In this research, the potential of chitosan to be used as a coagulant to treat coal wastewater was investigated, in comparison to a conventional coagulant, i.e: Al2(SO4)3 or aluminum sulfate, and Poly Aluminium Chloride (PAC). The parameters being studied were turbidity, pH, TDS, and TSS. The result of this research showed that chitosan worked as a more efficient coagulant to treat coal wastewater compared to alum and PAC, in terms of the needed dose of application. The optimum dose of chitosan was 20 mg/L that gave a 100% decrease in turbidity and TSS. On the other hand, a dose of 120 mg/L of alum was needed to have an optimum result, where the turbidity and TSS were decreased up to 100%. When PAC was used as a coagulant, the optimum dose was 120 ppm that reduced turbidity and TSS to 99.50% and 99.58%, respectively. Coagulation by chitosan, alum, and PAC were all influenced by pH, where the optimum pH for all three coagulants was within a range of neutral pH.

The objective of this work was to evaluate the chemical composition of essential oil from Varronia curassavica Jacq. obtained by microwave (MI) and hydrodistillation (HD) extraction methods. The MI method tested three powers (500, 600, and 700W), three distillation times (20, 30, and 40 min.), and three water volumes (0, 25, and 50 mL per sample). The HD method tested three distillation times (100, 120, and 140 min.) and three water volumes (1.0, 1.5, and 2.0 L per 3-liter flask). The essential oils were analyzed by GC/MS-FID. The optimal condition for the essential oil extraction by the MI method was 700W for 40 min. (3.28%), regardless of the volume of water. In its turn, the best condition for essential oil extraction by the HD method was 120 min. with 1.0 L of water per flask (3.34%). The most abundant compounds for MI (700 W for 40 min. without water) were shyobunol (26.53%) and bicyclogermacrene (4.96%); and the most abundant compounds for HD (120 min. with 1.0 L of water/flask) were shyobunol (24.00%) and germacrene D-4-ol (10.23%). Methyl farnesoate (2E, 6E) and farnesyl acetate (2Z, 6E) were not detected in the essential oil extracted by HD; however, they were identified by the MI method. By increasing the distillation time and/or volume of water in HD, a reduction was observed for the content of the chemical compounds β-elemene (from 1.23 to 0.97%), Ecaryophyllene (from 5.49 to 4.35%), α-humulene (from 1.80 to 1.43%), alloaromadendrene (from 1.78 to 1.44%), bicyclogermacrene (from 5.63 to 4.55%), and germacrene D-4-ol (from 11.40 to 9.86%). Power, extraction time, and their interactions influenced the content of essential oil obtained by microwave extraction (MI). Within each power, the highest essential oil content was extracted at the longest distillation time (40 min.), except for 600W, where no significant difference was detected between 30 and 40 min. The optimal essential oil contents for both extraction methods were statically similar by the t-test for dependent samples. However, the MI method presents advantages, such as shorter distillation time and less energy and water consumption.