Preparation of MnO_2 and calcium silicate hydrate from electrolytic manganese residue and evaluation of adsorption properties

Electrolytic manganese residue(EMR), a high volume byproduct resulting from the electrolytic manganese industry, was used as a cheap and abundant chemical source for preparing MnO2 and EMR-made calcium silicate hydrate(EMR-CSH). The MnO2 is successfully synthesized from the metal cations extracted from EMR, which can effectively recycle the manganese in the EMR. By the combination of XRD, SEM and EDX analysis, the as-prepared MnO2 is found to exhibit a single-phase with the purity of 90.3%. Furthermore, EMR-CSH is synthesized from EMR via hydrothermal method. Based on the detailed analyses using XRD, FT-IR, FE-SEM, EDX and BET surface area measurement, the product synthesized under the optimum conditions(p H 12.0 and 100 °C) is identified to be a calcium silicate hydrate with a specific surface area of 205 m2/g incorporating the slag-derived metals(Al and Mg) in its structure. The as-synthesized material shows good adsorption properties for removal of Mn2+ and phosphate ions diluted in water, making it a promising candidate for efficient bulk wastewater treatment. This conversion process, which enables us to fabricate two different kinds of valuable materials from EMR at low cost and through convenient preparation steps, is surely beneficial from the viewpoint of the chemical and economical use of EMR.

Transport hindrances with electrodialytic recovery of citric acid from solution of strong electrolytes

Electrodialytic （ED） recovery of citric acid （CA） in the presence/absence of strong electrolytes （NaCl, CaCl2 and Feel3） was separately analyzed under different process conditions. Recovery effectiveness was quantitatively estimated from current efficiency values. Efficiency attained optimum value with both flow rate and potential applied, while a monotonic rise was noted with temperature which got lowered beyond 0.1 tool. L 1 feed concentration. 40% drop in efficiency was recorded in the presence of strong electrolytes （Noel, CaCl2 and Feel3） in feed relative to their presence in concentrate. Severe transport hindrance and efficiency loss were attributed to adsorption and allied physicochemical changes occurred with anion/cation exchange membranes （AEM/CEM） and these were confirmed through contact angle/Chronopotentiometry/AFM/EDX. Sluggish potential rise （Galvanostatic mode） in Chronopotentiometric analysis indicated diffusion limiting transport of organic acids influenced AEM resistance. XRD and EDX analysis indicated the presence of salt hydrates/ions （Ca2＋/Fe3＋） over CEM justifying the resistance buildup due to adsorption of multivalent metal ion（s） and salts.