| Dye wastewater has a complex composition and often contains a large amount of chemical additives.It has characteristics such as high salinity,large chroma,high BOD and COD content,therefore,its biodegradability is poor.Natural water bodies are difficult to decompose and eliminate dyes by self-purification.Hydrogels are defined as the collective name of some cross-linked polymers that are able to retain large amounts of water,while not being able to be dissolved by the above-mentioned liquids,when water or other biological fluids swell.Most hydrogels contain functional groups such as hydroxyl(-OH),amino(-NH2),carboxyl(-COOH),and amide(-CONH2),which have strong adsorption capacity for pollutants.It is a very good adsorbent.Maleic anhydride has two carboxyl groups and the hydrogel synthesized using it as a monomer can greatly increase the hydrogel adsorption capacity.Therefore,in this study,maleic anhydride(MA),acrylic acid(AA)and acrylamide(AM)were used as raw materials to prepare P(MA-co-AA-co-AM)hydrogels by aqueous solution polymerization and apply them for the adsorption of 4 kinds of cationic dyes.In this paper,the effect of synthesis conditions on the amount of dyes adsorbed on P(MA-co-AA-co-AM)hydrogels was studied.The optimal synthesis conditions were selected by orthogonal test,and the swelling properties were tested.The structure of the composite material was characterized by SEM and FTIR analysis.The effect of different conditions on the adsorption and desorption of P(MA-co-AA-co-AM)hydrogels was also studied.Adsorption kinetics and adsorption isotherms were used to study the adsorption mechanism of P(MA-co-AA-co-AM)hydrogels on dyes.The results show that:Orthogonal test results show that when the monomer ratio is(MA+AA): AM=2:1,the degree of neutralization is 70%,the amount of initiator is 0.4%,and the amount of cross-linking agent is 1.0%,P(MA-The co-AA-co-AM)hydrogel has the highest amount of dye adsorbed.The results of FTIR and SEM analysis showed that the polymerization of MA,AA,and AM monomers occurred and the P(MA-co-AA-co-AM)hydrogel was successfully synthesized.The hydrogel has a three-dimensional network.The structure,which has a large number of holes distributed on its surface,has a large specific surface area.The swelling degree of P(MA-co-AA-co-AM)hydrogel shows that the hydrogel reaches swelling equilibrium at about 12 h and the hydrogel swells at a temperature of 25°C and a p H of 8 that the degree reached the maximum.The Na+ concentration has a great influence on the swelling degree of the hydrogel.When the Na+ concentration is 6 g·L-1,the hydrogel still has a certain degree of swelling and the degree of swelling is 17.82 g·g-1.The experimental results of the adsorption of four dyes showed that the specific surface area of the hydrogel can be increased by increasing the particle size of the hydrogel.The optimum adsorption p H of the hydrogels for dyes ST,CV and MG is 3,and the optimum p H for the dye MB is 9.When the temperature range was between 25 and 35 °C,P(MA-co-AA-co-AM)hydrogel had the highest adsorption capacity for four dyes.The results of the adsorption kinetics of the four dyes on the hydrogel show that the pseudo-second-order kinetics model can be applied to the adsorption of the four dyes.Adsorption isotherm fitting results show that the fitting coefficient of the Langmuir equation to the adsorption process is greater than 0.98.Therefore,it can be inferred that the adsorption of the four dyes on the P(MA-co-AA-co-AM)hydrogel is a single molecule layer adsorption.The desorption efficiency of P(MA-co-AA-co-AM)-ST hydrogel after dye adsorption was 87%,79.16%,and 70.46%,,P(MA-co-AA-co-AM))-CV was 84.96%,70.86%,and 67.78%.The desorption efficiency of P(MA-co-AA-co-AM)-MB hydrogel cycle was 91.59%,84.13%,and 75.64%. |
PDF Full Text Request