and photocatalytic test conditions, the optimum dosage and pH(i) of both RM-raw and RM-m were 1.8g/L and 4.0, respectively, and the corresponding phosphorus removal of RM-raw and RM-m were 90.18 and 91.70%, respectively. The optimum amount of RM-m under the two conditions were 1.6 and 1.5g/L, respectively, the optimal pH(i) 3.0, correspondingly, the phosphorus removal could reach high up to 94.30 and 99.96%, respectively.

Study of swelling-shrinkage regularity of montmorillonite crystal and its relation with matric suction

The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this paper, the actions between various interlayers of montmorillonite crystal are generally summarized as two kinds of action potentials-shrinkage potential and swelling potential. Moreover, through the experimental research and analysis, the expression formula for variations of the swelling potential and shrinkage potential with interlayer distance is presented, and the regularity of matric suction variations with interlayer distance is also obtained for unsaturated expansive soil. It may provide a new theoretical basis and research path for further research on the swelling-shrinkage mechanism of expansive soil and matric suction potential of unsaturated soil.The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this paper, the actions between various interlayers of montmorillonite crystal are generally summarized as two kinds of action potentials-shrinkage potential and swelling potential. Moreover, through the experimental research and analysis, the expression formula for variations of the swelling potential and shrinkage potential with interlayer distance is presented, and the regularity of matric suction variations with interlayer distance is also obtained for unsaturated expansive soil. It may provide a new theoretical basis and research path for further research on the swelling-shrinkage mechanism of expansive soil and matric suction potential of unsaturated soil.

A comparative study on the enhanced operation of a BFB and SFCW coupling process for domestic wastewater treatment

In this study, a new coupling process system of BFB (biological filter bed) and SFCW (subsurface-flow constructed wetland) based on the auto-ventilation network was proposed, and the comparative pollutant removal efficiency of the pilot test coupling system with different substrates configurations were investigated. The study found that: the influent concentration of the system fluctuated greatly and effluent concentration of the comparison system (b) was 20.22 ± 13.37 mg/L, 2.70 ± 2.49 mg/L, 4.40 ± 3.05 mg/L and 1.09 ± 0.62 mg/L, respectively. The comparison system (b) had better removal rates than that of the original system (a), which was 81.30 %, 90.28 %, 88.57 % and 75.36 % for CODcr, NH4 +-N, TN and TP, respectively. The removal of the above main water indexes of the comparison system (b) promoted to 4.20 %, 9.20 %, 7.66 % and 13.61 % respectively when compared to the original system (a), which showed that the optimized configuration of various kinds of substrates was significant and was more beneficial to the degradation and removal of pollutants. The adsorption and interception function of substrates in the constructed wetland was the main way of phosphorus removal. The function of auto-ventilation ensured the amount of DO in the coupling system, making the phosphorus removal was less affected comparing to structure of traditional wetland.

Experimental investigation on relative contribution of hot and humid weather and heavy rainfall in disintegration of basalt residual soil

Basalt residual soil presents strong disintegration phenomenon by climatic influence. In order to understand the relative contribution on hot and humid weather and frequent heavy rainfall in disintegration of basalt residual soil, basalt residual soils were first subjected to wetting-drying cycles, and then were used for disintegration test in atmosphere and in soaking to simulate the effect of the climate change, based on a series of indexes such as disintegration rate, disintegration velocity and disintegrative deposits characteristics. The results showed that hot and humid weather could damage the aggregation between particles and facilitated the dispersibility of soil, and the majority of disintegrative deposits translate from coarse to fine, which in turn may lead to severe disintegration. While sudden heavy rain contributed to more severe disintegration, and with the increment of wetting-drying cycles, disintegrative deposits turn from lump or fragment to powder, and translate to mud, disintegration velocity increases and disintegration tends to a more severe extent. Based on the experimental findings, a disintegration classification for basalt residual soil is suggested in order to determine and evaluate disintegration characteristics according to the laboratory test results.

Research on variability characteristics of micropore of Zhanjiang clay under ambient temperature and pressure, normal atmospheric

Soils are generally used as building material and foundation, are normally under the atmospheric with ambient temperature and pressure, nevertheless, effect of oxidation of soil proceeding so slowly that it is no easy to perceive, long-term deterioration of soil properties, cannot be ignored. Zhanjiang Clay was taken as the object of study, studied the reformation effect on the micro-structures under the influence of the atmospheric and its impacting mechanism to soil properties, by scanning electron microscopy, mercury intrusion porosimetry and nitrogen absorption method. Research shows, after oxidized, the color of soil changes from grayish green and light grayish green to yellow and yellowish brown; while aggregation of soil particles increases, not only Swelling-shrinkage properties, but also plasticity of soil particles decreases, as for the sensitivity and structure yield strength reduced. Furthermore, atmospheric environment has an effect of shrinkage and closure on pores ( d d >1 μm), which results in a decrease of total pores volume of oxidized clay. As far as pores ( d >1 μm) are concerned, pores volume increases remarking, with appearance of fracture porosity and reduction of ink-bottle type pores, as well as conversion from open pores to close ones. The transformation of soil properties by the influence of atmospheric is not caused by inherent changes of mineral, but the remodeling effect of micro-structures because of motion effects and chemical reactions of water-soil-electrolytes- atmosphere leading to coupling and transforming of soil particles. It is the variation of ultra-micro-structure that generates this phenomenon. Prolonged influence with comparatively large potential harmful impact on soil stability caused by damage effects on structural strength during oxidation, it turns out to be necessary to strengthen monitoring the effect on geotechnical engineering of physical and chemical factors in environment.