Development Of Acid-resisting Activated Carbon Monoliths With Inorganic Cementitious Materials For Weakly Acid Water

In this paper, a new type of acid-resisting activated carbon filter for weakly acid water was made by the acidification treatment of activated carbon monoliths with inorganic cementitious materials which using granular activated carbon as main raw materials and acid-resisting inorganic cementitious materials as gelling agent. Weakly acid water was produced after filtered from the activated carbon filter and the pH value of it was controlled in a range of 4.5-6.5, which had a good effect on beauty and skincare. Compared with the electrolytic method, this method had many advantages, such as simplified equipment, low costs, low energy consumption and remaining the superior adsorption performance of harmful substance in the water.In the molding process of activated carbon filter materials, the contrastive analysis was made with acidproof cement or silicon powder using as filler. By discussing the influence of formula and curing technology on the properties, the optimal formula and prepared conditions of preparing activated carbon monoliths were decided. The microstructures of materials were characterized by XRD, BET, SEM, EDS and other analytical methods.Malic acid and citric acid were used as acidified agent in the process of activated carbon filter acidification treatment. The influence of acidification conditions on properties of water output were investigated by simulating the using process of activated carbon filter, and evaluating the pH of the outputted water and the volume of weakly acid water. The Pb2+ adsorption behaviors onto samples after acidification treatment were studied.Results from molding experiment show that activated carbon monoliths all can be prepared by using acidproof cement or silicon powder as filler, adding waterglass as binder and sodium fluorosilicate as hardener. The three compose the acid-resisting inorganic cementitious materials together. The properties of samples also are very similar, their differences mainly embody in the strength of samples, the strength of the sample with silicon powder is higher. The optimal processes of the samples by using silicon powder as filler are as follows:firstly, the mass ratio of activated carbon to cement are controlled to be 3:2, sodium fluorosilicate addition is 13wt% of waterglass; secondly, curing system is that standing in the air for 14 d and then holding in the oven for 5 h at 150℃. Finally, the corresponding properties of the optimal samples are listed below:iodine adsorption value is 318.52 mg/g, compressive strength is 6.75 MPa; water absorption is 56.45%, the porosity is 48.89%, the permeable ratio is 1000 mL/min; specific surface area is 360.18 m2/g, average pore size is 2.66 nm and pore volume is 0.21 m3/g. The pore size distribution curves show that the sample is microporous adsorbent, and the average pore size distribution of microporous ranges from 0.60 to 1.07 nm.XRD, SEM and EDS observation show that inorganic gelling agents have little effect on the pore structure of activated carbon in the samples. The more the gellants adding, the higher the compressive strength will be. The adsorption performance of the samples is proportional to the activated carbon content in the formula.The results of water output indicate that madic acid is the optimal agent for sample acidification treatment. The optimum conditions are as following: concentration is 0.7 mol/L, impregnation temperature is 60 ℃, impregnation time is 8 h, dried at room temperature, and weakly acid water yield is 6.00 L/g. Experiments of Pb2+ adsorption show that the sample still has excellent adsorption capacity after acidification treatment, the adsorption rate of Pb2+ are above 85% when the pH exceed 5.0.