Study On The Removal Of Methylene Blue Wastewater Containing Copper By Wastepaper-based Double Network Hydrogel

With the improvement of people’s quality of life and the growth of people’s aesthetic needs,some heavy metal salts(e.g.,Cu²⁺,Mn²⁺,Co²⁺,Ni²⁺)are being applied more frequently as mordants in the dye industry.The mixed pollution of heavy metals and organic matter in the discharged printing and dyeing wastewater is gradually becoming more and more serious,potentially threatening the entire ecosystem down to the individual organism,so the coinstantaneous removal of heavy metals and organic matter from the wastewater by eco-efficient methods is becoming urgent.Adsorption is an economical and effective method of removing pollutants because of its low cost,ease of operation and high tolerance to toxic chemicals in water.The ideal adsorbent would be efficient,stable,cost effective,non-toxic and environmentally compatible.From the perspective of resource utilization and following the concept of“turning waste into treasure”,copper(Cu²⁺)and methylene blue（MB）were selected as the target pollutants to transform wastepaper produced in people’s daily life into a low-cost and efficient adsorbent for the treatment of heavy metals and dye wastewater.Here are the key findings in this study:（1）Wastepaper-based double network hydrogel materials（WP/PAMs）were successfully prepared by composing and gelling the wastepaper cellulose solutions with acrylamide using the sol-gel method.Comparing the adsorption effect of the WP/PAMs on Cu²⁺and MB and SEM characterisation results,the optimum wastepaper content was determined to be 2 wt%.（2）SEM,EDS,swelling ratio,thermal stability and FTIR characterisation of the2 wt%WP/PAM showed that the wastepaper and acrylamide were successfully compounded and that the prepared product exhibited excellent water absorption and thermal stability at the temperature required for this study（15-35°C）.Zata potential result revealed that the p H_PZC of the 2 wt%WP/PAM was 7.35.The p H experiment demonstrated the wide p H applicability of the WP/PAM,with acceptable removal of Cu²⁺and MB at p H 3-6 and p H 3-9 respectively.The combination of Zata potential and p H experiment revealed that electrostatic interaction was not the main mechanism for the removal of Cu²⁺and MB by the WP/PAM.（3）The kinetic and isotherm models were developed and the fitted results were analysed to find that the second-order kinetic model and the Langmuir isotherm model were more suitable for describing the adsorption behaviour of the WP/PAM on Cu²⁺and MB,indicating that the adsorption of WP/PAM on Cu²⁺and MB were chemisorption and monolayer adsorption.The Q_m values obtained from the fitted Langmuir model at 25°C were 143.6 mg/g(Cu²⁺)and 1714.5 mg/g（MB）and the fitted values were positively correlated with temperature,indicating that the reaction absorbed heat.The intraparticle diffusion model considered the adsorption between WP/PAM and Cu²⁺and MB as multi-stage adsorption and the adsorption process was co-controlled by other adsorption stages in addition to internal diffusion.The thermodynamic results confirmed the Langmuir model fitting results that the adsorption reaction of the WP/PAM on Cu²⁺and MB was not only heat absorbing,but also spontaneous.The results of the recycling experiment certified that the WP/PAM still maintained more than 80%removal of Cu²⁺and MB after six cycles,which indicated that the WP/PAM possessed stability.Analysis of the FTIR and XPS characterisation results of the WP/PAM before and after the reaction confirmed that the adsorption mechanism of Cu²⁺on the WP/PAM was related to ion exchange and complexation,while the adsorption of MB was driven by hydrogen bonding and electrostatic interactions.（4）The WP/PAM performed well in treating simulated wastewater,which indicated that the WP/PAM possessed practical application potential.Based on the recycling of wastepaper,this study provides a potential adsorbent for the treatment of dyes and heavy metal wastewater,which is important for the establishment of the concept of green development in society and the promotion of ecological environment.