A functionalized activated carbon adsorbent prepared from waste amidoxime resin by modifying with H_(3)PO_(4) and ZnCl_(2) and its excellent Cr(Ⅵ)adsorption

With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(Ⅵ). The waste amidoxime resin was first modified with H3PO4 and ZnCl_(2), and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(Ⅵ) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(Ⅵ) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(Ⅵ) to Cr(Ⅲ) and decrease the toxicity of Cr(Ⅵ) during adsorption. PPR-Z exhibited Cr(Ⅵ) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(Ⅵ) adsorption are the chemical reduction of Cr(Ⅵ) into Cr(Ⅲ) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(Ⅵ) pollution and realizes the concept of “treating waste with waste”.

Treatment of electroplating wastewater

To study the feasibility of treated water being used as rinsing water with CP/ED (chemical precipitation/ electrodialysis) system, the relation between concentration of Cr (Ⅵ) and conductivity of water is investigated, the effect of electrodialysis (ED) for different wastewater is also studied. And several parameters of importance that are relevant to the process are identified. Analysis of ICP (Inductively coupled plasma) and IC (Ion chromatography) shows that the main reason of conductivity increase in CP treated water is the increase of Na+ and Cl- ions. The 93.8%-100% of ions from wastewater both in ED and CP/ED systems was removed successfully. The results of experiments indicate that the CP/ED system is a feasible method for electroplating wastewater treatment, the CP/ED system used as a way of wastwater is not only in favour of environment, but also economic beneficial to achieve.

Recovery of Ni(Ⅱ)from real electroplating wastewater using fixed-bed resin adsorption and subsequent electrodeposition

Effective recovery of high-value heavy metals from electroplating wastewater is of great significance,but recovering nickel ions from real electroplating wastewater as nickel sheet has not been reported.In this study,the pilot-scale fixed-bed resin adsorption was conducted to recover Ni(Ⅱ)ions from real nickel plating wastewater,and then the concentrated Ni(Ⅱ)ions in the regenerated solution were reduced to nickel sheet via electrodeposition.A commercial cation-exchange resin was selected and the optimal resin adsorption and regeneration conditions were investigated.The resin exhibited an adsorption capacity of 63 mg/g for Ni(Ⅱ)ions,and the average amount of treated water was 84.6 bed volumes(BV)in the pilot-scale experiments.After the adsorption by two ion-exchange resin columns in series and one chelating resin column,the concentrations of Ni(Ⅱ)in the treated wastewater were below 0.1 mg/L.After the regeneration of the spent resin using 3 BVof 4%(w/w)HC1 solution,1.5 BV of concentrated neutral nickel solution(>30 g/L)was obtained and used in the subsequent electrodeposition process.Using the aeration method,alkali and water required in resin activation process were greatly reduced to 2 BV and 3 BV,respectively.Under the optimal electrodeposition conditions,95.6%of Ni(Ⅱ)in desorption eluent could be recovered as the elemental nickel on the cathode,llie total treatment cost for the resin adsorption and regeneration as well as the electrodeposition was calculated.