Removal of Cadmium and Chromium by Mixture of Silver Nanoparticles and Nano-Fibrillated Cellulose Isolated from Waste Peels of Citrus Sinensis.

Neha Tavker,Arun Kumar Shukla,Javed Alam,Virendra Kumar Yadav,Krishna Kumar Yadav,Fekri Abdulraqeb Ahmed Ali,Mansour Alhoshan,Marina Ms Cabral-Pinto

doi:10.3390/polym13020234

Abstract

Nano-fibrillated cellulose (NFC) was extracted by a chemical method involving alkali and acid hydrolysis. The characterisation of the citrus sinensis fruit peel bran and nano-fibrillated cellulose was performed by XRD, FTIR, TEM, and FESEM. XRD confirmed the phase of NFC which showed monoclinic crystal with spherical to rod shape morphology with a size of 44–50 nm. The crystallinity index of treated NFC increased from 39% to 75%. FTIR showed the removal of lignin and hemicellulose from waste peels due to the alkaline treatment. Silver nanoparticles were also synthesised by utilizing extract of citrus sinensis skins as a reducing agent. Pharmaceutical effluent samples from an industrial area were tested by Atomic Absorption Spectrometry. Out of the four metals obtained, cadmium and chromium were remediated by silver nanoparticles with nano-fibrillated cellulose via simulated method in 100 mg/L metal-salt concentrations over a time period of 160 min. The highest removal efficiency was found for cadmium, i.e., 83%, by using silver and NFC together as adsorbents. The second highest was for chromium, i.e., 47%, but by using only NFC. The Langmuir and Freundlich isotherms were well fitted for the sorption of Cd (II) and Cr (II) with suitable high R2 values during kinetic simulation. Thus, the isolation of NFC and synthesis of silver nanoparticles proved efficient for heavy metal sorption by the reuse of waste skins.

Highlights

The fruit of the citrus species Citrus × sinensis is sweet orange
The present study offers a simple and convenient method of synthesis of nanofibrillated cellulose from agricultural residues of fruit
Experimental results showed that produced nanocellulose had a diameter within the range of 44–50 nm

Summary

Introduction

The fruit of the citrus species Citrus × sinensis is sweet orange. Orange peel is a waste by-product from fruit juice factories across the world. Some of the novel methods for cellulose production include top-down methods that involve physical/enzymatic/chemical techniques for its isolation from agricultural/forest residue and wood, while bottom-up methods involve glucose bacteria to develop nanofibrillated cellulose [6,7]. These cellulosic materials with one of their dimensions in the nanometre range are termed generically as nanocelluloses. The main objective was value addition to this agricultural waste, which is at present thrown away after use in juice shops or factories This will open new avenues for using such abundant, renewable, and inexpensive agrowaste materials for developing value-added products. The total yield of bran obtained was found to be 52.10%

Chemical Treatment

Sorption Studies

Results and Discussion

Ag Nanoparticles

Conclusions