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Review
. 2020 Feb 17;10(12):7026-7047.
doi: 10.1039/c9ra10084a. eCollection 2020 Feb 13.

Recent advances in the use of walnut (Juglans regia L.) shell as a valuable plant-based bio-sorbent for the removal of hazardous materials

Ali Jahanban-Esfahlan  1   2 , Rana Jahanban-Esfahlan  3   4 , Mahnaz Tabibiazar  5   6 , Leila Roufegarinejad  7 , Ryszard Amarowicz  8
Affiliations
Review

Recent advances in the use of walnut (Juglans regia L.) shell as a valuable plant-based bio-sorbent for the removal of hazardous materials

Ali Jahanban-Esfahlan et al. RSC Adv. .

Abstract

The effective use of agricultural by-products is definitely a major challenge in waste management. In the walnut fruit processing industry, large amounts of shells are produced as agricultural by-products and discarded or burned produced as fuel. Walnut (Juglans regia L.) is a valuable tree nut in the Juglandaceae family. The fruit is composed of four main parts: the kernel, the skin, the shell, and the husk. The importance of walnuts is mostly related to theirs valuable kernels. However, their shells are currently experiencing as much interest as their kernels due to the beneficial effects of the shells. In the past several years, walnut shell (WS) has been widely explored as a naturally inert plant-based biosorbent. In this review, we first highlight recent scientific literature regarding the development of adsorbents from WS in the form of carbon-based materials including unmodified/modified WS, and activated carbons (ACs). Next, we discuss the potential applications of WS-derived by-products as natural yet effective adsorbents for the removal of various hazardous materials including heavy metals (HMs), synthetic industrial dyes, and harmful chemicals.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Fig. 1
Fig. 1. Different parts of walnut fruit and the corresponding by-products. The walnut fruit mainly consists of the husk, shell, skin, and kernel. The husk, shell and skin, are the main agricultural waste products of walnut fruit.
Fig. 2
Fig. 2. The chemical structures of several dyes removed by WS: RBR K-2BP, AR97, DAEA, MR GRL, CV, MEB, RB, RR2, MG, MB, and BG.
Fig. 3
Fig. 3. The chemical structures of some hazardous materials removed by the WS including CFX, EA, naphthalene, benzene, and MCP derivatives (2-CP, 3-CP, and 4-CP).
See this image and copyright information in PMC

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