Zinc Sorption on Modified Waste Poly(methyl methacrylate)

Abstract

The new one-pot hydrolysis-crosslinking reaction was used to synthesize a new, waste poly(methyl methacrylate) (PMMA)-based material for zinc(II) ions removal. The alkaline hydrolysis of PMMA in diethylene glycol diethyl ether was used to obtain polymer matrix and it was then crosslinked with Ca and Mg ions to obtain the sorbent. As a result, the macroporous materials were obtained with a yield of 87% when waste PMMA was used, and about 95% when the commercial PMMAs were used. The degree of hydrolysis was similar, from 32% to 35%. New materials were then tested for their affinity towards zinc(II) ions. Two kinetic models (pseudo-first and pseudo-second order), as well as two isotherms (Langmuir and Freundlich), were used to describe the kinetics and equilibrium of zinc(II) ion sorption on the studied materials, respectively. All the prepared PMMA-based sorbents showed similar or higher sorption capacity (q up to 87.7 mg/g) compared to commercially available materials in a broad pH range (4–7). The study shows sorption was fast—above 80% of equilibrium capacity was achieved after ca. 0.5 h. Presented results show that waste PMMA may be an interesting raw material for the preparation of sorbents for zinc(II) ions removal.

Zinc Ion Removal on Hybrid Pectin-Based Beads Containing Modified Poly(Methyl Methacrylate) Waste

“…The hybrid sorbent, similarly to pectin alone sorbent, showed very good or even greater affinity to Zn(II) ions in a broad pH range (3–6). It may be noticed that the sorption capacity of P + MPMMA did not drop significantly in pH = 3 as it was in the case of pure MPMMA material (q < 10 mg/g) [ 41 ]. Taking into account that hybrid material contained about 25% of MPMMA, the decrease in sorption capacities should be visible in pH = 3.…”

“…These values are a measure of the energy barrier during sorption, which lie in the range of the activation energy of chemisorption processes (8.4–83.7 kJ/mol) [ 49 ] . Therefore it may prove the main mechanism of sorption to be chemisorption (ion-exchange Ca 2+ –Zn 2+ ) [ 41 , 50 ].…”

“…The affinity of zinc(II) ions to hybrid sorbent is significantly higher than for pectin alone sorbent, which is reflected by higher B and K f or n value of parameters from Langmuir and Freundlich models, respectively. This is due to the MPMMA additive, which as a simple powder has greater sorption capacity as well as other sorption parameters (B, K f and n) than pectin sorbent [ 41 ]. Only sorption capacity (q m ) of P + MPMMA calculated form Langmuir isotherm is a little lower than for P sorbent, despite that the MPMMA additive as sorbent has greater sorption capacity towards Zn(II) ions (about 80 mg/g) [ 41 ], thus should enhance the q m of hybrid one.…”

“…This is due to the MPMMA additive, which as a simple powder has greater sorption capacity as well as other sorption parameters (B, K f and n) than pectin sorbent [ 41 ]. Only sorption capacity (q m ) of P + MPMMA calculated form Langmuir isotherm is a little lower than for P sorbent, despite that the MPMMA additive as sorbent has greater sorption capacity towards Zn(II) ions (about 80 mg/g) [ 41 ], thus should enhance the q m of hybrid one. It may be caused by worse fit of this model to experimental data (lower correlation coefficient: 0.973) than Freundlich one (R 2 = 0.996).…”

“…Since most of them are in the form of fine or irregular particles, their usage in column processes, as preferred in the industry, or even separation from purified solution is difficult or impossible. The same problem occurs in the case of material made from modified waste PMMA in the form of very fine powder [ 41 ]. However, despite the very good sorption capacities towards zinc(II) ions, and the proecological and economical advantage of reusing the waste materials, the sorbent form did not allow one to perform column studies.…”