Preparation of Mn/Ti-modified zeolite and its performance for removing iron and manganese

Excessive iron and manganese presented in groundwater sources may cause harm to human health that needs to be solved urgently. This research aims to develop high-performance Mn/Ti-modified zeolites using sol-gel method and hydrothermal synthesis method to remove Fe²⁺ and Mn²⁺ simultaneously. The preparation parameters were optimized by response surface methodology, and the results confirmed that the optimal preparation conditions were as follows: mass ratio of MnO₂-TiO₂/zeolite = 1, hydrothermal temperature = 200°C, and calcination temperature = 500°C. The results of batch adsorption experiments showed that the best removal rate of Fe²⁺ and Mn²⁺ by modified zeolite materials which was prepared under the optimum conditions reached 96.8% and 94.4%, respectively, at which the saturated adsorption capacity was 2.80 mg/g and 1.86 mg/g. Through the adsorption kinetics, thermodynamics, internal diffusion, and isothermal adsorption analyses, it is confirmed that the adsorption process of Fe²⁺ and Mn²⁺ by the modified zeolite is mainly chemical adsorption. The results of the Weber-Morris internal diffusion model prove that internal diffusion is not the only step that controls the adsorption process. In addition, combined with the characterization of the composite-modified zeolite and the adsorption experimental study, it shows that there is an autocatalytic reaction in the adsorption process.

Simultaneous removal of cationic and anionic heavy metal contaminants from electroplating effluent by hydrotalcite adsorbent with disulfide (S2-) intercalation

Hydrotalcite materials are generally utilized for anionic pollutants due to its interlayered anion exchange ability. Their potentiality for cationic contaminants is rarely explored. In this study, disulfide (S^2-) intercalated LDH material demonstrated capability to remove both heavy metal cations and oxyanions simultaneously from water. The S^2- intercalation of LDH significantly improved its adsorption capability towards both heavy metal cations (Co²⁺ and Ni²⁺) and oxyanion (CrO₄^2-). The adsorption amount of S-LDH towards Co²⁺ and Ni²⁺ reached 88.6mg/g and 76.2mg/g, which are 405% and 281% higher than that of pristine LDH. For CrO₄^2- removal, the adsorption amount reached 34.7mg/g, 402% higher than that of pristine LDH. The cations capture mechanism mainly depends on the novel layer sheet cation substitution mechanism based on irreversible precipitation and the generation of metal sulfide precipitates. Meanwhile, the interlayered S^2- can be easily replaced by CrO₄^2- to realize the simultaneous removal of both heavy metal cations and oxyanions. In the fixed-bed column experiments, 448 bed volume (BV) (672 mL) of simulating electroplating wastewater can be efficiently treated by yielding only 1 BV(15 mL) of chemical sludge, which is practically acceptable. This work provided a highly practical adsorption technology based on the S^2- modification hydrotalcite material for the purification of heavy metal ions contaminated wastewater.

A study on cations and color removal from thin sugar juice by modified sugar beet pulp

This article describes the use of citric acid modified sugar beet pulp as new ion-exchanger sorbent for the removal of metal cations and colorants from thin juice. The results of batch adsorption runs concerning the effects of contact time, material dosage, temperature and pH drop were presented and discussed. Experimental data on the removal of metal cations showed that the sorption process was rapid and reached equilibrium in 60 min. Modified material in acidic form caused to a significant pH drop in thin juice, which could result with sucrose inversion. Uptake of metal cations increased with temperature whereas that of color decreased. Neutralised type modified product gave more satisfying results. After six successive contacts, 49.7%, 37.5% and 43.7% removals for Ca-Mg, K and color, respectively, were obtained by using neutralised form of modified sugar beet pulp.