The potential of quaternized rice hulls in removing Cr(VI) from synthetic solution, chrome electroplating waste and wood preservative waste was investigated in column experiments. Increase in column bed depth resulted in a longer service time at C(t)/C0 = 0.5 breakthrough. The presence of SO2−4, which is commonly present in the wastes, interfered with the sorption process and resulted in earlier breakthrough. The sorption process was flow-rate independent within the scope of this study. In the regeneration study, Cr(VI) could be recovered almost quantitatively by eluting with a 0.5 M NaOH solution and the column could be used repeatedly for at least five cycles.
This annual review covers the literature published in 2018 on topics related to the occurrence and fate of environmental pollutants in wastewater. Due to the vast amount of literature published on this topic, we have discussed only a portion of the quality research publications, due to the limitation of space. The abstract search was carried out using Web of Science, and the abstracts were selected based on their relevance. In a few cases, full‐text articles were referred to understand new findings better. This review is divided into the following sections: antibiotic‐resistant bacteria (ARBs) and antibiotic‐resistant genes (ARGs), disinfection by‐products (DBPs), drugs of abuse (DoAs), estrogens, heavy metals, microplastics, per‐ and polyfluoroalkyl compounds (PFAS), pesticides, and pharmaceuticals and personal care products (PPCPs), with the addition of two new classes of pollutants to previous years (DoAs and PFAS).
The potential of the biomass of non-living water hyacinth roots Eichhornia crassipes, as a biosorbent for Cr(VI) from synthetic solution and electroplating waste was investigated under batch conditions. Various factors affecting sorption of chromium were studied. They include effect of pH, initial concentration, dosage, agitation rate, temperature and the presence of other anions. The optimum pH for the sorption was found to be 2.0 and sorption decreased rapidly as the pH of the solution was increased. Data obtained from sorption isotherms conformed to Langmuir sorption model which implied a monolayer coverage and the maximum sorption capacities of Cr(VI) were 8.93 and 8.92 mg/g for synthetic solution and electroplating waste respectively. A continuous flow study showed that water hyacinth root was effective in removing Cr(VI) from electroplating waste.
The sorption of Cr(VI) from synthetic solution and electroplating waste by quaternized rice hulls was investigated under laboratory conditions to assess its potential in removing Cr(VI). The results show that quaternized rice hulls provided higher sorption capacity and a more workable pH range as compared to the untreated rice hulls. From the Langmuir isotherm the maximum sorption capacity of Cr(VI) was 32.3 mg/g at pH 4.82 at 25°C. Column studies showed that Cr(VI) and Cu(ll) from electroplating waste could be successfully removed or reduced using a combination of untreated and quaternized rice hulls. The effect of different anions on the sorption capacity of quarternized rice hulls was discussed.
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