Preparation Of Coal Cinder Balls And Its Application In Water Treatment

Coal cinder is one of the solid waste. With plenty of coal cinders stacking, notonly the limited land resources was occupied, but also the environment was pollutedowing to the harmful substances the coal cinders containing. Since the coal cindershave plenty of honeycomb pores, large specific surface area, good permeability andstrong adsorption, it has been used to absorb the CODCr, ammonia nitrogen (NH4+-N),total phosphorus (TP) and suspended solids in recent years. However, if untreatedcoal cinders were directly put into the water, it will cause environmental pollutionbecause the aluminum, cadmium, copper, chromium, lead, arsenic, mercury and otherharmful metal the coal cinders contained will release to the water. Meanwhile, coalcinders were so low mechanical strength and breakage that long use of coal cinders inthe water purification process will cause the deposition of the channel and otherproblems. In order to prevent the secondary pollution of water and make full use ofcoal cinders, searching the best way of making coal cinders harmless and making highmechanical strength materials with coal cinders is particularly important in recentlyyears.Therefore, this study determine the best modified methods of making coalcinders harmless by analyzing the relationship between five different methods (1#,4mol/L HCl;2#,6mol/L HCl;3#,7.2mol/L HCl;4#,6mol/L HCl and0.05mol/LH2O2;5#,6mol/L HCl and0.1mol/LH2O2) and the concentration of harmful metals inthe leaching solution of coal cinders according to different coal cinders. At the sametime, surface characteristics and adsorption capacity of coal cinders after modificationwere studied. Then the coal cinder balls with high mechanical strength were made ofmodified coal cinders and organic bond (PVA). The modified effect of PVA wasstudied by detecting the changes of PVA with time in the process of cinder ballssoaked in the water. The adsorption ability of coal cinder balls was studied under different concentrations of CODCrand NH4+-N in the simulated water samples in thelaboratory. And when the coal cinder balls were put into the water from Liaoningprovince, the growth of biofilm in coal cinder balls were studied by SEM andmicroscope. At last, the adsorption ability of coal cinder balls to CODCrand NH4+-Nwas researched in the sink by adjusting different hydraulic retention time (HRT).The results showed that6mol/L HCl was the optimal concentration to modifythe coal cinders. After soaked by6mol/L HCl for24h, the Brunauer-Emmett-Tellersurface areas of modified coal cinders were increased. The result of SEM indicatedthe surface of modified coal cinders become more rougher, and the changes of surfacefeatures and interior structures increased adsorption capacity of modified cinders. Thedensity and hydrophilic of modified coal cinder ball were improved to some extent.And the PVA in the coal cinder balls did not nearly dissolve when the cinder ballswere soaked in the water.The adsorption ability of coal cinder balls was studied under differentconcentrations of CODCrand NH4+-N in the simulated water samples in the laboratory.The result was that the concentrations of CODCrand NH4+-N in the simulated watersamples significantly decreased. Among all of the different coal cinder balls, theCODCradsorption quantity of the coal cinder balls made of Qinghemen coal cinderswas the most,and the Qmwas about0.46mg/g. And the NH4+-N adsorption quantity ofthe coal cinder balls made of Nanpiao coal cinders was the most, and the Qmwasabout0.14mg/g). Experimental results are most interrelated with the Langmuiradsorption isotherm models and Pseudo-second-order model correlation (R>0.99).And when the coal cinder balls were put into the water from Liaoning province,the growth of biofilm in coal cinder balls were studied in the illumination incubator tosimulation environment. At the start of the study, the concentrations of CODCrandNH4+-N in water samples significantly decreased. The concentrations of CODCrdecreased to30.9mg/L from40mg/L, and the concentrations of CODCrdecreased to0.23mg/L from0.68mg/L. When the coal cinder balls soaked for23days,micro-metazoa appeared on the surface of coal cinder balls. And when the coal cinder balls soaked for28days, the dominant species on the surface of coal cinder balls wasvorticella, which marked the maturity of biological membrane.The result of coal cinder balls used to purify stream polluted water body was thatthe purification efficiency of coal cinder balls was the highest when the water inflowwas25L/h and50L/h. When the water inflow was25L/h, the removal efficiency ofcoal cinder balls on CODCrand NH4+-N was58%and57%separately. Meanwhile, theremoval efficiency of coal cinder balls on CODCrand NH4+-N was55%and50%separately, when the water inflow was50L/h.