A review of the existing and emerging technologies for wastewaters containing tetramethyl ammonium hydroxide (TMAH) and waste management systems in micro-chip microelectronic industries

The present work aims to describe and review the available technologies and the recent advancements in treating industrial wastewater containing tetramethylammonium hydroxide (TMAH). It is a quaternary ammonium salt and widely used in the microelectronics industry; this kind of company produces large quantities of wastewater containing TMAH. The exhausted solutions must be treated appropriately since TMAH is corrosive, toxic to human health, and ecotoxic. Regarding the concentration at discharge, currently there are no European regulations. Still, it has been indicated that the substance has a negative influence on the oxygen balance and cause eutrophication, and fall into the relevant categories. In the first part of the work, the available technologies and the recent advancements for the treatment of TMAH contained in industrial wastewater are reviewed. Separation methods as such adsorption, ion exchange, membrane processes, and destruction technologies classified as advanced oxidation processes and biological processes have been considered. In the second part of the manuscript, industrial patented wastewater treatments have been described. Biological processes are those more used, being more economically feasible, require very long times not always sustainable.

HEAVY METAL REMOVAL BY CELLULOSE-BASED TEXTILE WASTE PRODUCT

The textile industry is a source of significant amounts of cellulosic waste that can be processed into promising sorbents. The aim of study was understanding the adsorption behavior of metal ions on cellulose surfaces obtained from cellulose textile waste of light industry. Previous studies have shown that unmodified cellulose-based ion exchange resins obtained at different pH values were able to remove metal ions from aqueous solution. In present work the cellulose-based ion exchange resins were prepared by H2SO4 hydrolysis of initial waste product with following neutralization up to different pH and drying at 80 °C. Based on the fractional composition of powdered sorbents, the weighted average particle size of the sorbents used is determined: sorbents with pH = 1.5 - 3 ≈ 0.57 mm; sorbents with pH = 5 - 7 ≈ 0.14 mm. The IR analysis of the elemental composition of the particles showed the presence of bound sulfate groups in the powder sorbent with pH = 1.5-3. The results of experiments showed that the modification of the surface of the cellulose waste with sulfuric acid increased the effect of adsorption of Ni, Fe and Pb ions from an aqueous solution. It has been established that the electrostatic interaction between surface functional groups plays a significant role in the adsorption properties of the sorbents obtained. The affinity of sulphonic acid resins for cations generally varies with the ionic size and charge of the cation. This study showed that adsorption capacities of studied metals were in the order of Fe3+<Pb2+<Ni2+. Resulting cellulose particles have sulfate groups on their surface, which have wide range of applications for the removal of heavy metal ions from wastewater.