Highly Effective Removal of Toxic Cr(VI) from Wastewater Using Sulfuric Acid-Modified Avocado Seed

Abstract

Sulfuric acid modified avocado seed (ASSA), as a low-cost carbonized adsorbent, was investigated for the removal of toxic Cr(VI) from water/wastewater in batch experiments. A low temperature (100 °C) chemical carbonization treatment was employed for the production of the adsorbent. FE-SEM and HR-TEM images revealed the formation of agglomerated and rodlike structured particles after carbonization of avocado seed. BET and TGA analyses of ASSA demonstrated its mesoporous structure and thermal stability up to 200 °C. The presence of oxo-functional groups on the ASSA surface was confirmed by ATR-FTIR and XPS studies. Adsorption of Cr(VI) onto ASSA was highly pH dependent and found to be an optimum at pH 2.0. Adsorption isotherm results suggested that the capacity increases with an increase in temperature. Nonlinear regression analysis revealed that the Freundlich isotherm model provides a better correlation than the Langmuir isotherm model for Cr(VI) adsorption onto ASSA. The maximum Cr(VI) adsorption capacity of 333.33 mg/g was obtained at 25 °C, which is higher than most of the previously reported carbonized adsorbents used for Cr(VI) removal. Adsorption kinetics was best described by the pseudo-second-order model. The presence of coexisting ions slightly affected the Cr(VI) removal efficiency of ASSA. Experiment with real wastewater sample containing 47.34 mg/L of Cr(VI) demonstrated that by the use of only 0.03 g/25 mL of ASSA, almost 100% removal was achieved at pH 2.0, which suggests its potential application in wastewater treatment plants. The ASSA retained its original Cr(VI) sorption capacity up to three consecutive adsorption–desorption cycles. Finally, from XPS analysis, electrostatic attraction of Cr(VI) species to the adsorbent and its subsequent reduction to Cr(III) were identified as the leading removal mechanisms.

Facile preparation of hybrid porous polyanilines for highly efficient Cr(vi) removal

“…Furthermore, SO 4 2À ions decrease the surface positive charge and thereby decrease the electrostatic interactions between the surface and the Cr(VI) species. 68 Generally, regardless of the presence of these coexisting cations and anions, the equilibrium adsorption amounts for Cr(VI) were all greater than 920 mg g À1 ; these results indicate that the affinity between Cr(VI) and LHPP-1 is very strong and Reusability of the adsorbent. Adsorption-desorption experiments were conducted for four cycles to verify the reusability of the LHPPs.…”

Avocado (Persea americana Mill.) by‐products and their impact: from bioactive compounds to biomass energy and sorbent material for removing contaminants. A review

“…Similar capacity was demonstrated by another carbonised adsorbent constituted of sulphuric acid modified avocado seeds for the removal of Cr(VI). Cr(VI) adsorption onto the sorbent was highly pH dependent, reaching the best capacity at pH 2.0 and increases with temperature (Bhaumik et al ., ).…”

Pengaruh Aktivator Terhadap Kemampuan Bubuk Biji Alpukat (Persea americana Mill) dalam Menjerap Ion Timbal (II)

“…Diantara metode tersebut, adsorpsi merupakan teknik yang paling sering digunakan karena murah, mudah, ramah lingkungan dan memiliki efisiensi yang tinggi untuk menghilangkan logam berat (Bhaumik et al 2014;Ramírez-Montoya et al 2014). Pada penelitian ini akan digunakan biji alpukat sebagai adsorben ion Pb(II) dalam larutan.…”

“…Pada penelitian Elizalde-González et al (2007), adsorben biji alpukat yang dipreparasi dengan cara karbonisasi pada temperatur 800°C dan 1000°C serta diaktivasi menggunakan H 3 PO 4 mempunyai luas permukaan 1802 m 2 /g dan 452 m 2 /g. Selain itu, pada penelitian Bhaumik et al (2014) dinyatakan bahwa sebanyak 0,08 g bubuk biji alpukat yang memiliki efisiensi penjerapan ion Cr(VI) sebesar 99,95%. Penelitian Rodrigues et al (2011) menyatakan bahwa arang aktif biji alpukat yang diaktivasi secara fisika dapat diaplikasikan untuk menyerap fenol dengan kapasitas adsorpsi sebesar 90 mg/g.…”

“…Kandungan air pada penelitian ini tidak berbeda jauh dengan kandungan air yang diperoleh oleh Malangngi dkk. (2012) yaitu 12,86%, sedangkan untuk kandungan abu mempunyai hasil yang berbeda dengan yang dilakukan oleh (Bhaumik et al 2014) yaitu 0,22%. Hasil karakterisasi kandungan air dan kandungan abu didukung oleh besarnya daya adsorpsi bubuk biji alpukat yang diaktivasi dengan larutan HCl 5,0% terhadap iodium yaitu 823,71 mg/g dan luas permukaan yaitu 86,94 m2/g.…”