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A B S T R A C TSeawater desalination by reverse osmosis (RO) invokes the necessity of brine disposal. On the other hand, the chlor-alkali industry requires saturated brine with a low content of calcium and magnesium contaminations. This paper describes a preliminary study exploring the possibility of the application of RO, nanofiltration-reverse osmosis, and nanofiltrationreverse osmosis-multieffect distillation seawater desalination brines as a sodium chloride source for membrane electrolysis. A concept has been proposed in which electrodialysis with univalent permselective membranes is used to enrich chlor-alkali lean brine with sodium chloride, and simultaneously desalinate discharge brine. The experiments with an electrodialyzer equipped with Neosepta Ò ACS and CMS membranes of 42 cm effective length have shown that the desired concentration of membrane electrolysis feed (above 300 g/L as NaCl) can be achieved. At the same time, the concentrations of both calcium and magnesium are decreased, the latter to a greater extent, that facilitates the successive brine purification step.

Hybrid and integrated membrane systems are often proposed as a way to increase the water recovery in desalination plants. Four different configurations of seawater desalination plants were compared: a standard single-stage seawater reverse osmosis (SWRO), a hybrid SWRO-electrodialysis (ED) system, a nanofiltration (NF)-SWRO system, and an NF-SWRO-ED. Based on the laboratory results, the overall water recovery, energy consumption, scaling risk, and the composition of the generated waste brine were projected. An NF-SWRO-ED system was found as the best choice. The proposed system is able to produce highly concentrated brine, close to saturation with respect to sodium chloride. The brine can be further used in evaporated salt production or in the chlor-alkali industry.

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.