The use of three freshwater microalgal culturesChlorella sorokiniana, Anabaena laxa, and Hapalosiphon welwitschii-for sorption of copper(II) from synthetic Cu (II) solutions and Marinduque, Philippines, wastewater was studied. The optimum amount of biomass for the three species was 0.025 g dry weight. The optimum contact time for both C. sorokiniana and A. laxa was 1 h, whereas that of H. welwitschii was 30 min. All three species exhibited maximum Cu(II) sorption at pH 4.0-6.0. The Langmuir adsorption isotherm was the best fit model for the three species. The three cultures were found to be effective biosorbents when used in synthetic wastewaters of low concentration (10-30 ppm). Maximum Cu(II) reductions obtained were 88.2, 88.6, and 91.7% for the C. sorokiniana, A. laxa, and H. welwitschii cultures, respectively. C. sorokiniana, A. laxa, and H. welwitschii removed 5.70, 11.16, and 7.15% of Cu(II), respectively, when applied to wastewater taken from Consolidated Mines Inc. (CMI) containing around 150 ppm Cu(II). C. sorokiniana and A. laxa, in combination, exhibited 14.05% Cu(II) removal from CMI wastewater. Desorption with 0.11 M HCl effected 73.20, 64.54, and 70.85% removal of Cu(II) from the surfaces of C. sorokiniana, A. laxa, and H. welwitschii, respectively. SEM-EDS spectra of the three species confirmed the presence of Cu(II) on their surfaces.

To treat the coking wastewater with phenolic compounds over 3000 mg/L, the biological method cannot be directly employed due to the toxicity to microorganisms and other methods are usually expensive. In this study, the aldol condensation followed by ozonation was developed to reduce the phenolic compounds in the wastewater from a coal coking plant in Gansu Province of China. For the aldol condensation reaction, the removal efficiency of phenolic compounds increases with increasing the molar ratio of formaldehyde to phenol (F/P), reaction time, reaction temperature, and acidity or alkalinity. Under alkaline conditions the removal efficiency of phenolic compounds is higher than under acid conditions. If the reaction temperature, reaction time, F/P and pH values of the aldol condensation are respectively 95°C, 3 hours, 2.0 and 10.5, the concentration of phenolic compounds decreases from 9018.3 mg/L to 1901.2 mg/L after precipitation separation of phenolic resins. Subsequently adjusting the pH value to 7 further reduces the concentration of phenolic compounds to 764.7 mg/L. Thereafter 2 hours ozonation further reduces the concentration of phenolic compounds to 22 mg/L, resulting in total removal efficiency of 99.75%. The ozonation removes phenolic compounds with methyl/ethyl substituent on benzene ring easier than phenol.