PRESIPITASI LOGAM BERAT LIMBAH CAIR LABORATORIUM MENGGUNAKAN NATRIUM SULFIDA DARI BELERANG ALAM

Precipitation of Laboratory Wastewater Heavy Metals by Natural Sulphur Sodium Sulfide Sodium sulfide (Na2S) from natural sulfur has been used for heavy metal precipitation from laboratory wastewater. Heavy metals in laboratory wastewater include mercury (Hg), lead (Pb), chromium (Cr) and zinc (Zn). Initial laboratory wastewater testing was performed by measuring the initial pH and the concentration of heavy metals in the wastewater prior to precipitation using the atomic absorption spectrophotometer. Sulphide precipitation phase consists of variations in the concentration of NaOH, time, temperature, and volume of dissolving Na2S. Parameters for the efficiency of Hg, Pb, Zn and Cr heavy metal precipitation were the initial pH, concentration and rate of stirring of the solution. Results showed that the optimum precipitation efficiency for Zn is achieved by using 10 % Na2S solution with an efficiency of 97.93 %. The most significant reduction in Cr and Hg was the use of 20 % Na2S solution with a precipitation efficiency of 99.24 % and 99.76 % respectively. The optimal efficiency for Pb with a 30 % Na2S solution was 99.68 %. Natural sulfur can reduce the levels of heavy metals in laboratory wastewater by precipitation.Key words: Natural sulfur, Heavy metals, Precipitation, Sodium sulfide, ABSTRAKPresipitasi logam berat dari limbah cair laboratorium telah dilakukan dengan menggunakan natrium sulfida (Na2S) dari belerang alam. Logam berat yang terkandung dalam limbah cair laboratorium diantaranya adalah merkuri (Hg), timbal (Pb), kromium (Cr) dan seng (Zn). Pengujian awal limbah laboratorium dilakukan dengan mengukur pH awal dan kadar logam berat yang terdapat dalam limbah sebelum presipitasi menggunakan pH meter dan spektrofotometer serapan atom. Tahapan presipitasi limbah oleh sulfida meliputi pembuatan variasi konsentrasi NaOH, waktu, suhu, dan volume pelarutan Na2S. Parameter efisiensi presipitasi logam Hg, Pb, Zn, dan Cr meliputi pH, Konsentrasi dan Kecepatan pengadukan. Hasil penelitian menunjukkan efisiensi pengendapan optimal untuk logam Zn terdapat pada penggunaan larutan Na2S 10% dengan efisiensi 97,93%. Larutan Na2S 20% paling banyak menurunkan logam Cr dan Hg dengan efisiensi masing-masing sebesar 99,24% dan99,76%. Efisiensi optimal untuk logam Pb berada pada penggunaan larutan Na2S 30% dengan efisiensi 99,68%. Belerang alam mampu menurunkan kadar logam berat dalam limbah cair laboratorium dengan metode presipitasi.Kata kunci: Belerang alam, Logam berat, Presipitasi, Natrium sulfida

Removal of Metals by Sulphide Precipitation Using Na2S and HS−-Solution

Precipitation of metals as metal sulphides is a practical way to recover metals from mine water. Sulphide precipitation is useful since many metals are very sparingly soluble as sulphides. Precipitation is also pH dependent. This article investigates the precipitation of metals individually as sulphides and assesses which metals are precipitated as metal hydroxides by adjustment of the pH. The precipitation of different metals as sulphides was studied to determine the conditions under which the HS− solution from the sulphate reduction reaction could be used for precipitation. H2S gas and ionic HS− produced during anaerobic treatment could be recycled from the process to precipitate metals in acidic mine drainage (AMD) prior to anaerobic treatment (Biological sulphate reduction), thereby recovering several metals. Precipitation of metals with HS− was fast and produced fine precipitates. The pH of acid mine water is about 2–4, and it can be adjusted to pH 5.5 before sulphide precipitation, while the precipitation, on the other hand, requires a sulphide solution with pH at 8 and the sulphide in HS− form. This prevents H2S formation and mitigates the risk posed from the evaporation of toxic hydrogen sulphur gas. This is a lower increase than is required for hydroxide precipitation, in which pH is typically raised to approximately nine. After precipitation, metal concentrations ranged from 1 to 30 μg/L.

Origin of the Fule Pb–Zn deposit, Yunnan Province, SW China: insight from in situ S isotope analysis by NanoSIMS

The Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province is one of the most productive areas of Pb–Zn resources in China. The Fule deposit occurs in Permian carbonate and contains Pb–Zn reserves exceeding 1 Mt. To investigate the sulphur source, in situ S isotopic analysis of sphalerite and pyrite was carried out using nanoscale secondary-ion mass spectrometry. The results show that the δ34S values of the sulphide minerals range from +16.1‰ to +23.0‰, higher than that of marine sulphates hosted in Permian carbonate rocks (+11‰), but similar to that of sulphates over a broader area (+12.9‰ to +25.9‰). The sulphates in the regional rocks could therefore represent an important source of S for the Fule deposit via thermochemical sulphate reduction. The S source of the Fule deposit is different from those of most other Pb–Zn deposits in the SYG Pb–Zn mineralization province, which were mainly derived from the ore-bearing strata. The δ34S values of the early to late generations and some single sulphide crystals from the cores to rims show a slight increasing trend, implying that partial Rayleigh fractionation took place in the Fule deposit. It is suggested that the Fule sulphide precipitation resulted from the mixing of a metalliferous fluid with a H2S-rich fluid derived from the regional strata. Combining the geology, mineralogy and S isotope results with previous Pb isotope studies, it is suggested that the Fule deposit should be attributed to a Mississippi Valley type deposit.

Glaucony authigenesis, maturity and alteration in the Weddell Sea: An indicator of paleoenvironmental conditions before the onset of Antarctic glaciation

Three types of glaucony grains were identified in the late Eocene (~35.5–34.1 Ma) sediments from Ocean Drilling Program (ODP) Hole 696B in the northwestern Weddell Sea (Antarctica). The grains are K2O-rich (~7 wt%) and formed by smectite-poor interstratified ~10 Å glauconite-smectite with flaky/rosette-shaped surface nanostructures. Two glaucony types reflect an evolved (types 1 and 2 glaucony; less mature to mature) stage and long term glauconitization, attesting to the glaucony grains being formed in situ, whereas the third type (type 3 glaucony) shows evidences of alteration and reworking from nearby areas. Conditions for the glaucony authigenesis occurred in an open-shelf environment deeper than 50 m, under sub-oxic conditions near the sediment-water interface. These environmental conditions were triggered by low sedimentation rates and recurrent winnowing action by bottom-currents, leading to stratigraphic condensation. The condensed glaucony-bearing section provides an overview of continuous sea-level rise conditions pre-dating the onset of Antarctic glaciation during the Eocene-Oligocene transition. Sediment burial, drop of O2 levels, and ongoing reducing (postoxic to sulphidic) conditions at Hole 696B, resulting in iron-sulphide precipitation, were a key limiting factor for the glauconitization by sequestration of Fe2+.

Recovery Ion Hg2+ dari Limbah Cair Industri Penambangan Emas Rakyat dengan Metode Presipitasi Sulfida dan Hidroksida

Unlicensed gold mining activities (PETI) using mercury (Hg) as a gold element binder is called the amalgamation process. Mercury is a heavy metal toxic. The use of mercury can potentially cause pollution in environment, especially the aquatic environment. For overcoming the heavy metals mercury in liquid waste, it needs an alternative wastewater treatment method called chemical precipitation. This study is aimed to recover Hg2+ ions from liquid wastes by using sulphide precipitation and hydroxide methods. This research studied the effect of pH on Hg ions which is deposited in the precipitation process and found out the rate of Hg precipitation formation. Precipitation was done by using sodium sulphide (Na2S) 0.3 M and Ca(OH)2 0.004 M as a precipitation agent with rapid mixing speed for about 200 rpm for 3 minutes and continued with slow mixing for about 40 rpm for 30 minutes. Then, just let the liquid sample be for 24 hours to precipate the precipitate formed. The results show that precipitation method by using a Na2S solution can decrease the content of Hg in HgCl2 synthetic waste. An optimum mass of HgS precipitate of 0,0458 g was achieved pH 9 for 200 mL of wastewater liquid with a removal efficiency percentage up to 99.81%. The concentration of mercury can be derived from 130 ppm to 0.25 ppm. The rate of formation of HgS precipitate was obtained 0.0004g/ hour. While, hydroxide precipitation method can decrease mercury level up to 90,11% at pH 12 and mass of Hg (OH)2 precipitate obtained is 0,2784 g. However, the result of EDX analysis of the precipitate of Hg (OH)2 shows that the content of Hg precipitate is just 0.281%.